LCOV - code coverage report
Current view: top level - src/backend/storage/lmgr - proc.c (source / functions) Hit Total Coverage
Test: PostgreSQL 18beta1 Lines: 524 569 92.1 %
Date: 2025-06-07 21:17:34 Functions: 28 28 100.0 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * proc.c
       4             :  *    routines to manage per-process shared memory data structure
       5             :  *
       6             :  * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
       7             :  * Portions Copyright (c) 1994, Regents of the University of California
       8             :  *
       9             :  *
      10             :  * IDENTIFICATION
      11             :  *    src/backend/storage/lmgr/proc.c
      12             :  *
      13             :  *-------------------------------------------------------------------------
      14             :  */
      15             : /*
      16             :  * Interface (a):
      17             :  *      JoinWaitQueue(), ProcSleep(), ProcWakeup()
      18             :  *
      19             :  * Waiting for a lock causes the backend to be put to sleep.  Whoever releases
      20             :  * the lock wakes the process up again (and gives it an error code so it knows
      21             :  * whether it was awoken on an error condition).
      22             :  *
      23             :  * Interface (b):
      24             :  *
      25             :  * ProcReleaseLocks -- frees the locks associated with current transaction
      26             :  *
      27             :  * ProcKill -- destroys the shared memory state (and locks)
      28             :  * associated with the process.
      29             :  */
      30             : #include "postgres.h"
      31             : 
      32             : #include <signal.h>
      33             : #include <unistd.h>
      34             : #include <sys/time.h>
      35             : 
      36             : #include "access/transam.h"
      37             : #include "access/twophase.h"
      38             : #include "access/xlogutils.h"
      39             : #include "miscadmin.h"
      40             : #include "pgstat.h"
      41             : #include "postmaster/autovacuum.h"
      42             : #include "replication/slotsync.h"
      43             : #include "replication/syncrep.h"
      44             : #include "storage/condition_variable.h"
      45             : #include "storage/ipc.h"
      46             : #include "storage/lmgr.h"
      47             : #include "storage/pmsignal.h"
      48             : #include "storage/proc.h"
      49             : #include "storage/procarray.h"
      50             : #include "storage/procsignal.h"
      51             : #include "storage/spin.h"
      52             : #include "storage/standby.h"
      53             : #include "utils/timeout.h"
      54             : #include "utils/timestamp.h"
      55             : 
      56             : /* GUC variables */
      57             : int         DeadlockTimeout = 1000;
      58             : int         StatementTimeout = 0;
      59             : int         LockTimeout = 0;
      60             : int         IdleInTransactionSessionTimeout = 0;
      61             : int         TransactionTimeout = 0;
      62             : int         IdleSessionTimeout = 0;
      63             : bool        log_lock_waits = false;
      64             : 
      65             : /* Pointer to this process's PGPROC struct, if any */
      66             : PGPROC     *MyProc = NULL;
      67             : 
      68             : /*
      69             :  * This spinlock protects the freelist of recycled PGPROC structures.
      70             :  * We cannot use an LWLock because the LWLock manager depends on already
      71             :  * having a PGPROC and a wait semaphore!  But these structures are touched
      72             :  * relatively infrequently (only at backend startup or shutdown) and not for
      73             :  * very long, so a spinlock is okay.
      74             :  */
      75             : NON_EXEC_STATIC slock_t *ProcStructLock = NULL;
      76             : 
      77             : /* Pointers to shared-memory structures */
      78             : PROC_HDR   *ProcGlobal = NULL;
      79             : NON_EXEC_STATIC PGPROC *AuxiliaryProcs = NULL;
      80             : PGPROC     *PreparedXactProcs = NULL;
      81             : 
      82             : static DeadLockState deadlock_state = DS_NOT_YET_CHECKED;
      83             : 
      84             : /* Is a deadlock check pending? */
      85             : static volatile sig_atomic_t got_deadlock_timeout;
      86             : 
      87             : static void RemoveProcFromArray(int code, Datum arg);
      88             : static void ProcKill(int code, Datum arg);
      89             : static void AuxiliaryProcKill(int code, Datum arg);
      90             : static void CheckDeadLock(void);
      91             : 
      92             : 
      93             : /*
      94             :  * Report shared-memory space needed by PGPROC.
      95             :  */
      96             : static Size
      97        5994 : PGProcShmemSize(void)
      98             : {
      99        5994 :     Size        size = 0;
     100             :     Size        TotalProcs =
     101        5994 :         add_size(MaxBackends, add_size(NUM_AUXILIARY_PROCS, max_prepared_xacts));
     102             : 
     103        5994 :     size = add_size(size, mul_size(TotalProcs, sizeof(PGPROC)));
     104        5994 :     size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->xids)));
     105        5994 :     size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->subxidStates)));
     106        5994 :     size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->statusFlags)));
     107             : 
     108        5994 :     return size;
     109             : }
     110             : 
     111             : /*
     112             :  * Report shared-memory space needed by Fast-Path locks.
     113             :  */
     114             : static Size
     115        5994 : FastPathLockShmemSize(void)
     116             : {
     117        5994 :     Size        size = 0;
     118             :     Size        TotalProcs =
     119        5994 :         add_size(MaxBackends, add_size(NUM_AUXILIARY_PROCS, max_prepared_xacts));
     120             :     Size        fpLockBitsSize,
     121             :                 fpRelIdSize;
     122             : 
     123             :     /*
     124             :      * Memory needed for PGPROC fast-path lock arrays. Make sure the sizes are
     125             :      * nicely aligned in each backend.
     126             :      */
     127        5994 :     fpLockBitsSize = MAXALIGN(FastPathLockGroupsPerBackend * sizeof(uint64));
     128        5994 :     fpRelIdSize = MAXALIGN(FastPathLockSlotsPerBackend() * sizeof(Oid));
     129             : 
     130        5994 :     size = add_size(size, mul_size(TotalProcs, (fpLockBitsSize + fpRelIdSize)));
     131             : 
     132        5994 :     return size;
     133             : }
     134             : 
     135             : /*
     136             :  * Report shared-memory space needed by InitProcGlobal.
     137             :  */
     138             : Size
     139        3898 : ProcGlobalShmemSize(void)
     140             : {
     141        3898 :     Size        size = 0;
     142             : 
     143             :     /* ProcGlobal */
     144        3898 :     size = add_size(size, sizeof(PROC_HDR));
     145        3898 :     size = add_size(size, sizeof(slock_t));
     146             : 
     147        3898 :     size = add_size(size, PGProcShmemSize());
     148        3898 :     size = add_size(size, FastPathLockShmemSize());
     149             : 
     150        3898 :     return size;
     151             : }
     152             : 
     153             : /*
     154             :  * Report number of semaphores needed by InitProcGlobal.
     155             :  */
     156             : int
     157        3898 : ProcGlobalSemas(void)
     158             : {
     159             :     /*
     160             :      * We need a sema per backend (including autovacuum), plus one for each
     161             :      * auxiliary process.
     162             :      */
     163        3898 :     return MaxBackends + NUM_AUXILIARY_PROCS;
     164             : }
     165             : 
     166             : /*
     167             :  * InitProcGlobal -
     168             :  *    Initialize the global process table during postmaster or standalone
     169             :  *    backend startup.
     170             :  *
     171             :  *    We also create all the per-process semaphores we will need to support
     172             :  *    the requested number of backends.  We used to allocate semaphores
     173             :  *    only when backends were actually started up, but that is bad because
     174             :  *    it lets Postgres fail under load --- a lot of Unix systems are
     175             :  *    (mis)configured with small limits on the number of semaphores, and
     176             :  *    running out when trying to start another backend is a common failure.
     177             :  *    So, now we grab enough semaphores to support the desired max number
     178             :  *    of backends immediately at initialization --- if the sysadmin has set
     179             :  *    MaxConnections, max_worker_processes, max_wal_senders, or
     180             :  *    autovacuum_worker_slots higher than his kernel will support, he'll
     181             :  *    find out sooner rather than later.
     182             :  *
     183             :  *    Another reason for creating semaphores here is that the semaphore
     184             :  *    implementation typically requires us to create semaphores in the
     185             :  *    postmaster, not in backends.
     186             :  *
     187             :  * Note: this is NOT called by individual backends under a postmaster,
     188             :  * not even in the EXEC_BACKEND case.  The ProcGlobal and AuxiliaryProcs
     189             :  * pointers must be propagated specially for EXEC_BACKEND operation.
     190             :  */
     191             : void
     192        2096 : InitProcGlobal(void)
     193             : {
     194             :     PGPROC     *procs;
     195             :     int         i,
     196             :                 j;
     197             :     bool        found;
     198        2096 :     uint32      TotalProcs = MaxBackends + NUM_AUXILIARY_PROCS + max_prepared_xacts;
     199             : 
     200             :     /* Used for setup of per-backend fast-path slots. */
     201             :     char       *fpPtr,
     202             :                *fpEndPtr PG_USED_FOR_ASSERTS_ONLY;
     203             :     Size        fpLockBitsSize,
     204             :                 fpRelIdSize;
     205             :     Size        requestSize;
     206             :     char       *ptr;
     207             : 
     208             :     /* Create the ProcGlobal shared structure */
     209        2096 :     ProcGlobal = (PROC_HDR *)
     210        2096 :         ShmemInitStruct("Proc Header", sizeof(PROC_HDR), &found);
     211             :     Assert(!found);
     212             : 
     213             :     /*
     214             :      * Initialize the data structures.
     215             :      */
     216        2096 :     ProcGlobal->spins_per_delay = DEFAULT_SPINS_PER_DELAY;
     217        2096 :     dlist_init(&ProcGlobal->freeProcs);
     218        2096 :     dlist_init(&ProcGlobal->autovacFreeProcs);
     219        2096 :     dlist_init(&ProcGlobal->bgworkerFreeProcs);
     220        2096 :     dlist_init(&ProcGlobal->walsenderFreeProcs);
     221        2096 :     ProcGlobal->startupBufferPinWaitBufId = -1;
     222        2096 :     ProcGlobal->walwriterProc = INVALID_PROC_NUMBER;
     223        2096 :     ProcGlobal->checkpointerProc = INVALID_PROC_NUMBER;
     224        2096 :     pg_atomic_init_u32(&ProcGlobal->procArrayGroupFirst, INVALID_PROC_NUMBER);
     225        2096 :     pg_atomic_init_u32(&ProcGlobal->clogGroupFirst, INVALID_PROC_NUMBER);
     226             : 
     227             :     /*
     228             :      * Create and initialize all the PGPROC structures we'll need.  There are
     229             :      * six separate consumers: (1) normal backends, (2) autovacuum workers and
     230             :      * special workers, (3) background workers, (4) walsenders, (5) auxiliary
     231             :      * processes, and (6) prepared transactions.  (For largely-historical
     232             :      * reasons, we combine autovacuum and special workers into one category
     233             :      * with a single freelist.)  Each PGPROC structure is dedicated to exactly
     234             :      * one of these purposes, and they do not move between groups.
     235             :      */
     236        2096 :     requestSize = PGProcShmemSize();
     237             : 
     238        2096 :     ptr = ShmemInitStruct("PGPROC structures",
     239             :                           requestSize,
     240             :                           &found);
     241             : 
     242        2096 :     MemSet(ptr, 0, requestSize);
     243             : 
     244        2096 :     procs = (PGPROC *) ptr;
     245        2096 :     ptr = (char *) ptr + TotalProcs * sizeof(PGPROC);
     246             : 
     247        2096 :     ProcGlobal->allProcs = procs;
     248             :     /* XXX allProcCount isn't really all of them; it excludes prepared xacts */
     249        2096 :     ProcGlobal->allProcCount = MaxBackends + NUM_AUXILIARY_PROCS;
     250             : 
     251             :     /*
     252             :      * Allocate arrays mirroring PGPROC fields in a dense manner. See
     253             :      * PROC_HDR.
     254             :      *
     255             :      * XXX: It might make sense to increase padding for these arrays, given
     256             :      * how hotly they are accessed.
