LCOV - code coverage report
Current view: top level - src/backend/storage/lmgr - proc.c (source / functions) Hit Total Coverage
Test: PostgreSQL 17devel Lines: 487 532 91.5 %
Date: 2023-12-05 08:11:01 Functions: 25 25 100.0 %
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) 1996-2023, 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             :  *      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/slot.h"
      43             : #include "replication/syncrep.h"
      44             : #include "replication/walsender.h"
      45             : #include "storage/condition_variable.h"
      46             : #include "storage/ipc.h"
      47             : #include "storage/lmgr.h"
      48             : #include "storage/pmsignal.h"
      49             : #include "storage/proc.h"
      50             : #include "storage/procarray.h"
      51             : #include "storage/procsignal.h"
      52             : #include "storage/spin.h"
      53             : #include "storage/standby.h"
      54             : #include "utils/timeout.h"
      55             : #include "utils/timestamp.h"
      56             : 
      57             : /* GUC variables */
      58             : int         DeadlockTimeout = 1000;
      59             : int         StatementTimeout = 0;
      60             : int         LockTimeout = 0;
      61             : int         IdleInTransactionSessionTimeout = 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             : /* If we are waiting for a lock, this points to the associated LOCALLOCK */
      83             : static LOCALLOCK *lockAwaited = NULL;
      84             : 
      85             : static DeadLockState deadlock_state = DS_NOT_YET_CHECKED;
      86             : 
      87             : /* Is a deadlock check pending? */
      88             : static volatile sig_atomic_t got_deadlock_timeout;
      89             : 
      90             : static void RemoveProcFromArray(int code, Datum arg);
      91             : static void ProcKill(int code, Datum arg);
      92             : static void AuxiliaryProcKill(int code, Datum arg);
      93             : static void CheckDeadLock(void);
      94             : 
      95             : 
      96             : /*
      97             :  * Report shared-memory space needed by InitProcGlobal.
      98             :  */
      99             : Size
     100        2934 : ProcGlobalShmemSize(void)
     101             : {
     102        2934 :     Size        size = 0;
     103             :     Size        TotalProcs =
     104        2934 :         add_size(MaxBackends, add_size(NUM_AUXILIARY_PROCS, max_prepared_xacts));
     105             : 
     106             :     /* ProcGlobal */
     107        2934 :     size = add_size(size, sizeof(PROC_HDR));
     108        2934 :     size = add_size(size, mul_size(TotalProcs, sizeof(PGPROC)));
     109        2934 :     size = add_size(size, sizeof(slock_t));
     110             : 
     111        2934 :     size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->xids)));
     112        2934 :     size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->subxidStates)));
     113        2934 :     size = add_size(size, mul_size(TotalProcs, sizeof(*ProcGlobal->statusFlags)));
     114             : 
     115        2934 :     return size;
     116             : }
     117             : 
     118             : /*
     119             :  * Report number of semaphores needed by InitProcGlobal.
     120             :  */
     121             : int
     122        2934 : ProcGlobalSemas(void)
     123             : {
     124             :     /*
     125             :      * We need a sema per backend (including autovacuum), plus one for each
     126             :      * auxiliary process.
     127             :      */
     128        2934 :     return MaxBackends + NUM_AUXILIARY_PROCS;
     129             : }
     130             : 
     131             : /*
     132             :  * InitProcGlobal -
     133             :  *    Initialize the global process table during postmaster or standalone
     134             :  *    backend startup.
     135             :  *
     136             :  *    We also create all the per-process semaphores we will need to support
     137             :  *    the requested number of backends.  We used to allocate semaphores
     138             :  *    only when backends were actually started up, but that is bad because
     139             :  *    it lets Postgres fail under load --- a lot of Unix systems are
     140             :  *    (mis)configured with small limits on the number of semaphores, and
     141             :  *    running out when trying to start another backend is a common failure.
     142             :  *    So, now we grab enough semaphores to support the desired max number
     143             :  *    of backends immediately at initialization --- if the sysadmin has set
     144             :  *    MaxConnections, max_worker_processes, max_wal_senders, or
     145             :  *    autovacuum_max_workers higher than his kernel will support, he'll
     146             :  *    find out sooner rather than later.
     147             :  *
     148             :  *    Another reason for creating semaphores here is that the semaphore
     149             :  *    implementation typically requires us to create semaphores in the
     150             :  *    postmaster, not in backends.
     151             :  *
     152             :  * Note: this is NOT called by individual backends under a postmaster,
     153             :  * not even in the EXEC_BACKEND case.  The ProcGlobal and AuxiliaryProcs
     154             :  * pointers must be propagated specially for EXEC_BACKEND operation.
     155             :  */
     156             : void
     157        1562 : InitProcGlobal(void)
     158             : {
     159             :     PGPROC     *procs;
     160             :     int         i,
     161             :                 j;
     162             :     bool        found;
     163        1562 :     uint32      TotalProcs = MaxBackends + NUM_AUXILIARY_PROCS + max_prepared_xacts;
     164             : 
     165             :     /* Create the ProcGlobal shared structure */
     166        1562 :     ProcGlobal = (PROC_HDR *)
     167        1562 :         ShmemInitStruct("Proc Header", sizeof(PROC_HDR), &found);
     168             :     Assert(!found);
     169             : 
     170             :     /*
     171             :      * Initialize the data structures.
     172             :      */
     173        1562 :     ProcGlobal->spins_per_delay = DEFAULT_SPINS_PER_DELAY;
     174        1562 :     dlist_init(&ProcGlobal->freeProcs);
     175        1562 :     dlist_init(&ProcGlobal->autovacFreeProcs);
     176        1562 :     dlist_init(&ProcGlobal->bgworkerFreeProcs);
     177        1562 :     dlist_init(&ProcGlobal->walsenderFreeProcs);
     178        1562 :     ProcGlobal->startupBufferPinWaitBufId = -1;
     179        1562 :     ProcGlobal->walwriterLatch = NULL;
     180        1562 :     ProcGlobal->checkpointerLatch = NULL;
     181        1562 :     pg_atomic_init_u32(&ProcGlobal->procArrayGroupFirst, INVALID_PGPROCNO);
     182        1562 :     pg_atomic_init_u32(&ProcGlobal->clogGroupFirst, INVALID_PGPROCNO);
     183             : 
     184             :     /*
     185             :      * Create and initialize all the PGPROC structures we'll need.  There are
     186             :      * five separate consumers: (1) normal backends, (2) autovacuum workers
     187             :      * and the autovacuum launcher, (3) background workers, (4) auxiliary
     188             :      * processes, and (5) prepared transactions.  Each PGPROC structure is
     189             :      * dedicated to exactly one of these purposes, and they do not move
     190             :      * between groups.
     191             :      */
     192        1562 :     procs = (PGPROC *) ShmemAlloc(TotalProcs * sizeof(PGPROC));
     193        1562 :     MemSet(procs, 0, TotalProcs * sizeof(PGPROC));
     194        1562 :     ProcGlobal->allProcs = procs;
     195             :     /* XXX allProcCount isn't really all of them; it excludes prepared xacts */
     196        1562 :     ProcGlobal->allProcCount = MaxBackends + NUM_AUXILIARY_PROCS;
     197             : 
     198             :     /*
     199             :      * Allocate arrays mirroring PGPROC fields in a dense manner. See
     200             :      * PROC_HDR.
     201             :      *
     202             :      * XXX: It might make sense to increase padding for these arrays, given
     203             :      * how hotly they are accessed.
     204             :      */
     205        3124 :     ProcGlobal->xids =
     206        1562 :         (TransactionId *) ShmemAlloc(TotalProcs * sizeof(*ProcGlobal->xids));
     207        6602 :     MemSet(ProcGlobal->xids, 0, TotalProcs * sizeof(*ProcGlobal->xids));
     208        1562 :     ProcGlobal->subxidStates = (XidCacheStatus *) ShmemAlloc(TotalProcs * sizeof(*ProcGlobal->subxidStates));
     209        1772 :     MemSet(ProcGlobal->subxidStates, 0, TotalProcs * sizeof(*ProcGlobal->subxidStates));
     210        1562 :     ProcGlobal->statusFlags = (uint8 *) ShmemAlloc(TotalProcs * sizeof(*ProcGlobal->statusFlags));
     211        1634 :     MemSet(ProcGlobal->statusFlags, 0, TotalProcs * sizeof(*ProcGlobal->statusFlags));
     212             : 
     213      141144 :     for (i = 0; i < TotalProcs; i++)
     214             :     {
     215      139582 :         PGPROC     *proc = &procs[i];
     216             : 
     217             :         /* Common initialization for all PGPROCs, regardless of type. */
     218             : 
     219             :         /*
     220             :          * Set up per-PGPROC semaphore, latch, and fpInfoLock.  Prepared xact
     221             :          * dummy PGPROCs don't need these though - they're never associated
     222             :          * with a real process
     223             :          */
     224      139582 :         if (i < MaxBackends + NUM_AUXILIARY_PROCS)
     225             :         {
     226      138040 :             proc->sem = PGSemaphoreCreate();
     227      138040 :             InitSharedLatch(&(proc->procLatch));
     228      138040 :             LWLockInitialize(&(proc->fpInfoLock), LWTRANCHE_LOCK_FASTPATH);
     229             :         }
     230      139582 :         proc->pgprocno = i;
     231             : 
     232             :         /*
     233             :          * Newly created PGPROCs for normal backends, autovacuum and bgworkers
     234             :          * must be queued up on the appropriate free list.  Because there can
     235             :          * only ever be a small, fixed number of auxiliary processes, no free
     236             :          * list is used in that case; InitAuxiliaryProcess() instead uses a
     237             :          * linear search.   PGPROCs for prepared transactions are added to a
     238             :          * free list by TwoPhaseShmemInit().
     239             :          */
     240      139582 :         if (i < MaxConnections)
     241             :         {
     242             :             /* PGPROC for normal backend, add to freeProcs list */
     243      101180 :             dlist_push_head(&ProcGlobal->freeProcs, &proc->links);
     244      101180 :             proc->procgloballist = &ProcGlobal->freeProcs;
     245             :         }
     246       38402 :         else if (i < MaxConnections + autovacuum_max_workers + 1)
     247             :         {
     248             :             /* PGPROC for AV launcher/worker, add to autovacFreeProcs list */
     249        6248 :             dlist_push_head(&ProcGlobal->autovacFreeProcs, &proc->links);
     250        6248 :             proc->procgloballist = &ProcGlobal->autovacFreeProcs;
     251             :         }
     252       32154 :         else if (i < MaxConnections + autovacuum_max_workers + 1 + max_worker_processes)
     253             :         {
     254             :             /* PGPROC for bgworker, add to bgworkerFreeProcs list */
     255       12544 :             dlist_push_head(&ProcGlobal->bgworkerFreeProcs, &proc->links);
     256       12544 :             proc->procgloballist = &ProcGlobal->bgworkerFreeProcs;
     257             :         }
     258       19610 :         else if (i < MaxBackends)
     259             :         {
     260             :             /* PGPROC for walsender, add to walsenderFreeProcs list */
     261       10258 :             dlist_push_head(&ProcGlobal->walsenderFreeProcs, &proc->links);
     262       10258 :             proc->procgloballist = &ProcGlobal->walsenderFreeProcs;
     263             :         }
     264             : 
     265             :         /* Initialize myProcLocks[] shared memory queues. */
     266     2372894 :         for (j = 0; j < NUM_LOCK_PARTITIONS; j++)
     267     2233312 :             dlist_init(&(proc->myProcLocks[j]));
     268             : 
     269             :         /* Initialize lockGroupMembers list. */
     270      139582 :         dlist_init(&proc->lockGroupMembers);
     271             : 
     272             :         /*
     273             :          * Initialize the atomic variables, otherwise, it won't be safe to
     274             :          * access them for backends that aren't currently in use.