     257             :      */
     258        2096 :     ProcGlobal->xids = (TransactionId *) ptr;
     259        2096 :     ptr = (char *) ptr + (TotalProcs * sizeof(*ProcGlobal->xids));
     260             : 
     261        2096 :     ProcGlobal->subxidStates = (XidCacheStatus *) ptr;
     262        2096 :     ptr = (char *) ptr + (TotalProcs * sizeof(*ProcGlobal->subxidStates));
     263             : 
     264        2096 :     ProcGlobal->statusFlags = (uint8 *) ptr;
     265        2096 :     ptr = (char *) ptr + (TotalProcs * sizeof(*ProcGlobal->statusFlags));
     266             : 
     267             :     /* make sure wer didn't overflow */
     268             :     Assert((ptr > (char *) procs) && (ptr <= (char *) procs + requestSize));
     269             : 
     270             :     /*
     271             :      * Allocate arrays for fast-path locks. Those are variable-length, so
     272             :      * can't be included in PGPROC directly. We allocate a separate piece of
     273             :      * shared memory and then divide that between backends.
     274             :      */
     275        2096 :     fpLockBitsSize = MAXALIGN(FastPathLockGroupsPerBackend * sizeof(uint64));
     276        2096 :     fpRelIdSize = MAXALIGN(FastPathLockSlotsPerBackend() * sizeof(Oid));
     277             : 
     278        2096 :     requestSize = FastPathLockShmemSize();
     279             : 
     280        2096 :     fpPtr = ShmemInitStruct("Fast-Path Lock Array",
     281             :                             requestSize,
     282             :                             &found);
     283             : 
     284        2096 :     MemSet(fpPtr, 0, requestSize);
     285             : 
     286             :     /* For asserts checking we did not overflow. */
     287        2096 :     fpEndPtr = fpPtr + requestSize;
     288             : 
     289      280528 :     for (i = 0; i < TotalProcs; i++)
     290             :     {
     291      278432 :         PGPROC     *proc = &procs[i];
     292             : 
     293             :         /* Common initialization for all PGPROCs, regardless of type. */
     294             : 
     295             :         /*
     296             :          * Set the fast-path lock arrays, and move the pointer. We interleave
     297             :          * the two arrays, to (hopefully) get some locality for each backend.
     298             :          */
     299      278432 :         proc->fpLockBits = (uint64 *) fpPtr;
     300      278432 :         fpPtr += fpLockBitsSize;
     301             : 
     302      278432 :         proc->fpRelId = (Oid *) fpPtr;
     303      278432 :         fpPtr += fpRelIdSize;
     304             : 
     305             :         Assert(fpPtr <= fpEndPtr);
     306             : 
     307             :         /*
     308             :          * Set up per-PGPROC semaphore, latch, and fpInfoLock.  Prepared xact
     309             :          * dummy PGPROCs don't need these though - they're never associated
     310             :          * with a real process
     311             :          */
     312      278432 :         if (i < MaxBackends + NUM_AUXILIARY_PROCS)
     313             :         {
     314      276750 :             proc->sem = PGSemaphoreCreate();
     315      276750 :             InitSharedLatch(&(proc->procLatch));
     316      276750 :             LWLockInitialize(&(proc->fpInfoLock), LWTRANCHE_LOCK_FASTPATH);
     317             :         }
     318             : 
     319             :         /*
     320             :          * Newly created PGPROCs for normal backends, autovacuum workers,
     321             :          * special workers, bgworkers, and walsenders must be queued up on the
     322             :          * appropriate free list.  Because there can only ever be a small,
     323             :          * fixed number of auxiliary processes, no free list is used in that
     324             :          * case; InitAuxiliaryProcess() instead uses a linear search.  PGPROCs
     325             :          * for prepared transactions are added to a free list by
     326             :          * TwoPhaseShmemInit().
     327             :          */
     328      278432 :         if (i < MaxConnections)
     329             :         {
     330             :             /* PGPROC for normal backend, add to freeProcs list */
     331      139282 :             dlist_push_tail(&ProcGlobal->freeProcs, &proc->links);
     332      139282 :             proc->procgloballist = &ProcGlobal->freeProcs;
     333             :         }
     334      139150 :         else if (i < MaxConnections + autovacuum_worker_slots + NUM_SPECIAL_WORKER_PROCS)
     335             :         {
     336             :             /* PGPROC for AV or special worker, add to autovacFreeProcs list */
     337       27640 :             dlist_push_tail(&ProcGlobal->autovacFreeProcs, &proc->links);
     338       27640 :             proc->procgloballist = &ProcGlobal->autovacFreeProcs;
     339             :         }
     340      111510 :         else if (i < MaxConnections + autovacuum_worker_slots + NUM_SPECIAL_WORKER_PROCS + max_worker_processes)
     341             :         {
     342             :             /* PGPROC for bgworker, add to bgworkerFreeProcs list */
     343       16764 :             dlist_push_tail(&ProcGlobal->bgworkerFreeProcs, &proc->links);
     344       16764 :             proc->procgloballist = &ProcGlobal->bgworkerFreeProcs;
     345             :         }
     346       94746 :         else if (i < MaxBackends)
     347             :         {
     348             :             /* PGPROC for walsender, add to walsenderFreeProcs list */
     349       13416 :             dlist_push_tail(&ProcGlobal->walsenderFreeProcs, &proc->links);
     350       13416 :             proc->procgloballist = &ProcGlobal->walsenderFreeProcs;
     351             :         }
     352             : 
     353             :         /* Initialize myProcLocks[] shared memory queues. */
     354     4733344 :         for (j = 0; j < NUM_LOCK_PARTITIONS; j++)
     355     4454912 :             dlist_init(&(proc->myProcLocks[j]));
     356             : 
     357             :         /* Initialize lockGroupMembers list. */
     358      278432 :         dlist_init(&proc->lockGroupMembers);
     359             : 
     360             :         /*
     361             :          * Initialize the atomic variables, otherwise, it won't be safe to
     362             :          * access them for backends that aren't currently in use.
     363             :          */
     364      278432 :         pg_atomic_init_u32(&(proc->procArrayGroupNext), INVALID_PROC_NUMBER);
     365      278432 :         pg_atomic_init_u32(&(proc->clogGroupNext), INVALID_PROC_NUMBER);
     366      278432 :         pg_atomic_init_u64(&(proc->waitStart), 0);
     367             :     }
     368             : 
     369             :     /* Should have consumed exactly the expected amount of fast-path memory. */
     370             :     Assert(fpPtr == fpEndPtr);
     371             : 
     372             :     /*
     373             :      * Save pointers to the blocks of PGPROC structures reserved for auxiliary
     374             :      * processes and prepared transactions.
     375             :      */
     376        2096 :     AuxiliaryProcs = &procs[MaxBackends];
     377        2096 :     PreparedXactProcs = &procs[MaxBackends + NUM_AUXILIARY_PROCS];
     378             : 
     379             :     /* Create ProcStructLock spinlock, too */
     380        2096 :     ProcStructLock = (slock_t *) ShmemInitStruct("ProcStructLock spinlock",
     381             :                                                  sizeof(slock_t),
     382             :                                                  &found);
     383        2096 :     SpinLockInit(ProcStructLock);
     384        2096 : }
     385             : 
     386             : /*
     387             :  * InitProcess -- initialize a per-process PGPROC entry for this backend
     388             :  */
     389             : void
     390       33660 : InitProcess(void)
     391             : {
     392             :     dlist_head *procgloballist;
     393             : 
     394             :     /*
     395             :      * ProcGlobal should be set up already (if we are a backend, we inherit
     396             :      * this by fork() or EXEC_BACKEND mechanism from the postmaster).
     397             :      */
     398       33660 :     if (ProcGlobal == NULL)
     399           0 :         elog(PANIC, "proc header uninitialized");
     400             : 
     401       33660 :     if (MyProc != NULL)
     402           0 :         elog(ERROR, "you already exist");
     403             : 
     404             :     /*
     405             :      * Before we start accessing the shared memory in a serious way, mark
     406             :      * ourselves as an active postmaster child; this is so that the postmaster
     407             :      * can detect it if we exit without cleaning up.
     408             :      */
     409       33660 :     if (IsUnderPostmaster)
     410       33446 :         RegisterPostmasterChildActive();
     411             : 
     412             :     /*
     413             :      * Decide which list should supply our PGPROC.  This logic must match the
     414             :      * way the freelists were constructed in InitProcGlobal().
     415             :      */
     416       33660 :     if (AmAutoVacuumWorkerProcess() || AmSpecialWorkerProcess())
     417        3942 :         procgloballist = &ProcGlobal->autovacFreeProcs;
     418       29718 :     else if (AmBackgroundWorkerProcess())
     419        4436 :         procgloballist = &ProcGlobal->bgworkerFreeProcs;
     420       25282 :     else if (AmWalSenderProcess())
     421        2200 :         procgloballist = &ProcGlobal->walsenderFreeProcs;
     422             :     else
     423       23082 :         procgloballist = &ProcGlobal->freeProcs;
     424             : 
     425             :     /*
     426             :      * Try to get a proc struct from the appropriate free list.  If this
     427             :      * fails, we must be out of PGPROC structures (not to mention semaphores).
     428             :      *
     429             :      * While we are holding the ProcStructLock, also copy the current shared
     430             :      * estimate of spins_per_delay to local storage.
     431             :      */
     432       33660 :     SpinLockAcquire(ProcStructLock);
     433             : 
     434       33660 :     set_spins_per_delay(ProcGlobal->spins_per_delay);
     435             : 
     436       33660 :     if (!dlist_is_empty(procgloballist))
     437             :     {
     438       33654 :         MyProc = dlist_container(PGPROC, links, dlist_pop_head_node(procgloballist));
     439       33654 :         SpinLockRelease(ProcStructLock);
     440             :     }
     441             :     else
     442             :     {
     443             :         /*
     444             :          * If we reach here, all the PGPROCs are in use.  This is one of the
     445             :          * possible places to detect "too many backends", so give the standard
     446             :          * error message.  XXX do we need to give a different failure message
     447             :          * in the autovacuum case?
     448             :          */
     449           6 :         SpinLockRelease(ProcStructLock);
     450           6 :         if (AmWalSenderProcess())
     451           4 :             ereport(FATAL,
     452             :                     (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
     453             :                      errmsg("number of requested standby connections exceeds \"max_wal_senders\" (currently %d)",
     454             :                             max_wal_senders)));
     455           2 :         ereport(FATAL,
     456             :                 (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
     457             :                  errmsg("sorry, too many clients already")));
     458             :     }
     459       33654 :     MyProcNumber = GetNumberFromPGProc(MyProc);
     460             : 
     461             :     /*
     462             :      * Cross-check that the PGPROC is of the type we expect; if this were not
     463             :      * the case, it would get returned to the wrong list.
     464             :      */
     465             :     Assert(MyProc->procgloballist == procgloballist);
     466             : 
     467             :     /*
     468             :      * Initialize all fields of MyProc, except for those previously
     469             :      * initialized by InitProcGlobal.