     275             :          */
     276      139582 :         pg_atomic_init_u32(&(proc->procArrayGroupNext), INVALID_PGPROCNO);
     277      139582 :         pg_atomic_init_u32(&(proc->clogGroupNext), INVALID_PGPROCNO);
     278      139582 :         pg_atomic_init_u64(&(proc->waitStart), 0);
     279             :     }
     280             : 
     281             :     /*
     282             :      * Save pointers to the blocks of PGPROC structures reserved for auxiliary
     283             :      * processes and prepared transactions.
     284             :      */
     285        1562 :     AuxiliaryProcs = &procs[MaxBackends];
     286        1562 :     PreparedXactProcs = &procs[MaxBackends + NUM_AUXILIARY_PROCS];
     287             : 
     288             :     /* Create ProcStructLock spinlock, too */
     289        1562 :     ProcStructLock = (slock_t *) ShmemAlloc(sizeof(slock_t));
     290        1562 :     SpinLockInit(ProcStructLock);
     291        1562 : }
     292             : 
     293             : /*
     294             :  * InitProcess -- initialize a per-process PGPROC entry for this backend
     295             :  */
     296             : void
     297       24096 : InitProcess(void)
     298             : {
     299             :     dlist_head *procgloballist;
     300             : 
     301             :     /*
     302             :      * ProcGlobal should be set up already (if we are a backend, we inherit
     303             :      * this by fork() or EXEC_BACKEND mechanism from the postmaster).
     304             :      */
     305       24096 :     if (ProcGlobal == NULL)
     306           0 :         elog(PANIC, "proc header uninitialized");
     307             : 
     308       24096 :     if (MyProc != NULL)
     309           0 :         elog(ERROR, "you already exist");
     310             : 
     311             :     /* Decide which list should supply our PGPROC. */
     312       24096 :     if (IsAnyAutoVacuumProcess())
     313         634 :         procgloballist = &ProcGlobal->autovacFreeProcs;
     314       23462 :     else if (IsBackgroundWorker)
     315        3944 :         procgloballist = &ProcGlobal->bgworkerFreeProcs;
     316       19518 :     else if (am_walsender)
     317        1716 :         procgloballist = &ProcGlobal->walsenderFreeProcs;
     318             :     else
     319       17802 :         procgloballist = &ProcGlobal->freeProcs;
     320             : 
     321             :     /*
     322             :      * Try to get a proc struct from the appropriate free list.  If this
     323             :      * fails, we must be out of PGPROC structures (not to mention semaphores).
     324             :      *
     325             :      * While we are holding the ProcStructLock, also copy the current shared
     326             :      * estimate of spins_per_delay to local storage.
     327             :      */
     328       24096 :     SpinLockAcquire(ProcStructLock);
     329             : 
     330       24096 :     set_spins_per_delay(ProcGlobal->spins_per_delay);
     331             : 
     332       24096 :     if (!dlist_is_empty(procgloballist))
     333             :     {
     334       24092 :         MyProc = (PGPROC *) dlist_pop_head_node(procgloballist);
     335       24092 :         SpinLockRelease(ProcStructLock);
     336             :     }
     337             :     else
     338             :     {
     339             :         /*
     340             :          * If we reach here, all the PGPROCs are in use.  This is one of the
     341             :          * possible places to detect "too many backends", so give the standard
     342             :          * error message.  XXX do we need to give a different failure message
     343             :          * in the autovacuum case?
     344             :          */
     345           4 :         SpinLockRelease(ProcStructLock);
     346           4 :         if (am_walsender)
     347           4 :             ereport(FATAL,
     348             :                     (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
     349             :                      errmsg("number of requested standby connections exceeds max_wal_senders (currently %d)",
     350             :                             max_wal_senders)));
     351           0 :         ereport(FATAL,
     352             :                 (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
     353             :                  errmsg("sorry, too many clients already")));
     354             :     }
     355             : 
     356             :     /*
     357             :      * Cross-check that the PGPROC is of the type we expect; if this were not
     358             :      * the case, it would get returned to the wrong list.
     359             :      */
     360             :     Assert(MyProc->procgloballist == procgloballist);
     361             : 
     362             :     /*
     363             :      * Now that we have a PGPROC, mark ourselves as an active postmaster
     364             :      * child; this is so that the postmaster can detect it if we exit without
     365             :      * cleaning up.  (XXX autovac launcher currently doesn't participate in
     366             :      * this; it probably should.)
     367             :      */
     368       24092 :     if (IsUnderPostmaster && !IsAutoVacuumLauncherProcess())
     369       23332 :         MarkPostmasterChildActive();
     370             : 
     371             :     /*
     372             :      * Initialize all fields of MyProc, except for those previously
     373             :      * initialized by InitProcGlobal.
     374             :      */
     375       24092 :     dlist_node_init(&MyProc->links);
     376       24092 :     MyProc->waitStatus = PROC_WAIT_STATUS_OK;
     377       24092 :     MyProc->lxid = InvalidLocalTransactionId;
     378       24092 :     MyProc->fpVXIDLock = false;
     379       24092 :     MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
     380       24092 :     MyProc->xid = InvalidTransactionId;
     381       24092 :     MyProc->xmin = InvalidTransactionId;
     382       24092 :     MyProc->pid = MyProcPid;
     383             :     /* backendId, databaseId and roleId will be filled in later */
     384       24092 :     MyProc->backendId = InvalidBackendId;
     385       24092 :     MyProc->databaseId = InvalidOid;
     386       24092 :     MyProc->roleId = InvalidOid;
     387       24092 :     MyProc->tempNamespaceId = InvalidOid;
     388       24092 :     MyProc->isBackgroundWorker = IsBackgroundWorker;
     389       24092 :     MyProc->delayChkptFlags = 0;
     390       24092 :     MyProc->statusFlags = 0;
     391             :     /* NB -- autovac launcher intentionally does not set IS_AUTOVACUUM */
     392       24092 :     if (IsAutoVacuumWorkerProcess())
     393          20 :         MyProc->statusFlags |= PROC_IS_AUTOVACUUM;
     394       24092 :     MyProc->lwWaiting = LW_WS_NOT_WAITING;
     395       24092 :     MyProc->lwWaitMode = 0;
     396       24092 :     MyProc->waitLock = NULL;
     397       24092 :     MyProc->waitProcLock = NULL;
     398       24092 :     pg_atomic_write_u64(&MyProc->waitStart, 0);
     399             : #ifdef USE_ASSERT_CHECKING
     400             :     {
     401             :         int         i;
     402             : 
     403             :         /* Last process should have released all locks. */
     404             :         for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
     405             :             Assert(dlist_is_empty(&(MyProc->myProcLocks[i])));
     406             :     }
     407             : #endif
     408       24092 :     MyProc->recoveryConflictPending = false;
     409             : 
     410             :     /* Initialize fields for sync rep */
     411       24092 :     MyProc->waitLSN = 0;
     412       24092 :     MyProc->syncRepState = SYNC_REP_NOT_WAITING;
     413       24092 :     dlist_node_init(&MyProc->syncRepLinks);
     414             : 
     415             :     /* Initialize fields for group XID clearing. */
     416       24092 :     MyProc->procArrayGroupMember = false;
     417       24092 :     MyProc->procArrayGroupMemberXid = InvalidTransactionId;
     418             :     Assert(pg_atomic_read_u32(&MyProc->procArrayGroupNext) == INVALID_PGPROCNO);
     419             : 
     420             :     /* Check that group locking fields are in a proper initial state. */
     421             :     Assert(MyProc->lockGroupLeader == NULL);
     422             :     Assert(dlist_is_empty(&MyProc->lockGroupMembers));
     423             : 
     424             :     /* Initialize wait event information. */
     425       24092 :     MyProc->wait_event_info = 0;
     426             : 
     427             :     /* Initialize fields for group transaction status update. */
     428       24092 :     MyProc->clogGroupMember = false;
     429       24092 :     MyProc->clogGroupMemberXid = InvalidTransactionId;
     430       24092 :     MyProc->clogGroupMemberXidStatus = TRANSACTION_STATUS_IN_PROGRESS;
     431       24092 :     MyProc->clogGroupMemberPage = -1;
     432       24092 :     MyProc->clogGroupMemberLsn = InvalidXLogRecPtr;
     433             :     Assert(pg_atomic_read_u32(&MyProc->clogGroupNext) == INVALID_PGPROCNO);
     434             : 
     435             :     /*
     436             :      * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
     437             :      * on it.  That allows us to repoint the process latch, which so far
     438             :      * points to process local one, to the shared one.
     439             :      */
     440       24092 :     OwnLatch(&MyProc->procLatch);
     441       24092 :     SwitchToSharedLatch();
     442             : 
     443             :     /* now that we have a proc, report wait events to shared memory */
     444       24092 :     pgstat_set_wait_event_storage(&MyProc->wait_event_info);
     445             : 
     446             :     /*
     447             :      * We might be reusing a semaphore that belonged to a failed process. So
     448             :      * be careful and reinitialize its value here.  (This is not strictly
     449             :      * necessary anymore, but seems like a good idea for cleanliness.)
     450             :      */
     451       24092 :     PGSemaphoreReset(MyProc->sem);
     452             : 
     453             :     /*
     454             :      * Arrange to clean up at backend exit.
     455             :      */
     456       24092 :     on_shmem_exit(ProcKill, 0);
     457             : 
     458             :     /*
     459             :      * Now that we have a PGPROC, we could try to acquire locks, so initialize
     460             :      * local state needed for LWLocks, and the deadlock checker.
     461             :      */
     462       24092 :     InitLWLockAccess();
     463       24092 :     InitDeadLockChecking();
     464             : 
     465             : #ifdef EXEC_BACKEND
     466             : 
     467             :     /*
     468             :      * Initialize backend-local pointers to all the shared data structures.
     469             :      * (We couldn't do this until now because it needs LWLocks.)
     470             :      */
     471             :     if (IsUnderPostmaster)
     472             :         AttachSharedMemoryStructs();
     473             : #endif
     474       24092 : }
     475             : 
     476             : /*
     477             :  * InitProcessPhase2 -- make MyProc visible in the shared ProcArray.
     478             :  *
     479             :  * This is separate from InitProcess because we can't acquire LWLocks until
     480             :  * we've created a PGPROC, but in the EXEC_BACKEND case ProcArrayAdd won't
     481             :  * work until after we've done AttachSharedMemoryStructs.