     470             :      */
     471       33654 :     dlist_node_init(&MyProc->links);
     472       33654 :     MyProc->waitStatus = PROC_WAIT_STATUS_OK;
     473       33654 :     MyProc->fpVXIDLock = false;
     474       33654 :     MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
     475       33654 :     MyProc->xid = InvalidTransactionId;
     476       33654 :     MyProc->xmin = InvalidTransactionId;
     477       33654 :     MyProc->pid = MyProcPid;
     478       33654 :     MyProc->vxid.procNumber = MyProcNumber;
     479       33654 :     MyProc->vxid.lxid = InvalidLocalTransactionId;
     480             :     /* databaseId and roleId will be filled in later */
     481       33654 :     MyProc->databaseId = InvalidOid;
     482       33654 :     MyProc->roleId = InvalidOid;
     483       33654 :     MyProc->tempNamespaceId = InvalidOid;
     484       33654 :     MyProc->isRegularBackend = AmRegularBackendProcess();
     485       33654 :     MyProc->delayChkptFlags = 0;
     486       33654 :     MyProc->statusFlags = 0;
     487             :     /* NB -- autovac launcher intentionally does not set IS_AUTOVACUUM */
     488       33654 :     if (AmAutoVacuumWorkerProcess())
     489        3186 :         MyProc->statusFlags |= PROC_IS_AUTOVACUUM;
     490       33654 :     MyProc->lwWaiting = LW_WS_NOT_WAITING;
     491       33654 :     MyProc->lwWaitMode = 0;
     492       33654 :     MyProc->waitLock = NULL;
     493       33654 :     MyProc->waitProcLock = NULL;
     494       33654 :     pg_atomic_write_u64(&MyProc->waitStart, 0);
     495             : #ifdef USE_ASSERT_CHECKING
     496             :     {
     497             :         int         i;
     498             : 
     499             :         /* Last process should have released all locks. */
     500             :         for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
     501             :             Assert(dlist_is_empty(&(MyProc->myProcLocks[i])));
     502             :     }
     503             : #endif
     504       33654 :     MyProc->recoveryConflictPending = false;
     505             : 
     506             :     /* Initialize fields for sync rep */
     507       33654 :     MyProc->waitLSN = 0;
     508       33654 :     MyProc->syncRepState = SYNC_REP_NOT_WAITING;
     509       33654 :     dlist_node_init(&MyProc->syncRepLinks);
     510             : 
     511             :     /* Initialize fields for group XID clearing. */
     512       33654 :     MyProc->procArrayGroupMember = false;
     513       33654 :     MyProc->procArrayGroupMemberXid = InvalidTransactionId;
     514             :     Assert(pg_atomic_read_u32(&MyProc->procArrayGroupNext) == INVALID_PROC_NUMBER);
     515             : 
     516             :     /* Check that group locking fields are in a proper initial state. */
     517             :     Assert(MyProc->lockGroupLeader == NULL);
     518             :     Assert(dlist_is_empty(&MyProc->lockGroupMembers));
     519             : 
     520             :     /* Initialize wait event information. */
     521       33654 :     MyProc->wait_event_info = 0;
     522             : 
     523             :     /* Initialize fields for group transaction status update. */
     524       33654 :     MyProc->clogGroupMember = false;
     525       33654 :     MyProc->clogGroupMemberXid = InvalidTransactionId;
     526       33654 :     MyProc->clogGroupMemberXidStatus = TRANSACTION_STATUS_IN_PROGRESS;
     527       33654 :     MyProc->clogGroupMemberPage = -1;
     528       33654 :     MyProc->clogGroupMemberLsn = InvalidXLogRecPtr;
     529             :     Assert(pg_atomic_read_u32(&MyProc->clogGroupNext) == INVALID_PROC_NUMBER);
     530             : 
     531             :     /*
     532             :      * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
     533             :      * on it.  That allows us to repoint the process latch, which so far
     534             :      * points to process local one, to the shared one.
     535             :      */
     536       33654 :     OwnLatch(&MyProc->procLatch);
     537       33654 :     SwitchToSharedLatch();
     538             : 
     539             :     /* now that we have a proc, report wait events to shared memory */
     540       33654 :     pgstat_set_wait_event_storage(&MyProc->wait_event_info);
     541             : 
     542             :     /*
     543             :      * We might be reusing a semaphore that belonged to a failed process. So
     544             :      * be careful and reinitialize its value here.  (This is not strictly
     545             :      * necessary anymore, but seems like a good idea for cleanliness.)
     546             :      */
     547       33654 :     PGSemaphoreReset(MyProc->sem);
     548             : 
     549             :     /*
     550             :      * Arrange to clean up at backend exit.
     551             :      */
     552       33654 :     on_shmem_exit(ProcKill, 0);
     553             : 
     554             :     /*
     555             :      * Now that we have a PGPROC, we could try to acquire locks, so initialize
     556             :      * local state needed for LWLocks, and the deadlock checker.
     557             :      */
     558       33654 :     InitLWLockAccess();
     559       33654 :     InitDeadLockChecking();
     560             : 
     561             : #ifdef EXEC_BACKEND
     562             : 
     563             :     /*
     564             :      * Initialize backend-local pointers to all the shared data structures.
     565             :      * (We couldn't do this until now because it needs LWLocks.)
     566             :      */
     567             :     if (IsUnderPostmaster)
     568             :         AttachSharedMemoryStructs();
     569             : #endif
     570       33654 : }
     571             : 
     572             : /*
     573             :  * InitProcessPhase2 -- make MyProc visible in the shared ProcArray.
     574             :  *
     575             :  * This is separate from InitProcess because we can't acquire LWLocks until
     576             :  * we've created a PGPROC, but in the EXEC_BACKEND case ProcArrayAdd won't
     577             :  * work until after we've done AttachSharedMemoryStructs.
     578             :  */
     579             : void
     580       33636 : InitProcessPhase2(void)
     581             : {
     582             :     Assert(MyProc != NULL);
     583             : 
     584             :     /*
     585             :      * Add our PGPROC to the PGPROC array in shared memory.
     586             :      */
     587       33636 :     ProcArrayAdd(MyProc);
     588             : 
     589             :     /*
     590             :      * Arrange to clean that up at backend exit.
     591             :      */
     592       33636 :     on_shmem_exit(RemoveProcFromArray, 0);
     593       33636 : }
     594             : 
     595             : /*
     596             :  * InitAuxiliaryProcess -- create a PGPROC entry for an auxiliary process
     597             :  *
     598             :  * This is called by bgwriter and similar processes so that they will have a
     599             :  * MyProc value that's real enough to let them wait for LWLocks.  The PGPROC
     600             :  * and sema that are assigned are one of the extra ones created during
     601             :  * InitProcGlobal.
     602             :  *
     603             :  * Auxiliary processes are presently not expected to wait for real (lockmgr)
     604             :  * locks, so we need not set up the deadlock checker.  They are never added
     605             :  * to the ProcArray or the sinval messaging mechanism, either.  They also
     606             :  * don't get a VXID assigned, since this is only useful when we actually
     607             :  * hold lockmgr locks.
     608             :  *
     609             :  * Startup process however uses locks but never waits for them in the
     610             :  * normal backend sense. Startup process also takes part in sinval messaging
     611             :  * as a sendOnly process, so never reads messages from sinval queue. So
     612             :  * Startup process does have a VXID and does show up in pg_locks.
     613             :  */
     614             : void
     615        8102 : InitAuxiliaryProcess(void)
     616             : {
     617             :     PGPROC     *auxproc;
     618             :     int         proctype;
     619             : 
     620             :     /*
     621             :      * ProcGlobal should be set up already (if we are a backend, we inherit
     622             :      * this by fork() or EXEC_BACKEND mechanism from the postmaster).
     623             :      */
     624        8102 :     if (ProcGlobal == NULL || AuxiliaryProcs == NULL)
     625           0 :         elog(PANIC, "proc header uninitialized");
     626             : 
     627        8102 :     if (MyProc != NULL)
     628           0 :         elog(ERROR, "you already exist");
     629             : 
     630        8102 :     if (IsUnderPostmaster)
     631        8102 :         RegisterPostmasterChildActive();
     632             : 
     633             :     /*
     634             :      * We use the ProcStructLock to protect assignment and releasing of
     635             :      * AuxiliaryProcs entries.
     636             :      *
     637             :      * While we are holding the ProcStructLock, also copy the current shared
     638             :      * estimate of spins_per_delay to local storage.
     639             :      */
     640        8102 :     SpinLockAcquire(ProcStructLock);
     641             : 
     642        8102 :     set_spins_per_delay(ProcGlobal->spins_per_delay);
     643             : 
     644             :     /*
     645             :      * Find a free auxproc ... *big* trouble if there isn't one ...
     646             :      */
     647       32032 :     for (proctype = 0; proctype < NUM_AUXILIARY_PROCS; proctype++)
     648             :     {
     649       32032 :         auxproc = &AuxiliaryProcs[proctype];
     650       32032 :         if (auxproc->pid == 0)
     651        8102 :             break;
     652             :     }
     653        8102 :     if (proctype >= NUM_AUXILIARY_PROCS)
     654             :     {
     655           0 :         SpinLockRelease(ProcStructLock);
     656           0 :         elog(FATAL, "all AuxiliaryProcs are in use");
     657             :     }
     658             : 
     659             :     /* Mark auxiliary proc as in use by me */
     660             :     /* use volatile pointer to prevent code rearrangement */
     661        8102 :     ((volatile PGPROC *) auxproc)->pid = MyProcPid;
     662             : 
     663        8102 :     SpinLockRelease(ProcStructLock);
     664             : 
     665        8102 :     MyProc = auxproc;
     666        8102 :     MyProcNumber = GetNumberFromPGProc(MyProc);
     667             : 
     668             :     /*
     669             :      * Initialize all fields of MyProc, except for those previously
     670             :      * initialized by InitProcGlobal.
     671             :      */
     672        8102 :     dlist_node_init(&MyProc->links);
     673        8102 :     MyProc->waitStatus = PROC_WAIT_STATUS_OK;
     674        8102 :     MyProc->fpVXIDLock = false;
     675        8102 :     MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
     676        8102 :     MyProc->xid = InvalidTransactionId;
     677        8102 :     MyProc->xmin = InvalidTransactionId;
     678        8102 :     MyProc->vxid.procNumber = INVALID_PROC_NUMBER;
     679        8102 :     MyProc->vxid.lxid = InvalidLocalTransactionId;
     680        8102 :     MyProc->databaseId = InvalidOid;
     681        8102 :     MyProc->roleId = InvalidOid;
     682        8102 :     MyProc->tempNamespaceId = InvalidOid;
     683        8102 :     MyProc->isRegularBackend = false;
     684        8102 :     MyProc->delayChkptFlags = 0;
     685        8102 :     MyProc->statusFlags = 0;
     686        8102 :     MyProc->lwWaiting = LW_WS_NOT_WAITING;
     687        8102 :     MyProc->lwWaitMode = 0;
     688        8102 :     MyProc->waitLock = NULL;
     689        8102 :     MyProc->waitProcLock = NULL;
     690        8102 :     pg_atomic_write_u64(&MyProc->waitStart, 0);
     691             : #ifdef USE_ASSERT_CHECKING
     692             :     {
     693             :         int         i;
     694             : 
     695             :         /* Last process should have released all locks. */
     696             :         for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
     697             :             Assert(dlist_is_empty(&(MyProc->myProcLocks[i])));
     698             :     }
     699             : #endif
     700             : 
     701             :     /*
     702             :      * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
     703             :      * on it.  That allows us to repoint the process latch, which so far
     704             :      * points to process local one, to the shared one.
     705             :      */
     706        8102 :     OwnLatch(&MyProc->procLatch);
     707        8102 :     SwitchToSharedLatch();
     708             : 
     709             :     /* now that we have a proc, report wait events to shared memory */
     710        8102 :     pgstat_set_wait_event_storage(&MyProc->wait_event_info);
     711             : 
     712             :     /* Check that group locking fields are in a proper initial state. */
     713             :     Assert(MyProc->lockGroupLeader == NULL);
     714             :     Assert(dlist_is_empty(&MyProc->lockGroupMembers));
     715             : 
     716             :     /*
     717             :      * We might be reusing a semaphore that belonged to a failed process. So
     718             :      * be careful and reinitialize its value here.  (This is not strictly
     719             :      * necessary anymore, but seems like a good idea for cleanliness.)
     720             :      */
     721        8102 :     PGSemaphoreReset(MyProc->sem);
     722             : 
     723             :     /*
     724             :      * Arrange to clean up at process exit.
     725             :      */
     726        8102 :     on_shmem_exit(AuxiliaryProcKill, Int32GetDatum(proctype));
     727             : 
     728             :     /*
     729             :      * Now that we have a PGPROC, we could try to acquire lightweight locks.
     730             :      * Initialize local state needed for them.  (Heavyweight locks cannot be
     731             :      * acquired in aux processes.)
     732             :      */
     733        8102 :     InitLWLockAccess();
     734             : 
     735             : #ifdef EXEC_BACKEND
     736             : 
     737             :     /*
     738             :      * Initialize backend-local pointers to all the shared data structures.
     739             :      * (We couldn't do this until now because it needs LWLocks.)
     740             :      */
     741             :     if (IsUnderPostmaster)
     742             :         AttachSharedMemoryStructs();
     743             : #endif
     744        8102 : }
     745             : 
     746             : /*
     747             :  * Used from bufmgr to share the value of the buffer that Startup waits on,
     748             :  * or to reset the value to "not waiting" (-1). This allows processing
     749             :  * of recovery conflicts for buffer pins. Set is made before backends look
     750             :  * at this value, so locking not required, especially since the set is
     751             :  * an atomic integer set operation.
     752             :  */
     753             : void
     754          44 : SetStartupBufferPinWaitBufId(int bufid)
     755             : {
     756             :     /* use volatile pointer to prevent code rearrangement */
     757          44 :     volatile PROC_HDR *procglobal = ProcGlobal;
     758             : 
     759          44 :     procglobal->startupBufferPinWaitBufId = bufid;
     760          44 : }
     761             : 
     762             : /*
     763             :  * Used by backends when they receive a request to check for buffer pin waits.