     482             :  */
     483             : void
     484       24074 : InitProcessPhase2(void)
     485             : {
     486             :     Assert(MyProc != NULL);
     487             : 
     488             :     /*
     489             :      * Add our PGPROC to the PGPROC array in shared memory.
     490             :      */
     491       24074 :     ProcArrayAdd(MyProc);
     492             : 
     493             :     /*
     494             :      * Arrange to clean that up at backend exit.
     495             :      */
     496       24074 :     on_shmem_exit(RemoveProcFromArray, 0);
     497       24074 : }
     498             : 
     499             : /*
     500             :  * InitAuxiliaryProcess -- create a PGPROC entry for an auxiliary process
     501             :  *
     502             :  * This is called by bgwriter and similar processes so that they will have a
     503             :  * MyProc value that's real enough to let them wait for LWLocks.  The PGPROC
     504             :  * and sema that are assigned are one of the extra ones created during
     505             :  * InitProcGlobal.
     506             :  *
     507             :  * Auxiliary processes are presently not expected to wait for real (lockmgr)
     508             :  * locks, so we need not set up the deadlock checker.  They are never added
     509             :  * to the ProcArray or the sinval messaging mechanism, either.  They also
     510             :  * don't get a VXID assigned, since this is only useful when we actually
     511             :  * hold lockmgr locks.
     512             :  *
     513             :  * Startup process however uses locks but never waits for them in the
     514             :  * normal backend sense. Startup process also takes part in sinval messaging
     515             :  * as a sendOnly process, so never reads messages from sinval queue. So
     516             :  * Startup process does have a VXID and does show up in pg_locks.
     517             :  */
     518             : void
     519        3718 : InitAuxiliaryProcess(void)
     520             : {
     521             :     PGPROC     *auxproc;
     522             :     int         proctype;
     523             : 
     524             :     /*
     525             :      * ProcGlobal should be set up already (if we are a backend, we inherit
     526             :      * this by fork() or EXEC_BACKEND mechanism from the postmaster).
     527             :      */
     528        3718 :     if (ProcGlobal == NULL || AuxiliaryProcs == NULL)
     529           0 :         elog(PANIC, "proc header uninitialized");
     530             : 
     531        3718 :     if (MyProc != NULL)
     532           0 :         elog(ERROR, "you already exist");
     533             : 
     534             :     /*
     535             :      * We use the ProcStructLock to protect assignment and releasing of
     536             :      * AuxiliaryProcs entries.
     537             :      *
     538             :      * While we are holding the ProcStructLock, also copy the current shared
     539             :      * estimate of spins_per_delay to local storage.
     540             :      */
     541        3718 :     SpinLockAcquire(ProcStructLock);
     542             : 
     543        3718 :     set_spins_per_delay(ProcGlobal->spins_per_delay);
     544             : 
     545             :     /*
     546             :      * Find a free auxproc ... *big* trouble if there isn't one ...
     547             :      */
     548        9268 :     for (proctype = 0; proctype < NUM_AUXILIARY_PROCS; proctype++)
     549             :     {
     550        9268 :         auxproc = &AuxiliaryProcs[proctype];
     551        9268 :         if (auxproc->pid == 0)
     552        3718 :             break;
     553             :     }
     554        3718 :     if (proctype >= NUM_AUXILIARY_PROCS)
     555             :     {
     556           0 :         SpinLockRelease(ProcStructLock);
     557           0 :         elog(FATAL, "all AuxiliaryProcs are in use");
     558             :     }
     559             : 
     560             :     /* Mark auxiliary proc as in use by me */
     561             :     /* use volatile pointer to prevent code rearrangement */
     562        3718 :     ((volatile PGPROC *) auxproc)->pid = MyProcPid;
     563             : 
     564        3718 :     MyProc = auxproc;
     565             : 
     566        3718 :     SpinLockRelease(ProcStructLock);
     567             : 
     568             :     /*
     569             :      * Initialize all fields of MyProc, except for those previously
     570             :      * initialized by InitProcGlobal.
     571             :      */
     572        3718 :     dlist_node_init(&MyProc->links);
     573        3718 :     MyProc->waitStatus = PROC_WAIT_STATUS_OK;
     574        3718 :     MyProc->lxid = InvalidLocalTransactionId;
     575        3718 :     MyProc->fpVXIDLock = false;
     576        3718 :     MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
     577        3718 :     MyProc->xid = InvalidTransactionId;
     578        3718 :     MyProc->xmin = InvalidTransactionId;
     579        3718 :     MyProc->backendId = InvalidBackendId;
     580        3718 :     MyProc->databaseId = InvalidOid;
     581        3718 :     MyProc->roleId = InvalidOid;
     582        3718 :     MyProc->tempNamespaceId = InvalidOid;
     583        3718 :     MyProc->isBackgroundWorker = IsBackgroundWorker;
     584        3718 :     MyProc->delayChkptFlags = 0;
     585        3718 :     MyProc->statusFlags = 0;
     586        3718 :     MyProc->lwWaiting = LW_WS_NOT_WAITING;
     587        3718 :     MyProc->lwWaitMode = 0;
     588        3718 :     MyProc->waitLock = NULL;
     589        3718 :     MyProc->waitProcLock = NULL;
     590        3718 :     pg_atomic_write_u64(&MyProc->waitStart, 0);
     591             : #ifdef USE_ASSERT_CHECKING
     592             :     {
     593             :         int         i;
     594             : 
     595             :         /* Last process should have released all locks. */
     596             :         for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
     597             :             Assert(dlist_is_empty(&(MyProc->myProcLocks[i])));
     598             :     }
     599             : #endif
     600             : 
     601             :     /*
     602             :      * Acquire ownership of the PGPROC's latch, so that we can use WaitLatch
     603             :      * on it.  That allows us to repoint the process latch, which so far
     604             :      * points to process local one, to the shared one.
     605             :      */
     606        3718 :     OwnLatch(&MyProc->procLatch);
     607        3718 :     SwitchToSharedLatch();
     608             : 
     609             :     /* now that we have a proc, report wait events to shared memory */
     610        3718 :     pgstat_set_wait_event_storage(&MyProc->wait_event_info);
     611             : 
     612             :     /* Check that group locking fields are in a proper initial state. */
     613             :     Assert(MyProc->lockGroupLeader == NULL);
     614             :     Assert(dlist_is_empty(&MyProc->lockGroupMembers));
     615             : 
     616             :     /*
     617             :      * We might be reusing a semaphore that belonged to a failed process. So
     618             :      * be careful and reinitialize its value here.  (This is not strictly
     619             :      * necessary anymore, but seems like a good idea for cleanliness.)
     620             :      */
     621        3718 :     PGSemaphoreReset(MyProc->sem);
     622             : 
     623             :     /*
     624             :      * Arrange to clean up at process exit.
     625             :      */
     626        3718 :     on_shmem_exit(AuxiliaryProcKill, Int32GetDatum(proctype));
     627             : 
     628             :     /*
     629             :      * Now that we have a PGPROC, we could try to acquire lightweight locks.
     630             :      * Initialize local state needed for them.  (Heavyweight locks cannot be
     631             :      * acquired in aux processes.)
     632             :      */
     633        3718 :     InitLWLockAccess();
     634             : 
     635             : #ifdef EXEC_BACKEND
     636             : 
     637             :     /*
     638             :      * Initialize backend-local pointers to all the shared data structures.
     639             :      * (We couldn't do this until now because it needs LWLocks.)
     640             :      */
     641             :     if (IsUnderPostmaster)
     642             :         AttachSharedMemoryStructs();
     643             : #endif
     644        3718 : }
     645             : 
     646             : /*
     647             :  * Used from bufmgr to share the value of the buffer that Startup waits on,
     648             :  * or to reset the value to "not waiting" (-1). This allows processing
     649             :  * of recovery conflicts for buffer pins. Set is made before backends look
     650             :  * at this value, so locking not required, especially since the set is
     651             :  * an atomic integer set operation.
     652             :  */
     653             : void
     654          44 : SetStartupBufferPinWaitBufId(int bufid)
     655             : {
     656             :     /* use volatile pointer to prevent code rearrangement */
     657          44 :     volatile PROC_HDR *procglobal = ProcGlobal;
     658             : 
     659          44 :     procglobal->startupBufferPinWaitBufId = bufid;
     660          44 : }
     661             : 
     662             : /*
     663             :  * Used by backends when they receive a request to check for buffer pin waits.
     664             :  */
     665             : int
     666          10 : GetStartupBufferPinWaitBufId(void)
     667             : {
     668             :     /* use volatile pointer to prevent code rearrangement */
     669          10 :     volatile PROC_HDR *procglobal = ProcGlobal;
     670             : 
     671          10 :     return procglobal->startupBufferPinWaitBufId;
     672             : }
     673             : 
     674             : /*
     675             :  * Check whether there are at least N free PGPROC objects.  If false is
     676             :  * returned, *nfree will be set to the number of free PGPROC objects.
     677             :  * Otherwise, *nfree will be set to n.
     678             :  *
     679             :  * Note: this is designed on the assumption that N will generally be small.
     680             :  */
     681             : bool
     682         406 : HaveNFreeProcs(int n, int *nfree)
     683             : {
     684             :     dlist_iter  iter;
     685             : 
     686             :     Assert(n > 0);
     687             :     Assert(nfree);
     688             : 
     689         406 :     SpinLockAcquire(ProcStructLock);
     690             : 
     691         406 :     *nfree = 0;
     692        1218 :     dlist_foreach(iter, &ProcGlobal->freeProcs)
     693             :     {
     694        1218 :         (*nfree)++;
     695        1218 :         if (*nfree == n)
     696         406 :             break;
     697             :     }
     698             : 
     699         406 :     SpinLockRelease(ProcStructLock);
     700             : 
     701         406 :     return (*nfree == n);
     702             : }
     703             : 
     704             : /*
     705             :  * Check if the current process is awaiting a lock.
     706             :  */
     707             : bool
     708          16 : IsWaitingForLock(void)
     709             : {
     710          16 :     if (lockAwaited == NULL)
     711          12 :         return false;
     712             : 
     713           4 :     return true;
     714             : }
     715             : 
     716             : /*
     717             :  * Cancel any pending wait for lock, when aborting a transaction, and revert
     718             :  * any strong lock count acquisition for a lock being acquired.
     719             :  *
     720             :  * (Normally, this would only happen if we accept a cancel/die
     721             :  * interrupt while waiting; but an ereport(ERROR) before or during the lock
     722             :  * wait is within the realm of possibility, too.)