     764             :  */
     765             : int
     766          10 : GetStartupBufferPinWaitBufId(void)
     767             : {
     768             :     /* use volatile pointer to prevent code rearrangement */
     769          10 :     volatile PROC_HDR *procglobal = ProcGlobal;
     770             : 
     771          10 :     return procglobal->startupBufferPinWaitBufId;
     772             : }
     773             : 
     774             : /*
     775             :  * Check whether there are at least N free PGPROC objects.  If false is
     776             :  * returned, *nfree will be set to the number of free PGPROC objects.
     777             :  * Otherwise, *nfree will be set to n.
     778             :  *
     779             :  * Note: this is designed on the assumption that N will generally be small.
     780             :  */
     781             : bool
     782         464 : HaveNFreeProcs(int n, int *nfree)
     783             : {
     784             :     dlist_iter  iter;
     785             : 
     786             :     Assert(n > 0);
     787             :     Assert(nfree);
     788             : 
     789         464 :     SpinLockAcquire(ProcStructLock);
     790             : 
     791         464 :     *nfree = 0;
     792        1388 :     dlist_foreach(iter, &ProcGlobal->freeProcs)
     793             :     {
     794        1384 :         (*nfree)++;
     795        1384 :         if (*nfree == n)
     796         460 :             break;
     797             :     }
     798             : 
     799         464 :     SpinLockRelease(ProcStructLock);
     800             : 
     801         464 :     return (*nfree == n);
     802             : }
     803             : 
     804             : /*
     805             :  * Cancel any pending wait for lock, when aborting a transaction, and revert
     806             :  * any strong lock count acquisition for a lock being acquired.
     807             :  *
     808             :  * (Normally, this would only happen if we accept a cancel/die
     809             :  * interrupt while waiting; but an ereport(ERROR) before or during the lock
     810             :  * wait is within the realm of possibility, too.)
     811             :  */
     812             : void
     813     1083220 : LockErrorCleanup(void)
     814             : {
     815             :     LOCALLOCK  *lockAwaited;
     816             :     LWLock     *partitionLock;
     817             :     DisableTimeoutParams timeouts[2];
     818             : 
     819     1083220 :     HOLD_INTERRUPTS();
     820             : 
     821     1083220 :     AbortStrongLockAcquire();
     822             : 
     823             :     /* Nothing to do if we weren't waiting for a lock */
     824     1083220 :     lockAwaited = GetAwaitedLock();
     825     1083220 :     if (lockAwaited == NULL)
     826             :     {
     827     1083138 :         RESUME_INTERRUPTS();
     828     1083138 :         return;
     829             :     }
     830             : 
     831             :     /*
     832             :      * Turn off the deadlock and lock timeout timers, if they are still
     833             :      * running (see ProcSleep).  Note we must preserve the LOCK_TIMEOUT
     834             :      * indicator flag, since this function is executed before
     835             :      * ProcessInterrupts when responding to SIGINT; else we'd lose the
     836             :      * knowledge that the SIGINT came from a lock timeout and not an external
     837             :      * source.
     838             :      */
     839          82 :     timeouts[0].id = DEADLOCK_TIMEOUT;
     840          82 :     timeouts[0].keep_indicator = false;
     841          82 :     timeouts[1].id = LOCK_TIMEOUT;
     842          82 :     timeouts[1].keep_indicator = true;
     843          82 :     disable_timeouts(timeouts, 2);
     844             : 
     845             :     /* Unlink myself from the wait queue, if on it (might not be anymore!) */
     846          82 :     partitionLock = LockHashPartitionLock(lockAwaited->hashcode);
     847          82 :     LWLockAcquire(partitionLock, LW_EXCLUSIVE);
     848             : 
     849          82 :     if (!dlist_node_is_detached(&MyProc->links))
     850             :     {
     851             :         /* We could not have been granted the lock yet */
     852          82 :         RemoveFromWaitQueue(MyProc, lockAwaited->hashcode);
     853             :     }
     854             :     else
     855             :     {
     856             :         /*
     857             :          * Somebody kicked us off the lock queue already.  Perhaps they
     858             :          * granted us the lock, or perhaps they detected a deadlock. If they
     859             :          * did grant us the lock, we'd better remember it in our local lock
     860             :          * table.
     861             :          */
     862           0 :         if (MyProc->waitStatus == PROC_WAIT_STATUS_OK)
     863           0 :             GrantAwaitedLock();
     864             :     }
     865             : 
     866          82 :     ResetAwaitedLock();
     867             : 
     868          82 :     LWLockRelease(partitionLock);
     869             : 
     870          82 :     RESUME_INTERRUPTS();
     871             : }
     872             : 
     873             : 
     874             : /*
     875             :  * ProcReleaseLocks() -- release locks associated with current transaction
     876             :  *          at main transaction commit or abort
     877             :  *
     878             :  * At main transaction commit, we release standard locks except session locks.
     879             :  * At main transaction abort, we release all locks including session locks.
     880             :  *
     881             :  * Advisory locks are released only if they are transaction-level;
     882             :  * session-level holds remain, whether this is a commit or not.
     883             :  *
     884             :  * At subtransaction commit, we don't release any locks (so this func is not
     885             :  * needed at all); we will defer the releasing to the parent transaction.
     886             :  * At subtransaction abort, we release all locks held by the subtransaction;
     887             :  * this is implemented by retail releasing of the locks under control of
     888             :  * the ResourceOwner mechanism.
     889             :  */
     890             : void
     891     1023364 : ProcReleaseLocks(bool isCommit)
     892             : {
     893     1023364 :     if (!MyProc)
     894           0 :         return;
     895             :     /* If waiting, get off wait queue (should only be needed after error) */
     896     1023364 :     LockErrorCleanup();
     897             :     /* Release standard locks, including session-level if aborting */
     898     1023364 :     LockReleaseAll(DEFAULT_LOCKMETHOD, !isCommit);
     899             :     /* Release transaction-level advisory locks */
     900     1023364 :     LockReleaseAll(USER_LOCKMETHOD, false);
     901             : }
     902             : 
     903             : 
     904             : /*
     905             :  * RemoveProcFromArray() -- Remove this process from the shared ProcArray.
     906             :  */
     907             : static void
     908       33636 : RemoveProcFromArray(int code, Datum arg)
     909             : {
     910             :     Assert(MyProc != NULL);
     911       33636 :     ProcArrayRemove(MyProc, InvalidTransactionId);
     912       33636 : }
     913             : 
     914             : /*
     915             :  * ProcKill() -- Destroy the per-proc data structure for
     916             :  *      this process. Release any of its held LW locks.
     917             :  */
     918             : static void
     919       33654 : ProcKill(int code, Datum arg)
     920             : {
     921             :     PGPROC     *proc;
     922             :     dlist_head *procgloballist;
     923             : 
     924             :     Assert(MyProc != NULL);
     925             : 
     926             :     /* not safe if forked by system(), etc. */
     927       33654 :     if (MyProc->pid != (int) getpid())
     928           0 :         elog(PANIC, "ProcKill() called in child process");
     929             : 
     930             :     /* Make sure we're out of the sync rep lists */
     931       33654 :     SyncRepCleanupAtProcExit();
     932             : 
     933             : #ifdef USE_ASSERT_CHECKING
     934             :     {
     935             :         int         i;
     936             : 
     937             :         /* Last process should have released all locks. */
     938             :         for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
     939             :             Assert(dlist_is_empty(&(MyProc->myProcLocks[i])));
     940             :     }
     941             : #endif
     942             : 
     943             :     /*
     944             :      * Release any LW locks I am holding.  There really shouldn't be any, but
     945             :      * it's cheap to check again before we cut the knees off the LWLock
     946             :      * facility by releasing our PGPROC ...
     947             :      */
     948       33654 :     LWLockReleaseAll();
     949             : 
     950             :     /* Cancel any pending condition variable sleep, too */
     951       33654 :     ConditionVariableCancelSleep();
     952             : 
     953             :     /*
     954             :      * Detach from any lock group of which we are a member.  If the leader
     955             :      * exits before all other group members, its PGPROC will remain allocated
     956             :      * until the last group process exits; that process must return the
     957             :      * leader's PGPROC to the appropriate list.
     958             :      */
     959       33654 :     if (MyProc->lockGroupLeader != NULL)
     960             :     {
     961        2872 :         PGPROC     *leader = MyProc->lockGroupLeader;
     962        2872 :         LWLock     *leader_lwlock = LockHashPartitionLockByProc(leader);
     963             : 
     964        2872 :         LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
     965             :         Assert(!dlist_is_empty(&leader->lockGroupMembers));
     966        2872 :         dlist_delete(&MyProc->lockGroupLink);
     967        2872 :         if (dlist_is_empty(&leader->lockGroupMembers))
     968             :         {
     969         138 :             leader->lockGroupLeader = NULL;
     970         138 :             if (leader != MyProc)
     971             :             {
     972           0 :                 procgloballist = leader->procgloballist;
     973             : 
     974             :                 /* Leader exited first; return its PGPROC. */
     975           0 :                 SpinLockAcquire(ProcStructLock);
     976           0 :                 dlist_push_head(procgloballist, &leader->links);
     977           0 :                 SpinLockRelease(ProcStructLock);
     978             :             }
     979             :         }
     980        2734 :         else if (leader != MyProc)
     981        2734 :             MyProc->lockGroupLeader = NULL;
     982        2872 :         LWLockRelease(leader_lwlock);
     983             :     }
     984             : 
     985             :     /*
     986             :      * Reset MyLatch to the process local one.  This is so that signal
     987             :      * handlers et al can continue using the latch after the shared latch
     988             :      * isn't ours anymore.
     989             :      *
     990             :      * Similarly, stop reporting wait events to MyProc->wait_event_info.
     991             :      *
     992             :      * After that clear MyProc and disown the shared latch.
     993             :      */
     994       33654 :     SwitchBackToLocalLatch();
     995       33654 :     pgstat_reset_wait_event_storage();
     996             : 
     997       33654 :     proc = MyProc;
     998       33654 :     MyProc = NULL;
     999       33654 :     MyProcNumber = INVALID_PROC_NUMBER;
    1000       33654 :     DisownLatch(&proc->procLatch);
    1001             : 
    1002             :     /* Mark the proc no longer in use */
    1003       33654 :     proc->pid = 0;
    1004       33654 :     proc->vxid.procNumber = INVALID_PROC_NUMBER;
    1005       33654 :     proc->vxid.lxid = InvalidTransactionId;
    1006             : 
    1007       33654 :     procgloballist = proc->procgloballist;
    1008       33654 :     SpinLockAcquire(ProcStructLock);
    1009             : 
    1010             :     /*
    1011             :      * If we're still a member of a locking group, that means we're a leader
    1012             :      * which has somehow exited before its children.  The last remaining child
    1013             :      * will release our PGPROC.  Otherwise, release it now.
    1014             :      */
    1015       33654 :     if (proc->lockGroupLeader == NULL)
    1016             :     {
    1017             :         /* Since lockGroupLeader is NULL, lockGroupMembers should be empty. */
    1018             :         Assert(dlist_is_empty(&proc->lockGroupMembers));
    1019             : 
    1020             :         /* Return PGPROC structure (and semaphore) to appropriate freelist */
    1021       33654 :         dlist_push_tail(procgloballist, &proc->links);
    1022             :     }
    1023             : 
    1024             :     /* Update shared estimate of spins_per_delay */
    1025       33654 :     ProcGlobal->spins_per_delay = update_spins_per_delay(ProcGlobal->spins_per_delay);
    1026             : 
    1027       33654 :     SpinLockRelease(ProcStructLock);
    1028             : 
    1029             :     /* wake autovac launcher if needed -- see comments in FreeWorkerInfo */
    1030       33654 :     if (AutovacuumLauncherPid != 0)
    1031        3182 :         kill(AutovacuumLauncherPid, SIGUSR2);
    1032       33654 : }
    1033             : 
    1034             : /*
    1035             :  * AuxiliaryProcKill() -- Cut-down version of ProcKill for auxiliary
    1036             :  *      processes (bgwriter, etc).  The PGPROC and sema are not released, only
    1037             :  *      marked as not-in-use.
    1038             :  */
    1039             : static void
    1040        8102 : AuxiliaryProcKill(int code, Datum arg)
    1041             : {
    1042        8102 :     int         proctype = DatumGetInt32(arg);
    1043             :     PGPROC     *auxproc PG_USED_FOR_ASSERTS_ONLY;
    1044             :     PGPROC     *proc;
    1045             : 
    1046             :     Assert(proctype >= 0 && proctype < NUM_AUXILIARY_PROCS);
    1047             : 
    1048             :     /* not safe if forked by system(), etc. */
    1049        8102 :     if (MyProc->pid != (int) getpid())
    1050           0 :         elog(PANIC, "AuxiliaryProcKill() called in child process");
    1051             : 
    1052        8102 :     auxproc = &AuxiliaryProcs[proctype];
    1053             : 
    1054             :     Assert(MyProc == auxproc);
    1055             : 
    1056             :     /* Release any LW locks I am holding (see notes above) */
    1057        8102 :     LWLockReleaseAll();
    1058             : 
    1059             :     /* Cancel any pending condition variable sleep, too */
    1060        8102 :     ConditionVariableCancelSleep();
    1061             : 
    1062             :     /* look at the equivalent ProcKill() code for comments */
    1063        8102 :     SwitchBackToLocalLatch();
    1064        8102 :     pgstat_reset_wait_event_storage();
    1065             : 
    1066        8102 :     proc = MyProc;
    1067        8102 :     MyProc = NULL;
    1068        8102 :     MyProcNumber = INVALID_PROC_NUMBER;
    1069        8102 :     DisownLatch(&proc->procLatch);
    1070             : 
    1071        8102 :     SpinLockAcquire(ProcStructLock);
    1072             : 
    1073             :     /* Mark auxiliary proc no longer in use */
    1074        8102 :     proc->pid = 0;
    1075        8102 :     proc->vxid.procNumber = INVALID_PROC_NUMBER;
    1076        8102 :     proc->vxid.lxid = InvalidTransactionId;
    1077             : 
    1078             :     /* Update shared estimate of spins_per_delay */
    1079        8102 :     ProcGlobal->spins_per_delay = update_spins_per_delay(ProcGlobal->spins_per_delay);
    1080             : 
    1081        8102 :     SpinLockRelease(ProcStructLock);
    1082        8102 : }
    1083             : 
    1084             : /*
    1085             :  * AuxiliaryPidGetProc -- get PGPROC for an auxiliary process
    1086             :  * given its PID
    1087             :  *
    1088             :  * Returns NULL if not found.
    1089             :  */
    1090             : PGPROC *
    1091       11648 : AuxiliaryPidGetProc(int pid)
    1092             : {
    1093       11648 :     PGPROC     *result = NULL;
    1094             :     int         index;
    1095             : 
    1096       11648 :     if (pid == 0)               /* never match dummy PGPROCs */
    1097           6 :         return NULL;
    1098             : 
    1099       54068 :     for (index = 0; index < NUM_AUXILIARY_PROCS; index++)
    1100             :     {
    1101       54068 :         PGPROC     *proc = &AuxiliaryProcs[index];
    1102             : 
    1103       54068 :         if (proc->pid == pid)
    1104             :         {
    1105       11642 :             result = proc;
    1106       11642 :             break;
    1107             :         }
    1108             :     }
    1109       11642 :     return result;
    1110             : }
    1111             : 
    1112             : 
    1113             : /*
    1114             :  * JoinWaitQueue -- join the wait queue on the specified lock
    1115             :  *
    1116             :  * It's not actually guaranteed that we need to wait when this function is
    1117             :  * called, because it could be that when we try to find a position at which
    1118             :  * to insert ourself into the wait queue, we discover that we must be inserted
    1119             :  * ahead of everyone who wants a lock that conflict with ours. In that case,
    1120             :  * we get the lock immediately. Because of this, it's sensible for this function
    1121             :  * to have a dontWait argument, despite the name.
    1122             :  *
    1123             :  * On entry, the caller has already set up LOCK and PROCLOCK entries to
    1124             :  * reflect that we have "requested" the lock.  The caller is responsible for
    1125             :  * cleaning that up, if we end up not joining the queue after all.
    1126             :  *
    1127             :  * The lock table's partition lock must be held at entry, and is still held
    1128             :  * at exit.  The caller must release it before calling ProcSleep().
    1129             :  *
    1130             :  * Result is one of the following:
    1131             :  *
    1132             :  *  PROC_WAIT_STATUS_OK       - lock was immediately granted
    1133             :  *  PROC_WAIT_STATUS_WAITING  - joined the wait queue; call ProcSleep()
    1134             :  *  PROC_WAIT_STATUS_ERROR    - immediate deadlock was detected, or would
    1135             :  *                              need to wait and dontWait == true
    1136             :  *
    1137             :  * NOTES: The process queue is now a priority queue for locking.
    1138             :  */
    1139             : ProcWaitStatus
    1140        4296 : JoinWaitQueue(LOCALLOCK *locallock, LockMethod lockMethodTable, bool dontWait)
    1141             : {
    1142        4296 :     LOCKMODE    lockmode = locallock->tag.mode;
    1143        4296 :     LOCK       *lock = locallock->lock;
    1144        4296 :     PROCLOCK   *proclock = locallock->proclock;
    1145        4296 :     uint32      hashcode = locallock->hashcode;
    1146        4296 :     LWLock     *partitionLock PG_USED_FOR_ASSERTS_ONLY = LockHashPartitionLock(hashcode);
    1147        4296 :     dclist_head *waitQueue = &lock->waitProcs;
    1148        4296 :     PGPROC     *insert_before = NULL;
    1149             :     LOCKMASK    myProcHeldLocks;
    1150             :     LOCKMASK    myHeldLocks;
    1151        4296 :     bool        early_deadlock = false;
    1152        4296 :     PGPROC     *leader = MyProc->lockGroupLeader;
    1153             : 
    1154             :     Assert(LWLockHeldByMeInMode(partitionLock, LW_EXCLUSIVE));
    1155             : 
    1156             :     /*
    1157             :      * Set bitmask of locks this process already holds on this object.
    1158             :      */
    1159        4296 :     myHeldLocks = MyProc->heldLocks = proclock->holdMask;
    1160             : 
    1161             :     /*
    1162             :      * Determine which locks we're already holding.
    1163             :      *
    1164             :      * If group locking is in use, locks held by members of my locking group
    1165             :      * need to be included in myHeldLocks.  This is not required for relation
    1166             :      * extension lock which conflict among group members. However, including
    1167             :      * them in myHeldLocks will give group members the priority to get those
    1168             :      * locks as compared to other backends which are also trying to acquire
    1169             :      * those locks.  OTOH, we can avoid giving priority to group members for
    1170             :      * that kind of locks, but there doesn't appear to be a clear advantage of
    1171             :      * the same.
    1172             :      */
    1173        4296 :     myProcHeldLocks = proclock->holdMask;
    1174        4296 :     myHeldLocks = myProcHeldLocks;
    1175        4296 :     if (leader != NULL)
    1176             :     {
    1177             :         dlist_iter  iter;
    1178             : 
    1179          86 :         dlist_foreach(iter, &lock->procLocks)
    1180             :         {
    1181             :             PROCLOCK   *otherproclock;
    1182             : 
    1183          64 :             otherproclock = dlist_container(PROCLOCK, lockLink, iter.cur);
    1184             : 
    1185          64 :             if (otherproclock->groupLeader == leader)
    1186          30 :                 myHeldLocks |= otherproclock->holdMask;
    1187             :         }
    1188             :     }
    1189             : 
    1190             :     /*
    1191             :      * Determine where to add myself in the wait queue.
    1192             :      *
    1193             :      * Normally I should go at the end of the queue.  However, if I already
    1194             :      * hold locks that conflict with the request of any previous waiter, put
    1195             :      * myself in the queue just in front of the first such waiter. This is not
    1196             :      * a necessary step, since deadlock detection would move me to before that
    1197             :      * waiter anyway; but it's relatively cheap to detect such a conflict
    1198             :      * immediately, and avoid delaying till deadlock timeout.
    1199             :      *
    1200             :      * Special case: if I find I should go in front of some waiter, check to
    1201             :      * see if I conflict with already-held locks or the requests before that
    1202             :      * waiter.  If not, then just grant myself the requested lock immediately.
    1203             :      * This is the same as the test for immediate grant in LockAcquire, except
    1204             :      * we are only considering the part of the wait queue before my insertion
    1205             :      * point.
    1206             :      */
    1207        4296 :     if (myHeldLocks != 0 && !dclist_is_empty(waitQueue))
    1208             :     {
    1209          24 :         LOCKMASK    aheadRequests = 0;
    1210             :         dlist_iter  iter;
    1211             : 
    1212          24 :         dclist_foreach(iter, waitQueue)
    1213             :         {
    1214          24 :             PGPROC     *proc = dlist_container(PGPROC, links, iter.cur);
    1215             : 
    1216             :             /*
    1217             :              * If we're part of the same locking group as this waiter, its
    1218             :              * locks neither conflict with ours nor contribute to
    1219             :              * aheadRequests.
    1220             :              */
    1221          24 :             if (leader != NULL && leader == proc->lockGroupLeader)
    1222           0 :                 continue;
    1223             : 
    1224             :             /* Must he wait for me? */
    1225          24 :             if (lockMethodTable->conflictTab[proc->waitLockMode] & myHeldLocks)
    1226             :             {
    1227             :                 /* Must I wait for him ? */
    1228          24 :                 if (lockMethodTable->conflictTab[lockmode] & proc->heldLocks)
    1229             :                 {
    1230             :                     /*
    1231             :                      * Yes, so we have a deadlock.  Easiest way to clean up
    1232             :                      * correctly is to call RemoveFromWaitQueue(), but we
    1233             :                      * can't do that until we are *on* the wait queue. So, set
    1234             :                      * a flag to check below, and break out of loop.  Also,
    1235             :                      * record deadlock info for later message.
    1236             :                      */
    1237           2 :                     RememberSimpleDeadLock(MyProc, lockmode, lock, proc);
    1238           2 :                     early_deadlock = true;
    1239           2 :                     break;
    1240             :                 }
    1241             :                 /* I must go before this waiter.  Check special case. */
    1242          22 :                 if ((lockMethodTable->conflictTab[lockmode] & aheadRequests) == 0 &&
    1243          22 :                     !LockCheckConflicts(lockMethodTable, lockmode, lock,
    1244             :                                         proclock))
    1245             :                 {
    1246             :                     /* Skip the wait and just grant myself the lock. */
    1247          22 :                     GrantLock(lock, proclock, lockmode);
    1248          22 :                     return PROC_WAIT_STATUS_OK;
    1249             :                 }
    1250             : 
    1251             :                 /* Put myself into wait queue before conflicting process */
    1252           0 :                 insert_before = proc;
    1253           0 :                 break;
    1254             :             }
    1255             :             /* Nope, so advance to next waiter */
    1256           0 :             aheadRequests |= LOCKBIT_ON(proc->waitLockMode);
    1257             :         }
    1258             :     }
    1259             : 
    1260             :     /*
    1261             :      * If we detected deadlock, give up without waiting.  This must agree with
    1262             :      * CheckDeadLock's recovery code.
    1263             :      */
    1264        4274 :     if (early_deadlock)
    1265           2 :         return PROC_WAIT_STATUS_ERROR;
    1266             : 
    1267             :     /*
    1268             :      * At this point we know that we'd really need to sleep. If we've been
    1269             :      * commanded not to do that, bail out.
    1270             :      */
    1271        4272 :     if (dontWait)
    1272        1448 :         return PROC_WAIT_STATUS_ERROR;
    1273             : 
    1274             :     /*
    1275             :      * Insert self into queue, at the position determined above.
    1276             :      */
    1277        2824 :     if (insert_before)
    1278           0 :         dclist_insert_before(waitQueue, &insert_before->links, &MyProc->links);
    1279             :     else
    1280        2824 :         dclist_push_tail(waitQueue, &MyProc->links);
    1281             : 
    1282        2824 :     lock->waitMask |= LOCKBIT_ON(lockmode);
    1283             : 
    1284             :     /* Set up wait information in PGPROC object, too */
    1285        2824 :     MyProc->heldLocks = myProcHeldLocks;
    1286        2824 :     MyProc->waitLock = lock;
    1287        2824 :     MyProc->waitProcLock = proclock;
    1288        2824 :     MyProc->waitLockMode = lockmode;
    1289             : 
    1290        2824 :     MyProc->waitStatus = PROC_WAIT_STATUS_WAITING;
    1291             : 
    1292        2824 :     return PROC_WAIT_STATUS_WAITING;
    1293             : }
    1294             : 
    1295             : /*
    1296             :  * ProcSleep -- put process to sleep waiting on lock
    1297             :  *
    1298             :  * This must be called when JoinWaitQueue() returns PROC_WAIT_STATUS_WAITING.