     723             :  */
     724             : void
     725      565550 : LockErrorCleanup(void)
     726             : {
     727             :     LWLock     *partitionLock;
     728             :     DisableTimeoutParams timeouts[2];
     729             : 
     730      565550 :     HOLD_INTERRUPTS();
     731             : 
     732      565550 :     AbortStrongLockAcquire();
     733             : 
     734             :     /* Nothing to do if we weren't waiting for a lock */
     735      565550 :     if (lockAwaited == NULL)
     736             :     {
     737      565466 :         RESUME_INTERRUPTS();
     738      565466 :         return;
     739             :     }
     740             : 
     741             :     /*
     742             :      * Turn off the deadlock and lock timeout timers, if they are still
     743             :      * running (see ProcSleep).  Note we must preserve the LOCK_TIMEOUT
     744             :      * indicator flag, since this function is executed before
     745             :      * ProcessInterrupts when responding to SIGINT; else we'd lose the
     746             :      * knowledge that the SIGINT came from a lock timeout and not an external
     747             :      * source.
     748             :      */
     749          84 :     timeouts[0].id = DEADLOCK_TIMEOUT;
     750          84 :     timeouts[0].keep_indicator = false;
     751          84 :     timeouts[1].id = LOCK_TIMEOUT;
     752          84 :     timeouts[1].keep_indicator = true;
     753          84 :     disable_timeouts(timeouts, 2);
     754             : 
     755             :     /* Unlink myself from the wait queue, if on it (might not be anymore!) */
     756          84 :     partitionLock = LockHashPartitionLock(lockAwaited->hashcode);
     757          84 :     LWLockAcquire(partitionLock, LW_EXCLUSIVE);
     758             : 
     759          84 :     if (!dlist_node_is_detached(&MyProc->links))
     760             :     {
     761             :         /* We could not have been granted the lock yet */
     762          82 :         RemoveFromWaitQueue(MyProc, lockAwaited->hashcode);
     763             :     }
     764             :     else
     765             :     {
     766             :         /*
     767             :          * Somebody kicked us off the lock queue already.  Perhaps they
     768             :          * granted us the lock, or perhaps they detected a deadlock. If they
     769             :          * did grant us the lock, we'd better remember it in our local lock
     770             :          * table.
     771             :          */
     772           2 :         if (MyProc->waitStatus == PROC_WAIT_STATUS_OK)
     773           2 :             GrantAwaitedLock();
     774             :     }
     775             : 
     776          84 :     lockAwaited = NULL;
     777             : 
     778          84 :     LWLockRelease(partitionLock);
     779             : 
     780          84 :     RESUME_INTERRUPTS();
     781             : }
     782             : 
     783             : 
     784             : /*
     785             :  * ProcReleaseLocks() -- release locks associated with current transaction
     786             :  *          at main transaction commit or abort
     787             :  *
     788             :  * At main transaction commit, we release standard locks except session locks.
     789             :  * At main transaction abort, we release all locks including session locks.
     790             :  *
     791             :  * Advisory locks are released only if they are transaction-level;
     792             :  * session-level holds remain, whether this is a commit or not.
     793             :  *
     794             :  * At subtransaction commit, we don't release any locks (so this func is not
     795             :  * needed at all); we will defer the releasing to the parent transaction.
     796             :  * At subtransaction abort, we release all locks held by the subtransaction;
     797             :  * this is implemented by retail releasing of the locks under control of
     798             :  * the ResourceOwner mechanism.
     799             :  */
     800             : void
     801      514172 : ProcReleaseLocks(bool isCommit)
     802             : {
     803      514172 :     if (!MyProc)
     804           0 :         return;
     805             :     /* If waiting, get off wait queue (should only be needed after error) */
     806      514172 :     LockErrorCleanup();
     807             :     /* Release standard locks, including session-level if aborting */
     808      514172 :     LockReleaseAll(DEFAULT_LOCKMETHOD, !isCommit);
     809             :     /* Release transaction-level advisory locks */
     810      514172 :     LockReleaseAll(USER_LOCKMETHOD, false);
     811             : }
     812             : 
     813             : 
     814             : /*
     815             :  * RemoveProcFromArray() -- Remove this process from the shared ProcArray.
     816             :  */
     817             : static void
     818       24074 : RemoveProcFromArray(int code, Datum arg)
     819             : {
     820             :     Assert(MyProc != NULL);
     821       24074 :     ProcArrayRemove(MyProc, InvalidTransactionId);
     822       24074 : }
     823             : 
     824             : /*
     825             :  * ProcKill() -- Destroy the per-proc data structure for
     826             :  *      this process. Release any of its held LW locks.
     827             :  */
     828             : static void
     829       24092 : ProcKill(int code, Datum arg)
     830             : {
     831             :     PGPROC     *proc;
     832             :     dlist_head *procgloballist;
     833             : 
     834             :     Assert(MyProc != NULL);
     835             : 
     836             :     /* not safe if forked by system(), etc. */
     837       24092 :     if (MyProc->pid != (int) getpid())
     838           0 :         elog(PANIC, "ProcKill() called in child process");
     839             : 
     840             :     /* Make sure we're out of the sync rep lists */
     841       24092 :     SyncRepCleanupAtProcExit();
     842             : 
     843             : #ifdef USE_ASSERT_CHECKING
     844             :     {
     845             :         int         i;
     846             : 
     847             :         /* Last process should have released all locks. */
     848             :         for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
     849             :             Assert(dlist_is_empty(&(MyProc->myProcLocks[i])));
     850             :     }
     851             : #endif
     852             : 
     853             :     /*
     854             :      * Release any LW locks I am holding.  There really shouldn't be any, but
     855             :      * it's cheap to check again before we cut the knees off the LWLock
     856             :      * facility by releasing our PGPROC ...
     857             :      */
     858       24092 :     LWLockReleaseAll();
     859             : 
     860             :     /* Cancel any pending condition variable sleep, too */
     861       24092 :     ConditionVariableCancelSleep();
     862             : 
     863             :     /*
     864             :      * Detach from any lock group of which we are a member.  If the leader
     865             :      * exits before all other group members, its PGPROC will remain allocated
     866             :      * until the last group process exits; that process must return the
     867             :      * leader's PGPROC to the appropriate list.
     868             :      */
     869       24092 :     if (MyProc->lockGroupLeader != NULL)
     870             :     {
     871        2700 :         PGPROC     *leader = MyProc->lockGroupLeader;
     872        2700 :         LWLock     *leader_lwlock = LockHashPartitionLockByProc(leader);
     873             : 
     874        2700 :         LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
     875             :         Assert(!dlist_is_empty(&leader->lockGroupMembers));
     876        2700 :         dlist_delete(&MyProc->lockGroupLink);
     877        2700 :         if (dlist_is_empty(&leader->lockGroupMembers))
     878             :         {
     879         108 :             leader->lockGroupLeader = NULL;
     880         108 :             if (leader != MyProc)
     881             :             {
     882           0 :                 procgloballist = leader->procgloballist;
     883             : 
     884             :                 /* Leader exited first; return its PGPROC. */
     885           0 :                 SpinLockAcquire(ProcStructLock);
     886           0 :                 dlist_push_head(procgloballist, &leader->links);
     887           0 :                 SpinLockRelease(ProcStructLock);
     888             :             }
     889             :         }
     890        2592 :         else if (leader != MyProc)
     891        2592 :             MyProc->lockGroupLeader = NULL;
     892        2700 :         LWLockRelease(leader_lwlock);
     893             :     }
     894             : 
     895             :     /*
     896             :      * Reset MyLatch to the process local one.  This is so that signal
     897             :      * handlers et al can continue using the latch after the shared latch
     898             :      * isn't ours anymore.
     899             :      *
     900             :      * Similarly, stop reporting wait events to MyProc->wait_event_info.
     901             :      *
     902             :      * After that clear MyProc and disown the shared latch.
     903             :      */
     904       24092 :     SwitchBackToLocalLatch();
     905       24092 :     pgstat_reset_wait_event_storage();
     906             : 
     907       24092 :     proc = MyProc;
     908       24092 :     MyProc = NULL;
     909       24092 :     DisownLatch(&proc->procLatch);
     910             : 
     911       24092 :     procgloballist = proc->procgloballist;
     912       24092 :     SpinLockAcquire(ProcStructLock);
     913             : 
     914             :     /*
     915             :      * If we're still a member of a locking group, that means we're a leader
     916             :      * which has somehow exited before its children.  The last remaining child
     917             :      * will release our PGPROC.  Otherwise, release it now.
     918             :      */
     919       24092 :     if (proc->lockGroupLeader == NULL)
     920             :     {
     921             :         /* Since lockGroupLeader is NULL, lockGroupMembers should be empty. */
     922             :         Assert(dlist_is_empty(&proc->lockGroupMembers));
     923             : 
     924             :         /* Return PGPROC structure (and semaphore) to appropriate freelist */
     925       24092 :         dlist_push_tail(procgloballist, &proc->links);
     926             :     }
     927             : 
     928             :     /* Update shared estimate of spins_per_delay */
     929       24092 :     ProcGlobal->spins_per_delay = update_spins_per_delay(ProcGlobal->spins_per_delay);
     930             : 
     931       24092 :     SpinLockRelease(ProcStructLock);
     932             : 
     933             :     /*
     934             :      * This process is no longer present in shared memory in any meaningful
     935             :      * way, so tell the postmaster we've cleaned up acceptably well. (XXX
     936             :      * autovac launcher should be included here someday)
     937             :      */
     938       24092 :     if (IsUnderPostmaster && !IsAutoVacuumLauncherProcess())
     939       23332 :         MarkPostmasterChildInactive();
     940             : 
     941             :     /* wake autovac launcher if needed -- see comments in FreeWorkerInfo */
     942       24092 :     if (AutovacuumLauncherPid != 0)
     943          20 :         kill(AutovacuumLauncherPid, SIGUSR2);
     944       24092 : }
     945             : 
     946             : /*
     947             :  * AuxiliaryProcKill() -- Cut-down version of ProcKill for auxiliary
     948             :  *      processes (bgwriter, etc).  The PGPROC and sema are not released, only
     949             :  *      marked as not-in-use.
     950             :  */
     951             : static void
     952        3718 : AuxiliaryProcKill(int code, Datum arg)
     953             : {
     954        3718 :     int         proctype = DatumGetInt32(arg);
     955             :     PGPROC     *auxproc PG_USED_FOR_ASSERTS_ONLY;
     956             :     PGPROC     *proc;
     957             : 
     958             :     Assert(proctype >= 0 && proctype < NUM_AUXILIARY_PROCS);
     959             : 
     960             :     /* not safe if forked by system(), etc. */
     961        3718 :     if (MyProc->pid != (int) getpid())
     962           0 :         elog(PANIC, "AuxiliaryProcKill() called in child process");
     963             : 
     964        3718 :     auxproc = &AuxiliaryProcs[proctype];
     965             : 
     966             :     Assert(MyProc == auxproc);
     967             : 
     968             :     /* Release any LW locks I am holding (see notes above) */
     969        3718 :     LWLockReleaseAll();
     970             : 
     971             :     /* Cancel any pending condition variable sleep, too */
     972        3718 :     ConditionVariableCancelSleep();
     973             : 
     974             :     /* look at the equivalent ProcKill() code for comments */
     975        3718 :     SwitchBackToLocalLatch();
     976        3718 :     pgstat_reset_wait_event_storage();
     977             : 
     978        3718 :     proc = MyProc;
     979        3718 :     MyProc = NULL;
     980        3718 :     DisownLatch(&proc->procLatch);
     981             : 
     982        3718 :     SpinLockAcquire(ProcStructLock);
     983             : 
     984             :     /* Mark auxiliary proc no longer in use */
     985        3718 :     proc->pid = 0;
     986             : 
     987             :     /* Update shared estimate of spins_per_delay */
     988        3718 :     ProcGlobal->spins_per_delay = update_spins_per_delay(ProcGlobal->spins_per_delay);
     989             : 
     990        3718 :     SpinLockRelease(ProcStructLock);
     991        3718 : }
     992             : 
     993             : /*
     994             :  * AuxiliaryPidGetProc -- get PGPROC for an auxiliary process
     995             :  * given its PID
     996             :  *
     997             :  * Returns NULL if not found.
     998             :  */
     999             : PGPROC *
    1000        3552 : AuxiliaryPidGetProc(int pid)
    1001             : {
    1002        3552 :     PGPROC     *result = NULL;
    1003             :     int         index;
    1004             : 
    1005        3552 :     if (pid == 0)               /* never match dummy PGPROCs */
    1006           0 :         return NULL;
    1007             : 
    1008        7242 :     for (index = 0; index < NUM_AUXILIARY_PROCS; index++)
    1009             :     {
    1010        7242 :         PGPROC     *proc = &AuxiliaryProcs[index];
    1011             : 
    1012        7242 :         if (proc->pid == pid)
    1013             :         {
    1014        3552 :             result = proc;
    1015        3552 :             break;
    1016             :         }
    1017             :     }
    1018        3552 :     return result;
    1019             : }
    1020             : 
    1021             : 
    1022             : /*
    1023             :  * ProcSleep -- put a process to sleep on the specified lock
    1024             :  *
    1025             :  * Caller must have set MyProc->heldLocks to reflect locks already held
    1026             :  * on the lockable object by this process (under all XIDs).
    1027             :  *
    1028             :  * The lock table's partition lock must be held at entry, and will be held
    1029             :  * at exit.
    1030             :  *
    1031             :  * Result: PROC_WAIT_STATUS_OK if we acquired the lock, PROC_WAIT_STATUS_ERROR if not (deadlock).
    1032             :  *
    1033             :  * ASSUME: that no one will fiddle with the queue until after
    1034             :  *      we release the partition lock.
    1035             :  *
    1036             :  * NOTES: The process queue is now a priority queue for locking.
    1037             :  */
    1038             : ProcWaitStatus
    1039        2068 : ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
    1040             : {
    1041        2068 :     LOCKMODE    lockmode = locallock->tag.mode;
    1042        2068 :     LOCK       *lock = locallock->lock;
    1043        2068 :     PROCLOCK   *proclock = locallock->proclock;
    1044        2068 :     uint32      hashcode = locallock->hashcode;
    1045        2068 :     LWLock     *partitionLock = LockHashPartitionLock(hashcode);
    1046        2068 :     dclist_head *waitQueue = &lock->waitProcs;
    1047        2068 :     PGPROC     *insert_before = NULL;
    1048        2068 :     LOCKMASK    myHeldLocks = MyProc->heldLocks;
    1049        2068 :     TimestampTz standbyWaitStart = 0;
    1050        2068 :     bool        early_deadlock = false;
    1051        2068 :     bool        allow_autovacuum_cancel = true;
    1052        2068 :     bool        logged_recovery_conflict = false;
    1053             :     ProcWaitStatus myWaitStatus;
    1054        2068 :     PGPROC     *leader = MyProc->lockGroupLeader;
    1055             : 
    1056             :     /*
    1057             :      * If group locking is in use, locks held by members of my locking group
    1058             :      * need to be included in myHeldLocks.  This is not required for relation
    1059             :      * extension lock which conflict among group members. However, including
    1060             :      * them in myHeldLocks will give group members the priority to get those
    1061             :      * locks as compared to other backends which are also trying to acquire
    1062             :      * those locks.  OTOH, we can avoid giving priority to group members for
    1063             :      * that kind of locks, but there doesn't appear to be a clear advantage of
    1064             :      * the same.
    1065             :      */
    1066        2068 :     if (leader != NULL)
    1067             :     {
    1068             :         dlist_iter  iter;
    1069             : 
    1070          60 :         dlist_foreach(iter, &lock->procLocks)
    1071             :         {
    1072             :             PROCLOCK   *otherproclock;
    1073             : 
    1074          46 :             otherproclock = dlist_container(PROCLOCK, lockLink, iter.cur);
    1075             : 
    1076          46 :             if (otherproclock->groupLeader == leader)
    1077          22 :                 myHeldLocks |= otherproclock->holdMask;
    1078             :         }
    1079             :     }
    1080             : 
    1081             :     /*
    1082             :      * Determine where to add myself in the wait queue.
    1083             :      *
    1084             :      * Normally I should go at the end of the queue.  However, if I already
    1085             :      * hold locks that conflict with the request of any previous waiter, put
    1086             :      * myself in the queue just in front of the first such waiter. This is not
    1087             :      * a necessary step, since deadlock detection would move me to before that
    1088             :      * waiter anyway; but it's relatively cheap to detect such a conflict
    1089             :      * immediately, and avoid delaying till deadlock timeout.
    1090             :      *
    1091             :      * Special case: if I find I should go in front of some waiter, check to
    1092             :      * see if I conflict with already-held locks or the requests before that
    1093             :      * waiter.  If not, then just grant myself the requested lock immediately.
    1094             :      * This is the same as the test for immediate grant in LockAcquire, except
    1095             :      * we are only considering the part of the wait queue before my insertion
    1096             :      * point.
    1097             :      */
    1098        2068 :     if (myHeldLocks != 0 && !dclist_is_empty(waitQueue))
    1099             :     {
    1100          10 :         LOCKMASK    aheadRequests = 0;
    1101             :         dlist_iter  iter;
    1102             : 
    1103          10 :         dclist_foreach(iter, waitQueue)
    1104             :         {
    1105          10 :             PGPROC     *proc = dlist_container(PGPROC, links, iter.cur);
    1106             : 
    1107             :             /*
    1108             :              * If we're part of the same locking group as this waiter, its
    1109             :              * locks neither conflict with ours nor contribute to
    1110             :              * aheadRequests.
    1111             :              */
    1112          10 :             if (leader != NULL && leader == proc->lockGroupLeader)
    1113           0 :                 continue;
    1114             : 
    1115             :             /* Must he wait for me? */
    1116          10 :             if (lockMethodTable->conflictTab[proc->waitLockMode] & myHeldLocks)
    1117             :             {
    1118             :                 /* Must I wait for him ? */
    1119          10 :                 if (lockMethodTable->conflictTab[lockmode] & proc->heldLocks)
    1120             :                 {
    1121             :                     /*
    1122             :                      * Yes, so we have a deadlock.  Easiest way to clean up
    1123             :                      * correctly is to call RemoveFromWaitQueue(), but we
    1124             :                      * can't do that until we are *on* the wait queue. So, set
    1125             :                      * a flag to check below, and break out of loop.  Also,
    1126             :                      * record deadlock info for later message.
    1127             :                      */
    1128           2 :                     RememberSimpleDeadLock(MyProc, lockmode, lock, proc);
    1129           2 :                     early_deadlock = true;
    1130           2 :                     break;
    1131             :                 }
    1132             :                 /* I must go before this waiter.  Check special case. */
    1133           8 :                 if ((lockMethodTable->conflictTab[lockmode] & aheadRequests) == 0 &&
    1134           8 :                     !LockCheckConflicts(lockMethodTable, lockmode, lock,
    1135             :                                         proclock))
    1136             :                 {
    1137             :                     /* Skip the wait and just grant myself the lock. */
    1138           8 :                     GrantLock(lock, proclock, lockmode);
    1139           8 :                     GrantAwaitedLock();
    1140           8 :                     return PROC_WAIT_STATUS_OK;
    1141             :                 }
    1142             : 
    1143             :                 /* Put myself into wait queue before conflicting process */
    1144           0 :                 insert_before = proc;
    1145           0 :                 break;
    1146             :             }
    1147             :             /* Nope, so advance to next waiter */
    1148           0 :             aheadRequests |= LOCKBIT_ON(proc->waitLockMode);
    1149             :         }
    1150             :     }
    1151             : 
    1152             :     /*
    1153             :      * Insert self into queue, at the position determined above.
    1154             :      */
    1155        2060 :     if (insert_before)
    1156           0 :         dclist_insert_before(waitQueue, &insert_before->links, &MyProc->links);
    1157             :     else
    1158        2060 :         dclist_push_tail(waitQueue, &MyProc->links);
    1159             : 
    1160        2060 :     lock->waitMask |= LOCKBIT_ON(lockmode);
    1161             : 
    1162             :     /* Set up wait information in PGPROC object, too */
    1163        2060 :     MyProc->waitLock = lock;
    1164        2060 :     MyProc->waitProcLock = proclock;
    1165        2060 :     MyProc->waitLockMode = lockmode;
    1166             : 
    1167        2060 :     MyProc->waitStatus = PROC_WAIT_STATUS_WAITING;
    1168             : 
    1169             :     /*
    1170             :      * If we detected deadlock, give up without waiting.  This must agree with
    1171             :      * CheckDeadLock's recovery code.
    1172             :      */
    1173        2060 :     if (early_deadlock)
    1174             :     {
    1175           2 :         RemoveFromWaitQueue(MyProc, hashcode);
    1176           2 :         return PROC_WAIT_STATUS_ERROR;
    1177             :     }
    1178             : 
    1179             :     /* mark that we are waiting for a lock */
    1180        2058 :     lockAwaited = locallock;
    1181             : 
    1182             :     /*
    1183             :      * Release the lock table's partition lock.
    1184             :      *
    1185             :      * NOTE: this may also cause us to exit critical-section state, possibly
    1186             :      * allowing a cancel/die interrupt to be accepted. This is OK because we
    1187             :      * have recorded the fact that we are waiting for a lock, and so
    1188             :      * LockErrorCleanup will clean up if cancel/die happens.
    1189             :      */
    1190        2058 :     LWLockRelease(partitionLock);
    1191             : 
    1192             :     /*
    1193             :      * Also, now that we will successfully clean up after an ereport, it's
    1194             :      * safe to check to see if there's a buffer pin deadlock against the
    1195             :      * Startup process.  Of course, that's only necessary if we're doing Hot
    1196             :      * Standby and are not the Startup process ourselves.
    1197             :      */
    1198        2058 :     if (RecoveryInProgress() && !InRecovery)
    1199           2 :         CheckRecoveryConflictDeadlock();
    1200             : 
    1201             :     /* Reset deadlock_state before enabling the timeout handler */
    1202        2058 :     deadlock_state = DS_NOT_YET_CHECKED;
    1203        2058 :     got_deadlock_timeout = false;
    1204             : 
    1205             :     /*
    1206             :      * Set timer so we can wake up after awhile and check for a deadlock. If a
    1207             :      * deadlock is detected, the handler sets MyProc->waitStatus =
    1208             :      * PROC_WAIT_STATUS_ERROR, allowing us to know that we must report failure
    1209             :      * rather than success.