    1299             :  * Returns after the lock has been granted, or if a deadlock is detected.  Can
    1300             :  * also bail out with ereport(ERROR), if some other error condition, or a
    1301             :  * timeout or cancellation is triggered.
    1302             :  *
    1303             :  * Result is one of the following:
    1304             :  *
    1305             :  *  PROC_WAIT_STATUS_OK      - lock was granted
    1306             :  *  PROC_WAIT_STATUS_ERROR   - a deadlock was detected
    1307             :  */
    1308             : ProcWaitStatus
    1309        2824 : ProcSleep(LOCALLOCK *locallock)
    1310             : {
    1311        2824 :     LOCKMODE    lockmode = locallock->tag.mode;
    1312        2824 :     LOCK       *lock = locallock->lock;
    1313        2824 :     uint32      hashcode = locallock->hashcode;
    1314        2824 :     LWLock     *partitionLock = LockHashPartitionLock(hashcode);
    1315        2824 :     TimestampTz standbyWaitStart = 0;
    1316        2824 :     bool        allow_autovacuum_cancel = true;
    1317        2824 :     bool        logged_recovery_conflict = false;
    1318             :     ProcWaitStatus myWaitStatus;
    1319             : 
    1320             :     /* The caller must've armed the on-error cleanup mechanism */
    1321             :     Assert(GetAwaitedLock() == locallock);
    1322             :     Assert(!LWLockHeldByMe(partitionLock));
    1323             : 
    1324             :     /*
    1325             :      * Now that we will successfully clean up after an ereport, it's safe to
    1326             :      * check to see if there's a buffer pin deadlock against the Startup
    1327             :      * process.  Of course, that's only necessary if we're doing Hot Standby
    1328             :      * and are not the Startup process ourselves.
    1329             :      */
    1330        2824 :     if (RecoveryInProgress() && !InRecovery)
    1331           2 :         CheckRecoveryConflictDeadlock();
    1332             : 
    1333             :     /* Reset deadlock_state before enabling the timeout handler */
    1334        2824 :     deadlock_state = DS_NOT_YET_CHECKED;
    1335        2824 :     got_deadlock_timeout = false;
    1336             : 
    1337             :     /*
    1338             :      * Set timer so we can wake up after awhile and check for a deadlock. If a
    1339             :      * deadlock is detected, the handler sets MyProc->waitStatus =
    1340             :      * PROC_WAIT_STATUS_ERROR, allowing us to know that we must report failure
    1341             :      * rather than success.
    1342             :      *
    1343             :      * By delaying the check until we've waited for a bit, we can avoid
    1344             :      * running the rather expensive deadlock-check code in most cases.
    1345             :      *
    1346             :      * If LockTimeout is set, also enable the timeout for that.  We can save a
    1347             :      * few cycles by enabling both timeout sources in one call.
    1348             :      *
    1349             :      * If InHotStandby we set lock waits slightly later for clarity with other
    1350             :      * code.
    1351             :      */
    1352        2824 :     if (!InHotStandby)
    1353             :     {
    1354        2822 :         if (LockTimeout > 0)
    1355             :         {
    1356             :             EnableTimeoutParams timeouts[2];
    1357             : 
    1358         242 :             timeouts[0].id = DEADLOCK_TIMEOUT;
    1359         242 :             timeouts[0].type = TMPARAM_AFTER;
    1360         242 :             timeouts[0].delay_ms = DeadlockTimeout;
    1361         242 :             timeouts[1].id = LOCK_TIMEOUT;
    1362         242 :             timeouts[1].type = TMPARAM_AFTER;
    1363         242 :             timeouts[1].delay_ms = LockTimeout;
    1364         242 :             enable_timeouts(timeouts, 2);
    1365             :         }
    1366             :         else
    1367        2580 :             enable_timeout_after(DEADLOCK_TIMEOUT, DeadlockTimeout);
    1368             : 
    1369             :         /*
    1370             :          * Use the current time obtained for the deadlock timeout timer as
    1371             :          * waitStart (i.e., the time when this process started waiting for the
    1372             :          * lock). Since getting the current time newly can cause overhead, we
    1373             :          * reuse the already-obtained time to avoid that overhead.
    1374             :          *
    1375             :          * Note that waitStart is updated without holding the lock table's
    1376             :          * partition lock, to avoid the overhead by additional lock
    1377             :          * acquisition. This can cause "waitstart" in pg_locks to become NULL
    1378             :          * for a very short period of time after the wait started even though
    1379             :          * "granted" is false. This is OK in practice because we can assume
    1380             :          * that users are likely to look at "waitstart" when waiting for the
    1381             :          * lock for a long time.
    1382             :          */
    1383        2822 :         pg_atomic_write_u64(&MyProc->waitStart,
    1384        2822 :                             get_timeout_start_time(DEADLOCK_TIMEOUT));
    1385             :     }
    1386           2 :     else if (log_recovery_conflict_waits)
    1387             :     {
    1388             :         /*
    1389             :          * Set the wait start timestamp if logging is enabled and in hot
    1390             :          * standby.
    1391             :          */
    1392           2 :         standbyWaitStart = GetCurrentTimestamp();
    1393             :     }
    1394             : 
    1395             :     /*
    1396             :      * If somebody wakes us between LWLockRelease and WaitLatch, the latch
    1397             :      * will not wait. But a set latch does not necessarily mean that the lock
    1398             :      * is free now, as there are many other sources for latch sets than
    1399             :      * somebody releasing the lock.
    1400             :      *
    1401             :      * We process interrupts whenever the latch has been set, so cancel/die
    1402             :      * interrupts are processed quickly. This means we must not mind losing
    1403             :      * control to a cancel/die interrupt here.  We don't, because we have no
    1404             :      * shared-state-change work to do after being granted the lock (the
    1405             :      * grantor did it all).  We do have to worry about canceling the deadlock
    1406             :      * timeout and updating the locallock table, but if we lose control to an
    1407             :      * error, LockErrorCleanup will fix that up.
    1408             :      */
    1409             :     do
    1410             :     {
    1411        5034 :         if (InHotStandby)
    1412             :         {
    1413           6 :             bool        maybe_log_conflict =
    1414           6 :                 (standbyWaitStart != 0 && !logged_recovery_conflict);
    1415             : 
    1416             :             /* Set a timer and wait for that or for the lock to be granted */
    1417           6 :             ResolveRecoveryConflictWithLock(locallock->tag.lock,
    1418             :                                             maybe_log_conflict);
    1419             : 
    1420             :             /*
    1421             :              * Emit the log message if the startup process is waiting longer
    1422             :              * than deadlock_timeout for recovery conflict on lock.
    1423             :              */
    1424           6 :             if (maybe_log_conflict)
    1425             :             {
    1426           2 :                 TimestampTz now = GetCurrentTimestamp();
    1427             : 
    1428           2 :                 if (TimestampDifferenceExceeds(standbyWaitStart, now,
    1429             :                                                DeadlockTimeout))
    1430             :                 {
    1431             :                     VirtualTransactionId *vxids;
    1432             :                     int         cnt;
    1433             : 
    1434           2 :                     vxids = GetLockConflicts(&locallock->tag.lock,
    1435             :                                              AccessExclusiveLock, &cnt);
    1436             : 
    1437             :                     /*
    1438             :                      * Log the recovery conflict and the list of PIDs of
    1439             :                      * backends holding the conflicting lock. Note that we do
    1440             :                      * logging even if there are no such backends right now
    1441             :                      * because the startup process here has already waited
    1442             :                      * longer than deadlock_timeout.
    1443             :                      */
    1444           2 :                     LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_LOCK,
    1445             :                                         standbyWaitStart, now,
    1446           2 :                                         cnt > 0 ? vxids : NULL, true);
    1447           2 :                     logged_recovery_conflict = true;
    1448             :                 }
    1449             :             }
    1450             :         }
    1451             :         else
    1452             :         {
    1453        5028 :             (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
    1454        5028 :                              PG_WAIT_LOCK | locallock->tag.lock.locktag_type);
    1455        5028 :             ResetLatch(MyLatch);
    1456             :             /* check for deadlocks first, as that's probably log-worthy */
    1457        5028 :             if (got_deadlock_timeout)
    1458             :             {
    1459          58 :                 CheckDeadLock();
    1460          58 :                 got_deadlock_timeout = false;
    1461             :             }
    1462        5028 :             CHECK_FOR_INTERRUPTS();
    1463             :         }
    1464             : 
    1465             :         /*
    1466             :          * waitStatus could change from PROC_WAIT_STATUS_WAITING to something
    1467             :          * else asynchronously.  Read it just once per loop to prevent
    1468             :          * surprising behavior (such as missing log messages).
    1469             :          */
    1470        4952 :         myWaitStatus = *((volatile ProcWaitStatus *) &MyProc->waitStatus);
    1471             : 
    1472             :         /*
    1473             :          * If we are not deadlocked, but are waiting on an autovacuum-induced
    1474             :          * task, send a signal to interrupt it.
    1475             :          */
    1476        4952 :         if (deadlock_state == DS_BLOCKED_BY_AUTOVACUUM && allow_autovacuum_cancel)
    1477             :         {
    1478           0 :             PGPROC     *autovac = GetBlockingAutoVacuumPgproc();
    1479             :             uint8       statusFlags;
    1480             :             uint8       lockmethod_copy;
    1481             :             LOCKTAG     locktag_copy;
    1482             : 
    1483             :             /*
    1484             :              * Grab info we need, then release lock immediately.  Note this
    1485             :              * coding means that there is a tiny chance that the process
    1486             :              * terminates its current transaction and starts a different one
    1487             :              * before we have a change to send the signal; the worst possible
    1488             :              * consequence is that a for-wraparound vacuum is canceled.  But
    1489             :              * that could happen in any case unless we were to do kill() with
    1490             :              * the lock held, which is much more undesirable.
    1491             :              */
    1492           0 :             LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
    1493           0 :             statusFlags = ProcGlobal->statusFlags[autovac->pgxactoff];
    1494           0 :             lockmethod_copy = lock->tag.locktag_lockmethodid;
    1495           0 :             locktag_copy = lock->tag;
    1496           0 :             LWLockRelease(ProcArrayLock);
    1497             : 
    1498             :             /*
    1499             :              * Only do it if the worker is not working to protect against Xid
    1500             :              * wraparound.
    1501             :              */
    1502           0 :             if ((statusFlags & PROC_IS_AUTOVACUUM) &&
    1503           0 :                 !(statusFlags & PROC_VACUUM_FOR_WRAPAROUND))
    1504             :             {
    1505           0 :                 int         pid = autovac->pid;
    1506             : 
    1507             :                 /* report the case, if configured to do so */
    1508           0 :                 if (message_level_is_interesting(DEBUG1))
    1509             :                 {
    1510             :                     StringInfoData locktagbuf;
    1511             :                     StringInfoData logbuf;  /* errdetail for server log */
    1512             : 
    1513           0 :                     initStringInfo(&locktagbuf);
    1514           0 :                     initStringInfo(&logbuf);
    1515           0 :                     DescribeLockTag(&locktagbuf, &locktag_copy);
    1516           0 :                     appendStringInfo(&logbuf,
    1517             :                                      "Process %d waits for %s on %s.",
    1518             :                                      MyProcPid,
    1519             :                                      GetLockmodeName(lockmethod_copy, lockmode),
    1520             :                                      locktagbuf.data);
    1521             : 
    1522           0 :                     ereport(DEBUG1,
    1523             :                             (errmsg_internal("sending cancel to blocking autovacuum PID %d",
    1524             :                                              pid),
    1525             :                              errdetail_log("%s", logbuf.data)));
    1526             : 
    1527           0 :                     pfree(locktagbuf.data);
    1528           0 :                     pfree(logbuf.data);
    1529             :                 }
    1530             : 
    1531             :                 /* send the autovacuum worker Back to Old Kent Road */
    1532           0 :                 if (kill(pid, SIGINT) < 0)
    1533             :                 {
    1534             :                     /*
    1535             :                      * There's a race condition here: once we release the
    1536             :                      * ProcArrayLock, it's possible for the autovac worker to
    1537             :                      * close up shop and exit before we can do the kill().
    1538             :                      * Therefore, we do not whinge about no-such-process.
    1539             :                      * Other errors such as EPERM could conceivably happen if
    1540             :                      * the kernel recycles the PID fast enough, but such cases
    1541             :                      * seem improbable enough that it's probably best to issue
    1542             :                      * a warning if we see some other errno.
    1543             :                      */
    1544           0 :                     if (errno != ESRCH)
    1545           0 :                         ereport(WARNING,
    1546             :                                 (errmsg("could not send signal to process %d: %m",
    1547             :                                         pid)));
    1548             :                 }
    1549             :             }
    1550             : 
    1551             :             /* prevent signal from being sent again more than once */
    1552           0 :             allow_autovacuum_cancel = false;
    1553             :         }
    1554             : 
    1555             :         /*
    1556             :          * If awoken after the deadlock check interrupt has run, and
    1557             :          * log_lock_waits is on, then report about the wait.
    1558             :          */
    1559        4952 :         if (log_lock_waits && deadlock_state != DS_NOT_YET_CHECKED)
    1560             :         {
    1561             :             StringInfoData buf,
    1562             :                         lock_waiters_sbuf,
    1563             :                         lock_holders_sbuf;
    1564             :             const char *modename;
    1565             :             long        secs;
    1566             :             int         usecs;
    1567             :             long        msecs;
    1568          40 :             int         lockHoldersNum = 0;
    1569             : 
    1570          40 :             initStringInfo(&buf);
    1571          40 :             initStringInfo(&lock_waiters_sbuf);
    1572          40 :             initStringInfo(&lock_holders_sbuf);
    1573             : 
    1574          40 :             DescribeLockTag(&buf, &locallock->tag.lock);
    1575          40 :             modename = GetLockmodeName(locallock->tag.lock.locktag_lockmethodid,
    1576             :                                        lockmode);
    1577          40 :             TimestampDifference(get_timeout_start_time(DEADLOCK_TIMEOUT),
    1578             :                                 GetCurrentTimestamp(),
    1579             :                                 &secs, &usecs);
    1580          40 :             msecs = secs * 1000 + usecs / 1000;
    1581          40 :             usecs = usecs % 1000;
    1582             : 
    1583             :             /* Gather a list of all lock holders and waiters */
    1584          40 :             LWLockAcquire(partitionLock, LW_SHARED);
    1585          40 :             GetLockHoldersAndWaiters(locallock, &lock_holders_sbuf,
    1586             :                                      &lock_waiters_sbuf, &lockHoldersNum);
    1587          40 :             LWLockRelease(partitionLock);
    1588             : 
    1589          40 :             if (deadlock_state == DS_SOFT_DEADLOCK)
    1590           6 :                 ereport(LOG,
    1591             :                         (errmsg("process %d avoided deadlock for %s on %s by rearranging queue order after %ld.%03d ms",
    1592             :                                 MyProcPid, modename, buf.data, msecs, usecs),
    1593             :                          (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
    1594             :                                                "Processes holding the lock: %s. Wait queue: %s.",
    1595             :                                                lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
    1596          34 :             else if (deadlock_state == DS_HARD_DEADLOCK)
    1597             :             {
    1598             :                 /*
    1599             :                  * This message is a bit redundant with the error that will be
    1600             :                  * reported subsequently, but in some cases the error report
    1601             :                  * might not make it to the log (eg, if it's caught by an
    1602             :                  * exception handler), and we want to ensure all long-wait
    1603             :                  * events get logged.
    1604             :                  */
    1605           4 :                 ereport(LOG,
    1606             :                         (errmsg("process %d detected deadlock while waiting for %s on %s after %ld.%03d ms",
    1607             :                                 MyProcPid, modename, buf.data, msecs, usecs),
    1608             :                          (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
    1609             :                                                "Processes holding the lock: %s. Wait queue: %s.",
    1610             :                                                lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
    1611             :             }
    1612             : 
    1613          40 :             if (myWaitStatus == PROC_WAIT_STATUS_WAITING)
    1614          20 :                 ereport(LOG,
    1615             :                         (errmsg("process %d still waiting for %s on %s after %ld.%03d ms",
    1616             :                                 MyProcPid, modename, buf.data, msecs, usecs),
    1617             :                          (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
    1618             :                                                "Processes holding the lock: %s. Wait queue: %s.",
    1619             :                                                lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
    1620          20 :             else if (myWaitStatus == PROC_WAIT_STATUS_OK)
    1621          16 :                 ereport(LOG,
    1622             :                         (errmsg("process %d acquired %s on %s after %ld.%03d ms",
    1623             :                                 MyProcPid, modename, buf.data, msecs, usecs)));
    1624             :             else
    1625             :             {
    1626             :                 Assert(myWaitStatus == PROC_WAIT_STATUS_ERROR);
    1627             : 
    1628             :                 /*
    1629             :                  * Currently, the deadlock checker always kicks its own
    1630             :                  * process, which means that we'll only see
    1631             :                  * PROC_WAIT_STATUS_ERROR when deadlock_state ==
    1632             :                  * DS_HARD_DEADLOCK, and there's no need to print redundant
    1633             :                  * messages.  But for completeness and future-proofing, print
    1634             :                  * a message if it looks like someone else kicked us off the
    1635             :                  * lock.
    1636             :                  */
    1637           4 :                 if (deadlock_state != DS_HARD_DEADLOCK)
    1638           0 :                     ereport(LOG,
    1639             :                             (errmsg("process %d failed to acquire %s on %s after %ld.%03d ms",
    1640             :                                     MyProcPid, modename, buf.data, msecs, usecs),
    1641             :                              (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
    1642             :                                                    "Processes holding the lock: %s. Wait queue: %s.",
    1643             :                                                    lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
    1644             :             }
    1645             : 
    1646             :             /*
    1647             :              * At this point we might still need to wait for the lock. Reset
    1648             :              * state so we don't print the above messages again.
    1649             :              */
    1650          40 :             deadlock_state = DS_NO_DEADLOCK;
    1651             : 
    1652          40 :             pfree(buf.data);
    1653          40 :             pfree(lock_holders_sbuf.data);
    1654          40 :             pfree(lock_waiters_sbuf.data);
    1655             :         }
    1656        4952 :     } while (myWaitStatus == PROC_WAIT_STATUS_WAITING);
    1657             : 
    1658             :     /*
    1659             :      * Disable the timers, if they are still running.  As in LockErrorCleanup,
    1660             :      * we must preserve the LOCK_TIMEOUT indicator flag: if a lock timeout has
    1661             :      * already caused QueryCancelPending to become set, we want the cancel to
    1662             :      * be reported as a lock timeout, not a user cancel.
    1663             :      */
    1664        2742 :     if (!InHotStandby)
    1665             :     {
    1666        2740 :         if (LockTimeout > 0)
    1667             :         {
    1668             :             DisableTimeoutParams timeouts[2];
    1669             : 
    1670         230 :             timeouts[0].id = DEADLOCK_TIMEOUT;
    1671         230 :             timeouts[0].keep_indicator = false;
    1672         230 :             timeouts[1].id = LOCK_TIMEOUT;
    1673         230 :             timeouts[1].keep_indicator = true;
    1674         230 :             disable_timeouts(timeouts, 2);
    1675             :         }
    1676             :         else
    1677        2510 :             disable_timeout(DEADLOCK_TIMEOUT, false);
    1678             :     }
    1679             : 
    1680             :     /*
    1681             :      * Emit the log message if recovery conflict on lock was resolved but the
    1682             :      * startup process waited longer than deadlock_timeout for it.
    1683             :      */
    1684        2742 :     if (InHotStandby && logged_recovery_conflict)
    1685           2 :         LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_LOCK,
    1686             :                             standbyWaitStart, GetCurrentTimestamp(),
    1687             :                             NULL, false);
    1688             : 
    1689             :     /*
    1690             :      * We don't have to do anything else, because the awaker did all the
    1691             :      * necessary updates of the lock table and MyProc. (The caller is
    1692             :      * responsible for updating the local lock table.)
    1693             :      */
    1694        2742 :     return myWaitStatus;
    1695             : }
    1696             : 
    1697             : 
    1698             : /*
    1699             :  * ProcWakeup -- wake up a process by setting its latch.
    1700             :  *
    1701             :  *   Also remove the process from the wait queue and set its links invalid.
    1702             :  *
    1703             :  * The appropriate lock partition lock must be held by caller.
    1704             :  *
    1705             :  * XXX: presently, this code is only used for the "success" case, and only
    1706             :  * works correctly for that case.  To clean up in failure case, would need
    1707             :  * to twiddle the lock's request counts too --- see RemoveFromWaitQueue.
    1708             :  * Hence, in practice the waitStatus parameter must be PROC_WAIT_STATUS_OK.
    1709             :  */
    1710             : void
    1711        2758 : ProcWakeup(PGPROC *proc, ProcWaitStatus waitStatus)
    1712             : {
    1713        2758 :     if (dlist_node_is_detached(&proc->links))
    1714           0 :         return;
    1715             : 
    1716             :     Assert(proc->waitStatus == PROC_WAIT_STATUS_WAITING);
    1717             : 
    1718             :     /* Remove process from wait queue */
    1719        2758 :     dclist_delete_from_thoroughly(&proc->waitLock->waitProcs, &proc->links);
    1720             : 
    1721             :     /* Clean up process' state and pass it the ok/fail signal */
    1722        2758 :     proc->waitLock = NULL;
    1723        2758 :     proc->waitProcLock = NULL;
    1724        2758 :     proc->waitStatus = waitStatus;
    1725        2758 :     pg_atomic_write_u64(&MyProc->waitStart, 0);
    1726             : 
    1727             :     /* And awaken it */
    1728        2758 :     SetLatch(&proc->procLatch);
    1729             : }
    1730             : 
    1731             : /*
    1732             :  * ProcLockWakeup -- routine for waking up processes when a lock is
    1733             :  *      released (or a prior waiter is aborted).  Scan all waiters
    1734             :  *      for lock, waken any that are no longer blocked.
    1735             :  *
    1736             :  * The appropriate lock partition lock must be held by caller.
    1737             :  */
    1738             : void
    1739        2794 : ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock)
    1740             : {
    1741        2794 :     dclist_head *waitQueue = &lock->waitProcs;
    1742        2794 :     LOCKMASK    aheadRequests = 0;
    1743             :     dlist_mutable_iter miter;
    1744             : 
    1745        2794 :     if (dclist_is_empty(waitQueue))
    1746          92 :         return;
    1747             : 
    1748        6472 :     dclist_foreach_modify(miter, waitQueue)
    1749             :     {
    1750        3770 :         PGPROC     *proc = dlist_container(PGPROC, links, miter.cur);
    1751        3770 :         LOCKMODE    lockmode = proc->waitLockMode;
    1752             : 
    1753             :         /*
    1754             :          * Waken if (a) doesn't conflict with requests of earlier waiters, and
    1755             :          * (b) doesn't conflict with already-held locks.
    1756             :          */
    1757        3770 :         if ((lockMethodTable->conflictTab[lockmode] & aheadRequests) == 0 &&
    1758        3234 :             !LockCheckConflicts(lockMethodTable, lockmode, lock,
    1759             :                                 proc->waitProcLock))
    1760             :         {
    1761             :             /* OK to waken */
    1762        2758 :             GrantLock(lock, proc->waitProcLock, lockmode);
    1763             :             /* removes proc from the lock's waiting process queue */
    1764        2758 :             ProcWakeup(proc, PROC_WAIT_STATUS_OK);
    1765             :         }
    1766             :         else
    1767             :         {
    1768             :             /*
    1769             :              * Lock conflicts: Don't wake, but remember requested mode for
    1770             :              * later checks.
    1771             :              */
    1772        1012 :             aheadRequests |= LOCKBIT_ON(lockmode);
    1773             :         }
    1774             :     }
    1775             : }
    1776             : 
    1777             : /*
    1778             :  * CheckDeadLock
    1779             :  *
    1780             :  * We only get to this routine, if DEADLOCK_TIMEOUT fired while waiting for a
    1781             :  * lock to be released by some other process.  Check if there's a deadlock; if
    1782             :  * not, just return.  (But signal ProcSleep to log a message, if
    1783             :  * log_lock_waits is true.)  If we have a real deadlock, remove ourselves from
    1784             :  * the lock's wait queue and signal an error to ProcSleep.
    1785             :  */
    1786             : static void
    1787          58 : CheckDeadLock(void)
    1788             : {
    1789             :     int         i;
    1790             : 
    1791             :     /*
    1792             :      * Acquire exclusive lock on the entire shared lock data structures. Must
    1793             :      * grab LWLocks in partition-number order to avoid LWLock deadlock.