    1210             :      *
    1211             :      * By delaying the check until we've waited for a bit, we can avoid
    1212             :      * running the rather expensive deadlock-check code in most cases.
    1213             :      *
    1214             :      * If LockTimeout is set, also enable the timeout for that.  We can save a
    1215             :      * few cycles by enabling both timeout sources in one call.
    1216             :      *
    1217             :      * If InHotStandby we set lock waits slightly later for clarity with other
    1218             :      * code.
    1219             :      */
    1220        2058 :     if (!InHotStandby)
    1221             :     {
    1222        2056 :         if (LockTimeout > 0)
    1223             :         {
    1224             :             EnableTimeoutParams timeouts[2];
    1225             : 
    1226         276 :             timeouts[0].id = DEADLOCK_TIMEOUT;
    1227         276 :             timeouts[0].type = TMPARAM_AFTER;
    1228         276 :             timeouts[0].delay_ms = DeadlockTimeout;
    1229         276 :             timeouts[1].id = LOCK_TIMEOUT;
    1230         276 :             timeouts[1].type = TMPARAM_AFTER;
    1231         276 :             timeouts[1].delay_ms = LockTimeout;
    1232         276 :             enable_timeouts(timeouts, 2);
    1233             :         }
    1234             :         else
    1235        1780 :             enable_timeout_after(DEADLOCK_TIMEOUT, DeadlockTimeout);
    1236             : 
    1237             :         /*
    1238             :          * Use the current time obtained for the deadlock timeout timer as
    1239             :          * waitStart (i.e., the time when this process started waiting for the
    1240             :          * lock). Since getting the current time newly can cause overhead, we
    1241             :          * reuse the already-obtained time to avoid that overhead.
    1242             :          *
    1243             :          * Note that waitStart is updated without holding the lock table's
    1244             :          * partition lock, to avoid the overhead by additional lock
    1245             :          * acquisition. This can cause "waitstart" in pg_locks to become NULL
    1246             :          * for a very short period of time after the wait started even though
    1247             :          * "granted" is false. This is OK in practice because we can assume
    1248             :          * that users are likely to look at "waitstart" when waiting for the
    1249             :          * lock for a long time.
    1250             :          */
    1251        2056 :         pg_atomic_write_u64(&MyProc->waitStart,
    1252        2056 :                             get_timeout_start_time(DEADLOCK_TIMEOUT));
    1253             :     }
    1254           2 :     else if (log_recovery_conflict_waits)
    1255             :     {
    1256             :         /*
    1257             :          * Set the wait start timestamp if logging is enabled and in hot
    1258             :          * standby.
    1259             :          */
    1260           2 :         standbyWaitStart = GetCurrentTimestamp();
    1261             :     }
    1262             : 
    1263             :     /*
    1264             :      * If somebody wakes us between LWLockRelease and WaitLatch, the latch
    1265             :      * will not wait. But a set latch does not necessarily mean that the lock
    1266             :      * is free now, as there are many other sources for latch sets than
    1267             :      * somebody releasing the lock.
    1268             :      *
    1269             :      * We process interrupts whenever the latch has been set, so cancel/die
    1270             :      * interrupts are processed quickly. This means we must not mind losing
    1271             :      * control to a cancel/die interrupt here.  We don't, because we have no
    1272             :      * shared-state-change work to do after being granted the lock (the
    1273             :      * grantor did it all).  We do have to worry about canceling the deadlock
    1274             :      * timeout and updating the locallock table, but if we lose control to an
    1275             :      * error, LockErrorCleanup will fix that up.
    1276             :      */
    1277             :     do
    1278             :     {
    1279        4712 :         if (InHotStandby)
    1280             :         {
    1281           8 :             bool        maybe_log_conflict =
    1282           8 :                 (standbyWaitStart != 0 && !logged_recovery_conflict);
    1283             : 
    1284             :             /* Set a timer and wait for that or for the lock to be granted */
    1285           8 :             ResolveRecoveryConflictWithLock(locallock->tag.lock,
    1286             :                                             maybe_log_conflict);
    1287             : 
    1288             :             /*
    1289             :              * Emit the log message if the startup process is waiting longer
    1290             :              * than deadlock_timeout for recovery conflict on lock.
    1291             :              */
    1292           8 :             if (maybe_log_conflict)
    1293             :             {
    1294           4 :                 TimestampTz now = GetCurrentTimestamp();
    1295             : 
    1296           4 :                 if (TimestampDifferenceExceeds(standbyWaitStart, now,
    1297             :                                                DeadlockTimeout))
    1298             :                 {
    1299             :                     VirtualTransactionId *vxids;
    1300             :                     int         cnt;
    1301             : 
    1302           2 :                     vxids = GetLockConflicts(&locallock->tag.lock,
    1303             :                                              AccessExclusiveLock, &cnt);
    1304             : 
    1305             :                     /*
    1306             :                      * Log the recovery conflict and the list of PIDs of
    1307             :                      * backends holding the conflicting lock. Note that we do
    1308             :                      * logging even if there are no such backends right now
    1309             :                      * because the startup process here has already waited
    1310             :                      * longer than deadlock_timeout.
    1311             :                      */
    1312           2 :                     LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_LOCK,
    1313             :                                         standbyWaitStart, now,
    1314           2 :                                         cnt > 0 ? vxids : NULL, true);
    1315           2 :                     logged_recovery_conflict = true;
    1316             :                 }
    1317             :             }
    1318             :         }
    1319             :         else
    1320             :         {
    1321        4704 :             (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
    1322        4704 :                              PG_WAIT_LOCK | locallock->tag.lock.locktag_type);
    1323        4704 :             ResetLatch(MyLatch);
    1324             :             /* check for deadlocks first, as that's probably log-worthy */
    1325        4704 :             if (got_deadlock_timeout)
    1326             :             {
    1327          44 :                 CheckDeadLock();
    1328          44 :                 got_deadlock_timeout = false;
    1329             :             }
    1330        4704 :             CHECK_FOR_INTERRUPTS();
    1331             :         }
    1332             : 
    1333             :         /*
    1334             :          * waitStatus could change from PROC_WAIT_STATUS_WAITING to something
    1335             :          * else asynchronously.  Read it just once per loop to prevent
    1336             :          * surprising behavior (such as missing log messages).
    1337             :          */
    1338        4628 :         myWaitStatus = *((volatile ProcWaitStatus *) &MyProc->waitStatus);
    1339             : 
    1340             :         /*
    1341             :          * If we are not deadlocked, but are waiting on an autovacuum-induced
    1342             :          * task, send a signal to interrupt it.
    1343             :          */
    1344        4628 :         if (deadlock_state == DS_BLOCKED_BY_AUTOVACUUM && allow_autovacuum_cancel)
    1345             :         {
    1346           0 :             PGPROC     *autovac = GetBlockingAutoVacuumPgproc();
    1347             :             uint8       statusFlags;
    1348             :             uint8       lockmethod_copy;
    1349             :             LOCKTAG     locktag_copy;
    1350             : 
    1351             :             /*
    1352             :              * Grab info we need, then release lock immediately.  Note this
    1353             :              * coding means that there is a tiny chance that the process
    1354             :              * terminates its current transaction and starts a different one
    1355             :              * before we have a change to send the signal; the worst possible
    1356             :              * consequence is that a for-wraparound vacuum is cancelled.  But
    1357             :              * that could happen in any case unless we were to do kill() with
    1358             :              * the lock held, which is much more undesirable.
    1359             :              */
    1360           0 :             LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
    1361           0 :             statusFlags = ProcGlobal->statusFlags[autovac->pgxactoff];
    1362           0 :             lockmethod_copy = lock->tag.locktag_lockmethodid;
    1363           0 :             locktag_copy = lock->tag;
    1364           0 :             LWLockRelease(ProcArrayLock);
    1365             : 
    1366             :             /*
    1367             :              * Only do it if the worker is not working to protect against Xid
    1368             :              * wraparound.
    1369             :              */
    1370           0 :             if ((statusFlags & PROC_IS_AUTOVACUUM) &&
    1371           0 :                 !(statusFlags & PROC_VACUUM_FOR_WRAPAROUND))
    1372             :             {
    1373           0 :                 int         pid = autovac->pid;
    1374             : 
    1375             :                 /* report the case, if configured to do so */
    1376           0 :                 if (message_level_is_interesting(DEBUG1))
    1377             :                 {
    1378             :                     StringInfoData locktagbuf;
    1379             :                     StringInfoData logbuf;  /* errdetail for server log */
    1380             : 
    1381           0 :                     initStringInfo(&locktagbuf);
    1382           0 :                     initStringInfo(&logbuf);
    1383           0 :                     DescribeLockTag(&locktagbuf, &locktag_copy);
    1384           0 :                     appendStringInfo(&logbuf,
    1385             :                                      "Process %d waits for %s on %s.",
    1386             :                                      MyProcPid,
    1387             :                                      GetLockmodeName(lockmethod_copy, lockmode),
    1388             :                                      locktagbuf.data);
    1389             : 
    1390           0 :                     ereport(DEBUG1,
    1391             :                             (errmsg_internal("sending cancel to blocking autovacuum PID %d",
    1392             :                                              pid),
    1393             :                              errdetail_log("%s", logbuf.data)));
    1394             : 
    1395           0 :                     pfree(locktagbuf.data);
    1396           0 :                     pfree(logbuf.data);
    1397             :                 }
    1398             : 
    1399             :                 /* send the autovacuum worker Back to Old Kent Road */
    1400           0 :                 if (kill(pid, SIGINT) < 0)
    1401             :                 {
    1402             :                     /*
    1403             :                      * There's a race condition here: once we release the
    1404             :                      * ProcArrayLock, it's possible for the autovac worker to
    1405             :                      * close up shop and exit before we can do the kill().
    1406             :                      * Therefore, we do not whinge about no-such-process.
    1407             :                      * Other errors such as EPERM could conceivably happen if
    1408             :                      * the kernel recycles the PID fast enough, but such cases
    1409             :                      * seem improbable enough that it's probably best to issue
    1410             :                      * a warning if we see some other errno.
    1411             :                      */
    1412           0 :                     if (errno != ESRCH)
    1413           0 :                         ereport(WARNING,
    1414             :                                 (errmsg("could not send signal to process %d: %m",
    1415             :                                         pid)));
    1416             :                 }
    1417             :             }
    1418             : 
    1419             :             /* prevent signal from being sent again more than once */
    1420           0 :             allow_autovacuum_cancel = false;
    1421             :         }
    1422             : 
    1423             :         /*
    1424             :          * If awoken after the deadlock check interrupt has run, and
    1425             :          * log_lock_waits is on, then report about the wait.