    1794             :      *
    1795             :      * Note that the deadlock check interrupt had better not be enabled
    1796             :      * anywhere that this process itself holds lock partition locks, else this
    1797             :      * will wait forever.  Also note that LWLockAcquire creates a critical
    1798             :      * section, so that this routine cannot be interrupted by cancel/die
    1799             :      * interrupts.
    1800             :      */
    1801         986 :     for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
    1802         928 :         LWLockAcquire(LockHashPartitionLockByIndex(i), LW_EXCLUSIVE);
    1803             : 
    1804             :     /*
    1805             :      * Check to see if we've been awoken by anyone in the interim.
    1806             :      *
    1807             :      * If we have, we can return and resume our transaction -- happy day.
    1808             :      * Before we are awoken the process releasing the lock grants it to us so
    1809             :      * we know that we don't have to wait anymore.
    1810             :      *
    1811             :      * We check by looking to see if we've been unlinked from the wait queue.
    1812             :      * This is safe because we hold the lock partition lock.
    1813             :      */
    1814          58 :     if (MyProc->links.prev == NULL ||
    1815          58 :         MyProc->links.next == NULL)
    1816           0 :         goto check_done;
    1817             : 
    1818             : #ifdef LOCK_DEBUG
    1819             :     if (Debug_deadlocks)
    1820             :         DumpAllLocks();
    1821             : #endif
    1822             : 
    1823             :     /* Run the deadlock check, and set deadlock_state for use by ProcSleep */
    1824          58 :     deadlock_state = DeadLockCheck(MyProc);
    1825             : 
    1826          58 :     if (deadlock_state == DS_HARD_DEADLOCK)
    1827             :     {
    1828             :         /*
    1829             :          * Oops.  We have a deadlock.
    1830             :          *
    1831             :          * Get this process out of wait state. (Note: we could do this more
    1832             :          * efficiently by relying on lockAwaited, but use this coding to
    1833             :          * preserve the flexibility to kill some other transaction than the
    1834             :          * one detecting the deadlock.)
    1835             :          *
    1836             :          * RemoveFromWaitQueue sets MyProc->waitStatus to
    1837             :          * PROC_WAIT_STATUS_ERROR, so ProcSleep will report an error after we
    1838             :          * return from the signal handler.
    1839             :          */
    1840             :         Assert(MyProc->waitLock != NULL);
    1841          10 :         RemoveFromWaitQueue(MyProc, LockTagHashCode(&(MyProc->waitLock->tag)));
    1842             : 
    1843             :         /*
    1844             :          * We're done here.  Transaction abort caused by the error that
    1845             :          * ProcSleep will raise will cause any other locks we hold to be
    1846             :          * released, thus allowing other processes to wake up; we don't need
    1847             :          * to do that here.  NOTE: an exception is that releasing locks we
    1848             :          * hold doesn't consider the possibility of waiters that were blocked
    1849             :          * behind us on the lock we just failed to get, and might now be
    1850             :          * wakable because we're not in front of them anymore.  However,
    1851             :          * RemoveFromWaitQueue took care of waking up any such processes.
    1852             :          */
    1853             :     }
    1854             : 
    1855             :     /*
    1856             :      * And release locks.  We do this in reverse order for two reasons: (1)
    1857             :      * Anyone else who needs more than one of the locks will be trying to lock
    1858             :      * them in increasing order; we don't want to release the other process
    1859             :      * until it can get all the locks it needs. (2) This avoids O(N^2)
    1860             :      * behavior inside LWLockRelease.
    1861             :      */
    1862          48 : check_done:
    1863         986 :     for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
    1864         928 :         LWLockRelease(LockHashPartitionLockByIndex(i));
    1865          58 : }
    1866             : 
    1867             : /*
    1868             :  * CheckDeadLockAlert - Handle the expiry of deadlock_timeout.
    1869             :  *
    1870             :  * NB: Runs inside a signal handler, be careful.
    1871             :  */
    1872             : void
    1873          58 : CheckDeadLockAlert(void)
    1874             : {
    1875          58 :     int         save_errno = errno;
    1876             : 
    1877          58 :     got_deadlock_timeout = true;
    1878             : 
    1879             :     /*
    1880             :      * Have to set the latch again, even if handle_sig_alarm already did. Back
    1881             :      * then got_deadlock_timeout wasn't yet set... It's unlikely that this
    1882             :      * ever would be a problem, but setting a set latch again is cheap.
    1883             :      *
    1884             :      * Note that, when this function runs inside procsignal_sigusr1_handler(),
    1885             :      * the handler function sets the latch again after the latch is set here.
    1886             :      */
    1887          58 :     SetLatch(MyLatch);
    1888          58 :     errno = save_errno;
    1889          58 : }
    1890             : 
    1891             : /*
    1892             :  * GetLockHoldersAndWaiters - get lock holders and waiters for a lock
    1893             :  *
    1894             :  * Fill lock_holders_sbuf and lock_waiters_sbuf with the PIDs of processes holding
    1895             :  * and waiting for the lock, and set lockHoldersNum to the number of lock holders.
    1896             :  *
    1897             :  * The lock table's partition lock must be held on entry and remains held on exit.
    1898             :  */
    1899             : void
    1900          40 : GetLockHoldersAndWaiters(LOCALLOCK *locallock, StringInfo lock_holders_sbuf,
    1901             :                          StringInfo lock_waiters_sbuf, int *lockHoldersNum)
    1902             : {
    1903             :     dlist_iter  proc_iter;
    1904             :     PROCLOCK   *curproclock;
    1905          40 :     LOCK       *lock = locallock->lock;
    1906          40 :     bool        first_holder = true,
    1907          40 :                 first_waiter = true;
    1908             : 
    1909             : #ifdef USE_ASSERT_CHECKING
    1910             :     {
    1911             :         uint32      hashcode = locallock->hashcode;
    1912             :         LWLock     *partitionLock = LockHashPartitionLock(hashcode);
    1913             : 
    1914             :         Assert(LWLockHeldByMe(partitionLock));
    1915             :     }
    1916             : #endif
    1917             : 
    1918          40 :     *lockHoldersNum = 0;
    1919             : 
    1920             :     /*
    1921             :      * Loop over the lock's procLocks to gather a list of all holders and
    1922             :      * waiters. Thus we will be able to provide more detailed information for
    1923             :      * lock debugging purposes.
    1924             :      *
    1925             :      * lock->procLocks contains all processes which hold or wait for this
    1926             :      * lock.
    1927             :      */
    1928         128 :     dlist_foreach(proc_iter, &lock->procLocks)
    1929             :     {
    1930          88 :         curproclock =
    1931          88 :             dlist_container(PROCLOCK, lockLink, proc_iter.cur);
    1932             : 
    1933             :         /*
    1934             :          * We are a waiter if myProc->waitProcLock == curproclock; we are a
    1935             :          * holder if it is NULL or something different.
    1936             :          */
    1937          88 :         if (curproclock->tag.myProc->waitProcLock == curproclock)
    1938             :         {
    1939          42 :             if (first_waiter)
    1940             :             {
    1941          22 :                 appendStringInfo(lock_waiters_sbuf, "%d",
    1942          22 :                                  curproclock->tag.myProc->pid);
    1943          22 :                 first_waiter = false;
    1944             :             }
    1945             :             else
    1946          20 :                 appendStringInfo(lock_waiters_sbuf, ", %d",
    1947          20 :                                  curproclock->tag.myProc->pid);
    1948             :         }
    1949             :         else
    1950             :         {
    1951          46 :             if (first_holder)
    1952             :             {
    1953          40 :                 appendStringInfo(lock_holders_sbuf, "%d",
    1954          40 :                                  curproclock->tag.myProc->pid);
    1955          40 :                 first_holder = false;
    1956             :             }
    1957             :             else
    1958           6 :                 appendStringInfo(lock_holders_sbuf, ", %d",
    1959           6 :                                  curproclock->tag.myProc->pid);
    1960             : 
    1961          46 :             (*lockHoldersNum)++;
    1962             :         }
    1963             :     }
    1964          40 : }
    1965             : 
    1966             : /*
    1967             :  * ProcWaitForSignal - wait for a signal from another backend.
    1968             :  *
    1969             :  * As this uses the generic process latch the caller has to be robust against
    1970             :  * unrelated wakeups: Always check that the desired state has occurred, and
    1971             :  * wait again if not.
    1972             :  */
    1973             : void
    1974          34 : ProcWaitForSignal(uint32 wait_event_info)
    1975             : {
    1976          34 :     (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
    1977             :                      wait_event_info);
    1978          34 :     ResetLatch(MyLatch);
    1979          34 :     CHECK_FOR_INTERRUPTS();
    1980          34 : }
    1981             : 
    1982             : /*
    1983             :  * ProcSendSignal - set the latch of a backend identified by ProcNumber
    1984             :  */
    1985             : void
    1986           8 : ProcSendSignal(ProcNumber procNumber)
    1987             : {
    1988           8 :     if (procNumber < 0 || procNumber >= ProcGlobal->allProcCount)
    1989           0 :         elog(ERROR, "procNumber out of range");
    1990             : 
    1991           8 :     SetLatch(&ProcGlobal->allProcs[procNumber].procLatch);
    1992           8 : }
    1993             : 
    1994             : /*
    1995             :  * BecomeLockGroupLeader - designate process as lock group leader
    1996             :  *
    1997             :  * Once this function has returned, other processes can join the lock group
    1998             :  * by calling BecomeLockGroupMember.
    1999             :  */
    2000             : void
    2001        1170 : BecomeLockGroupLeader(void)
    2002             : {
    2003             :     LWLock     *leader_lwlock;
    2004             : 
    2005             :     /* If we already did it, we don't need to do it again. */
    2006        1170 :     if (MyProc->lockGroupLeader == MyProc)
    2007        1032 :         return;
    2008             : 
    2009             :     /* We had better not be a follower. */
    2010             :     Assert(MyProc->lockGroupLeader == NULL);
    2011             : 
    2012             :     /* Create single-member group, containing only ourselves. */
    2013         138 :     leader_lwlock = LockHashPartitionLockByProc(MyProc);
    2014         138 :     LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
    2015         138 :     MyProc->lockGroupLeader = MyProc;
    2016         138 :     dlist_push_head(&MyProc->lockGroupMembers, &MyProc->lockGroupLink);
    2017         138 :     LWLockRelease(leader_lwlock);
    2018             : }
    2019             : 
    2020             : /*
    2021             :  * BecomeLockGroupMember - designate process as lock group member
    2022             :  *
    2023             :  * This is pretty straightforward except for the possibility that the leader
    2024             :  * whose group we're trying to join might exit before we manage to do so;
    2025             :  * and the PGPROC might get recycled for an unrelated process.  To avoid
    2026             :  * that, we require the caller to pass the PID of the intended PGPROC as
    2027             :  * an interlock.  Returns true if we successfully join the intended lock
    2028             :  * group, and false if not.
    2029             :  */
    2030             : bool
    2031        2734 : BecomeLockGroupMember(PGPROC *leader, int pid)
    2032             : {
    2033             :     LWLock     *leader_lwlock;
    2034        2734 :     bool        ok = false;
    2035             : 
    2036             :     /* Group leader can't become member of group */
    2037             :     Assert(MyProc != leader);
    2038             : 
    2039             :     /* Can't already be a member of a group */
    2040             :     Assert(MyProc->lockGroupLeader == NULL);
    2041             : 
    2042             :     /* PID must be valid. */
    2043             :     Assert(pid != 0);
    2044             : 
    2045             :     /*
    2046             :      * Get lock protecting the group fields.  Note LockHashPartitionLockByProc
    2047             :      * calculates the proc number based on the PGPROC slot without looking at
    2048             :      * its contents, so we will acquire the correct lock even if the leader
    2049             :      * PGPROC is in process of being recycled.
    2050             :      */
    2051        2734 :     leader_lwlock = LockHashPartitionLockByProc(leader);
    2052        2734 :     LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
    2053             : 
    2054             :     /* Is this the leader we're looking for? */
    2055        2734 :     if (leader->pid == pid && leader->lockGroupLeader == leader)
    2056             :     {
    2057             :         /* OK, join the group */
    2058        2734 :         ok = true;
    2059        2734 :         MyProc->lockGroupLeader = leader;
    2060        2734 :         dlist_push_tail(&leader->lockGroupMembers, &MyProc->lockGroupLink);
    2061             :     }
    2062        2734 :     LWLockRelease(leader_lwlock);
    2063             : 
    2064        2734 :     return ok;
    2065             : }

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