    1426             :          */
    1427        4628 :         if (log_lock_waits && deadlock_state != DS_NOT_YET_CHECKED)
    1428             :         {
    1429             :             StringInfoData buf,
    1430             :                         lock_waiters_sbuf,
    1431             :                         lock_holders_sbuf;
    1432             :             const char *modename;
    1433             :             long        secs;
    1434             :             int         usecs;
    1435             :             long        msecs;
    1436             :             dlist_iter  proc_iter;
    1437             :             PROCLOCK   *curproclock;
    1438          28 :             bool        first_holder = true,
    1439          28 :                         first_waiter = true;
    1440          28 :             int         lockHoldersNum = 0;
    1441             : 
    1442          28 :             initStringInfo(&buf);
    1443          28 :             initStringInfo(&lock_waiters_sbuf);
    1444          28 :             initStringInfo(&lock_holders_sbuf);
    1445             : 
    1446          28 :             DescribeLockTag(&buf, &locallock->tag.lock);
    1447          28 :             modename = GetLockmodeName(locallock->tag.lock.locktag_lockmethodid,
    1448             :                                        lockmode);
    1449          28 :             TimestampDifference(get_timeout_start_time(DEADLOCK_TIMEOUT),
    1450             :                                 GetCurrentTimestamp(),
    1451             :                                 &secs, &usecs);
    1452          28 :             msecs = secs * 1000 + usecs / 1000;
    1453          28 :             usecs = usecs % 1000;
    1454             : 
    1455             :             /*
    1456             :              * we loop over the lock's procLocks to gather a list of all
    1457             :              * holders and waiters. Thus we will be able to provide more
    1458             :              * detailed information for lock debugging purposes.
    1459             :              *
    1460             :              * lock->procLocks contains all processes which hold or wait for
    1461             :              * this lock.
    1462             :              */
    1463             : 
    1464          28 :             LWLockAcquire(partitionLock, LW_SHARED);
    1465             : 
    1466          98 :             dlist_foreach(proc_iter, &lock->procLocks)
    1467             :             {
    1468          70 :                 curproclock =
    1469          70 :                     dlist_container(PROCLOCK, lockLink, proc_iter.cur);
    1470             : 
    1471             :                 /*
    1472             :                  * we are a waiter if myProc->waitProcLock == curproclock; we
    1473             :                  * are a holder if it is NULL or something different
    1474             :                  */
    1475          70 :                 if (curproclock->tag.myProc->waitProcLock == curproclock)
    1476             :                 {
    1477          34 :                     if (first_waiter)
    1478             :                     {
    1479          16 :                         appendStringInfo(&lock_waiters_sbuf, "%d",
    1480          16 :                                          curproclock->tag.myProc->pid);
    1481          16 :                         first_waiter = false;
    1482             :                     }
    1483             :                     else
    1484          18 :                         appendStringInfo(&lock_waiters_sbuf, ", %d",
    1485          18 :                                          curproclock->tag.myProc->pid);
    1486             :                 }
    1487             :                 else
    1488             :                 {
    1489          36 :                     if (first_holder)
    1490             :                     {
    1491          28 :                         appendStringInfo(&lock_holders_sbuf, "%d",
    1492          28 :                                          curproclock->tag.myProc->pid);
    1493          28 :                         first_holder = false;
    1494             :                     }
    1495             :                     else
    1496           8 :                         appendStringInfo(&lock_holders_sbuf, ", %d",
    1497           8 :                                          curproclock->tag.myProc->pid);
    1498             : 
    1499          36 :                     lockHoldersNum++;
    1500             :                 }
    1501             :             }
    1502             : 
    1503          28 :             LWLockRelease(partitionLock);
    1504             : 
    1505          28 :             if (deadlock_state == DS_SOFT_DEADLOCK)
    1506           6 :                 ereport(LOG,
    1507             :                         (errmsg("process %d avoided deadlock for %s on %s by rearranging queue order after %ld.%03d ms",
    1508             :                                 MyProcPid, modename, buf.data, msecs, usecs),
    1509             :                          (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
    1510             :                                                "Processes holding the lock: %s. Wait queue: %s.",
    1511             :                                                lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
    1512          22 :             else if (deadlock_state == DS_HARD_DEADLOCK)
    1513             :             {
    1514             :                 /*
    1515             :                  * This message is a bit redundant with the error that will be
    1516             :                  * reported subsequently, but in some cases the error report
    1517             :                  * might not make it to the log (eg, if it's caught by an
    1518             :                  * exception handler), and we want to ensure all long-wait
    1519             :                  * events get logged.
    1520             :                  */
    1521           2 :                 ereport(LOG,
    1522             :                         (errmsg("process %d detected deadlock while waiting for %s on %s after %ld.%03d ms",
    1523             :                                 MyProcPid, modename, buf.data, msecs, usecs),
    1524             :                          (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
    1525             :                                                "Processes holding the lock: %s. Wait queue: %s.",
    1526             :                                                lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
    1527             :             }
    1528             : 
    1529          28 :             if (myWaitStatus == PROC_WAIT_STATUS_WAITING)
    1530          14 :                 ereport(LOG,
    1531             :                         (errmsg("process %d still waiting for %s on %s after %ld.%03d ms",
    1532             :                                 MyProcPid, modename, buf.data, msecs, usecs),
    1533             :                          (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
    1534             :                                                "Processes holding the lock: %s. Wait queue: %s.",
    1535             :                                                lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
    1536          14 :             else if (myWaitStatus == PROC_WAIT_STATUS_OK)
    1537          12 :                 ereport(LOG,
    1538             :                         (errmsg("process %d acquired %s on %s after %ld.%03d ms",
    1539             :                                 MyProcPid, modename, buf.data, msecs, usecs)));
    1540             :             else
    1541             :             {
    1542             :                 Assert(myWaitStatus == PROC_WAIT_STATUS_ERROR);
    1543             : 
    1544             :                 /*
    1545             :                  * Currently, the deadlock checker always kicks its own
    1546             :                  * process, which means that we'll only see
    1547             :                  * PROC_WAIT_STATUS_ERROR when deadlock_state ==
    1548             :                  * DS_HARD_DEADLOCK, and there's no need to print redundant
    1549             :                  * messages.  But for completeness and future-proofing, print
    1550             :                  * a message if it looks like someone else kicked us off the
    1551             :                  * lock.
    1552             :                  */
    1553           2 :                 if (deadlock_state != DS_HARD_DEADLOCK)
    1554           0 :                     ereport(LOG,
    1555             :                             (errmsg("process %d failed to acquire %s on %s after %ld.%03d ms",
    1556             :                                     MyProcPid, modename, buf.data, msecs, usecs),
    1557             :                              (errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
    1558             :                                                    "Processes holding the lock: %s. Wait queue: %s.",
    1559             :                                                    lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
    1560             :             }
    1561             : 
    1562             :             /*
    1563             :              * At this point we might still need to wait for the lock. Reset
    1564             :              * state so we don't print the above messages again.
    1565             :              */
    1566          28 :             deadlock_state = DS_NO_DEADLOCK;
    1567             : 
    1568          28 :             pfree(buf.data);
    1569          28 :             pfree(lock_holders_sbuf.data);
    1570          28 :             pfree(lock_waiters_sbuf.data);
    1571             :         }
    1572        4628 :     } while (myWaitStatus == PROC_WAIT_STATUS_WAITING);
    1573             : 
    1574             :     /*
    1575             :      * Disable the timers, if they are still running.  As in LockErrorCleanup,
    1576             :      * we must preserve the LOCK_TIMEOUT indicator flag: if a lock timeout has
    1577             :      * already caused QueryCancelPending to become set, we want the cancel to
    1578             :      * be reported as a lock timeout, not a user cancel.
    1579             :      */
    1580        1974 :     if (!InHotStandby)
    1581             :     {
    1582        1972 :         if (LockTimeout > 0)
    1583             :         {
    1584             :             DisableTimeoutParams timeouts[2];
    1585             : 
    1586         264 :             timeouts[0].id = DEADLOCK_TIMEOUT;
    1587         264 :             timeouts[0].keep_indicator = false;
    1588         264 :             timeouts[1].id = LOCK_TIMEOUT;
    1589         264 :             timeouts[1].keep_indicator = true;
    1590         264 :             disable_timeouts(timeouts, 2);
    1591             :         }
    1592             :         else
    1593        1708 :             disable_timeout(DEADLOCK_TIMEOUT, false);
    1594             :     }
    1595             : 
    1596             :     /*
    1597             :      * Emit the log message if recovery conflict on lock was resolved but the
    1598             :      * startup process waited longer than deadlock_timeout for it.
    1599             :      */
    1600        1974 :     if (InHotStandby && logged_recovery_conflict)
    1601           2 :         LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_LOCK,
    1602             :                             standbyWaitStart, GetCurrentTimestamp(),
    1603             :                             NULL, false);
    1604             : 
    1605             :     /*
    1606             :      * Re-acquire the lock table's partition lock.  We have to do this to hold
    1607             :      * off cancel/die interrupts before we can mess with lockAwaited (else we
    1608             :      * might have a missed or duplicated locallock update).
    1609             :      */
    1610        1974 :     LWLockAcquire(partitionLock, LW_EXCLUSIVE);
    1611             : 
    1612             :     /*
    1613             :      * We no longer want LockErrorCleanup to do anything.
    1614             :      */
    1615        1974 :     lockAwaited = NULL;
    1616             : 
    1617             :     /*
    1618             :      * If we got the lock, be sure to remember it in the locallock table.
    1619             :      */
    1620        1974 :     if (MyProc->waitStatus == PROC_WAIT_STATUS_OK)
    1621        1966 :         GrantAwaitedLock();
    1622             : 
    1623             :     /*
    1624             :      * We don't have to do anything else, because the awaker did all the
    1625             :      * necessary update of the lock table and MyProc.
    1626             :      */
    1627        1974 :     return MyProc->waitStatus;
    1628             : }
    1629             : 
    1630             : 
    1631             : /*
    1632             :  * ProcWakeup -- wake up a process by setting its latch.
    1633             :  *
    1634             :  *   Also remove the process from the wait queue and set its links invalid.
    1635             :  *
    1636             :  * The appropriate lock partition lock must be held by caller.
    1637             :  *
    1638             :  * XXX: presently, this code is only used for the "success" case, and only
    1639             :  * works correctly for that case.  To clean up in failure case, would need
    1640             :  * to twiddle the lock's request counts too --- see RemoveFromWaitQueue.
    1641             :  * Hence, in practice the waitStatus parameter must be PROC_WAIT_STATUS_OK.
    1642             :  */
    1643             : void
    1644        1974 : ProcWakeup(PGPROC *proc, ProcWaitStatus waitStatus)
    1645             : {
    1646        1974 :     if (dlist_node_is_detached(&proc->links))
    1647           0 :         return;
    1648             : 
    1649             :     Assert(proc->waitStatus == PROC_WAIT_STATUS_WAITING);
    1650             : 
    1651             :     /* Remove process from wait queue */
    1652        1974 :     dclist_delete_from_thoroughly(&proc->waitLock->waitProcs, &proc->links);
    1653             : 
    1654             :     /* Clean up process' state and pass it the ok/fail signal */
    1655        1974 :     proc->waitLock = NULL;
    1656        1974 :     proc->waitProcLock = NULL;
    1657        1974 :     proc->waitStatus = waitStatus;
    1658        1974 :     pg_atomic_write_u64(&MyProc->waitStart, 0);
    1659             : 
    1660             :     /* And awaken it */
    1661        1974 :     SetLatch(&proc->procLatch);
    1662             : }
    1663             : 
    1664             : /*
    1665             :  * ProcLockWakeup -- routine for waking up processes when a lock is
    1666             :  *      released (or a prior waiter is aborted).  Scan all waiters
    1667             :  *      for lock, waken any that are no longer blocked.
    1668             :  *
    1669             :  * The appropriate lock partition lock must be held by caller.
    1670             :  */
    1671             : void
    1672        2022 : ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock)
    1673             : {
    1674        2022 :     dclist_head *waitQueue = &lock->waitProcs;
    1675        2022 :     LOCKMASK    aheadRequests = 0;
    1676             :     dlist_mutable_iter miter;
    1677             : 
    1678        2022 :     if (dclist_is_empty(waitQueue))
    1679          88 :         return;
    1680             : 
    1681        4036 :     dclist_foreach_modify(miter, waitQueue)
    1682             :     {
    1683        2102 :         PGPROC     *proc = dlist_container(PGPROC, links, miter.cur);
    1684        2102 :         LOCKMODE    lockmode = proc->waitLockMode;
    1685             : 
    1686             :         /*
    1687             :          * Waken if (a) doesn't conflict with requests of earlier waiters, and
    1688             :          * (b) doesn't conflict with already-held locks.
    1689             :          */
    1690        2102 :         if ((lockMethodTable->conflictTab[lockmode] & aheadRequests) == 0 &&
    1691        2074 :             !LockCheckConflicts(lockMethodTable, lockmode, lock,
    1692             :                                 proc->waitProcLock))
    1693             :         {
    1694             :             /* OK to waken */
    1695        1974 :             GrantLock(lock, proc->waitProcLock, lockmode);
    1696             :             /* removes proc from the lock's waiting process queue */
    1697        1974 :             ProcWakeup(proc, PROC_WAIT_STATUS_OK);
    1698             :         }
    1699             :         else
    1700             :         {
    1701             :             /*
    1702             :              * Lock conflicts: Don't wake, but remember requested mode for
    1703             :              * later checks.
    1704             :              */
    1705         128 :             aheadRequests |= LOCKBIT_ON(lockmode);
    1706             :         }
    1707             :     }
    1708             : }
    1709             : 
    1710             : /*
    1711             :  * CheckDeadLock
    1712             :  *
    1713             :  * We only get to this routine, if DEADLOCK_TIMEOUT fired while waiting for a
    1714             :  * lock to be released by some other process.  Check if there's a deadlock; if
    1715             :  * not, just return.  (But signal ProcSleep to log a message, if
    1716             :  * log_lock_waits is true.)  If we have a real deadlock, remove ourselves from
    1717             :  * the lock's wait queue and signal an error to ProcSleep.
    1718             :  */
    1719             : static void
    1720          44 : CheckDeadLock(void)
    1721             : {
    1722             :     int         i;
    1723             : 
    1724             :     /*
    1725             :      * Acquire exclusive lock on the entire shared lock data structures. Must
    1726             :      * grab LWLocks in partition-number order to avoid LWLock deadlock.
    1727             :      *
    1728             :      * Note that the deadlock check interrupt had better not be enabled
    1729             :      * anywhere that this process itself holds lock partition locks, else this
    1730             :      * will wait forever.  Also note that LWLockAcquire creates a critical
    1731             :      * section, so that this routine cannot be interrupted by cancel/die
    1732             :      * interrupts.
    1733             :      */
    1734         748 :     for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
    1735         704 :         LWLockAcquire(LockHashPartitionLockByIndex(i), LW_EXCLUSIVE);
    1736             : 
    1737             :     /*
    1738             :      * Check to see if we've been awoken by anyone in the interim.
    1739             :      *
    1740             :      * If we have, we can return and resume our transaction -- happy day.
    1741             :      * Before we are awoken the process releasing the lock grants it to us so
    1742             :      * we know that we don't have to wait anymore.
    1743             :      *
    1744             :      * We check by looking to see if we've been unlinked from the wait queue.
    1745             :      * This is safe because we hold the lock partition lock.
    1746             :      */
    1747          44 :     if (MyProc->links.prev == NULL ||
    1748          44 :         MyProc->links.next == NULL)
    1749           0 :         goto check_done;
    1750             : 
    1751             : #ifdef LOCK_DEBUG
    1752             :     if (Debug_deadlocks)
    1753             :         DumpAllLocks();
    1754             : #endif
    1755             : 
    1756             :     /* Run the deadlock check, and set deadlock_state for use by ProcSleep */
    1757          44 :     deadlock_state = DeadLockCheck(MyProc);
    1758             : 
    1759          44 :     if (deadlock_state == DS_HARD_DEADLOCK)
    1760             :     {
    1761             :         /*
    1762             :          * Oops.  We have a deadlock.
    1763             :          *
    1764             :          * Get this process out of wait state. (Note: we could do this more
    1765             :          * efficiently by relying on lockAwaited, but use this coding to
    1766             :          * preserve the flexibility to kill some other transaction than the
    1767             :          * one detecting the deadlock.)
    1768             :          *
    1769             :          * RemoveFromWaitQueue sets MyProc->waitStatus to
    1770             :          * PROC_WAIT_STATUS_ERROR, so ProcSleep will report an error after we
    1771             :          * return from the signal handler.
    1772             :          */
    1773             :         Assert(MyProc->waitLock != NULL);
    1774           8 :         RemoveFromWaitQueue(MyProc, LockTagHashCode(&(MyProc->waitLock->tag)));
    1775             : 
    1776             :         /*
    1777             :          * We're done here.  Transaction abort caused by the error that
    1778             :          * ProcSleep will raise will cause any other locks we hold to be
    1779             :          * released, thus allowing other processes to wake up; we don't need
    1780             :          * to do that here.  NOTE: an exception is that releasing locks we
    1781             :          * hold doesn't consider the possibility of waiters that were blocked
    1782             :          * behind us on the lock we just failed to get, and might now be
    1783             :          * wakable because we're not in front of them anymore.  However,
    1784             :          * RemoveFromWaitQueue took care of waking up any such processes.
    1785             :          */
    1786             :     }
    1787             : 
    1788             :     /*
    1789             :      * And release locks.  We do this in reverse order for two reasons: (1)
    1790             :      * Anyone else who needs more than one of the locks will be trying to lock
    1791             :      * them in increasing order; we don't want to release the other process
    1792             :      * until it can get all the locks it needs. (2) This avoids O(N^2)
    1793             :      * behavior inside LWLockRelease.
    1794             :      */
    1795          36 : check_done:
    1796         748 :     for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
    1797         704 :         LWLockRelease(LockHashPartitionLockByIndex(i));
    1798          44 : }
    1799             : 
    1800             : /*
    1801             :  * CheckDeadLockAlert - Handle the expiry of deadlock_timeout.
    1802             :  *
    1803             :  * NB: Runs inside a signal handler, be careful.
    1804             :  */
    1805             : void
    1806          44 : CheckDeadLockAlert(void)
    1807             : {
    1808          44 :     int         save_errno = errno;
    1809             : 
    1810          44 :     got_deadlock_timeout = true;
    1811             : 
    1812             :     /*
    1813             :      * Have to set the latch again, even if handle_sig_alarm already did. Back
    1814             :      * then got_deadlock_timeout wasn't yet set... It's unlikely that this
    1815             :      * ever would be a problem, but setting a set latch again is cheap.
    1816             :      *
    1817             :      * Note that, when this function runs inside procsignal_sigusr1_handler(),
    1818             :      * the handler function sets the latch again after the latch is set here.
    1819             :      */
    1820          44 :     SetLatch(MyLatch);
    1821          44 :     errno = save_errno;
    1822          44 : }
    1823             : 
    1824             : /*
    1825             :  * ProcWaitForSignal - wait for a signal from another backend.
    1826             :  *
    1827             :  * As this uses the generic process latch the caller has to be robust against
    1828             :  * unrelated wakeups: Always check that the desired state has occurred, and
    1829             :  * wait again if not.
    1830             :  */
    1831             : void
    1832          34 : ProcWaitForSignal(uint32 wait_event_info)
    1833             : {
    1834          34 :     (void) WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH, 0,
    1835             :                      wait_event_info);
    1836          34 :     ResetLatch(MyLatch);
    1837          34 :     CHECK_FOR_INTERRUPTS();
    1838          34 : }
    1839             : 
    1840             : /*
    1841             :  * ProcSendSignal - set the latch of a backend identified by pgprocno
    1842             :  */
    1843             : void
    1844           6 : ProcSendSignal(int pgprocno)
    1845             : {
    1846           6 :     if (pgprocno < 0 || pgprocno >= ProcGlobal->allProcCount)
    1847           0 :         elog(ERROR, "pgprocno out of range");
    1848             : 
    1849           6 :     SetLatch(&ProcGlobal->allProcs[pgprocno].procLatch);
    1850           6 : }
    1851             : 
    1852             : /*
    1853             :  * BecomeLockGroupLeader - designate process as lock group leader
    1854             :  *
    1855             :  * Once this function has returned, other processes can join the lock group
    1856             :  * by calling BecomeLockGroupMember.
    1857             :  */
    1858             : void
    1859        1062 : BecomeLockGroupLeader(void)
    1860             : {
    1861             :     LWLock     *leader_lwlock;
    1862             : 
    1863             :     /* If we already did it, we don't need to do it again. */
    1864        1062 :     if (MyProc->lockGroupLeader == MyProc)
    1865         954 :         return;
    1866             : 
    1867             :     /* We had better not be a follower. */
    1868             :     Assert(MyProc->lockGroupLeader == NULL);
    1869             : 
    1870             :     /* Create single-member group, containing only ourselves. */
    1871         108 :     leader_lwlock = LockHashPartitionLockByProc(MyProc);
    1872         108 :     LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
    1873         108 :     MyProc->lockGroupLeader = MyProc;
    1874         108 :     dlist_push_head(&MyProc->lockGroupMembers, &MyProc->lockGroupLink);
    1875         108 :     LWLockRelease(leader_lwlock);
    1876             : }
    1877             : 
    1878             : /*
    1879             :  * BecomeLockGroupMember - designate process as lock group member
    1880             :  *
    1881             :  * This is pretty straightforward except for the possibility that the leader
    1882             :  * whose group we're trying to join might exit before we manage to do so;
    1883             :  * and the PGPROC might get recycled for an unrelated process.  To avoid
    1884             :  * that, we require the caller to pass the PID of the intended PGPROC as
    1885             :  * an interlock.  Returns true if we successfully join the intended lock
    1886             :  * group, and false if not.
    1887             :  */
    1888             : bool
    1889        2592 : BecomeLockGroupMember(PGPROC *leader, int pid)
    1890             : {
    1891             :     LWLock     *leader_lwlock;
    1892        2592 :     bool        ok = false;
    1893             : 
    1894             :     /* Group leader can't become member of group */
    1895             :     Assert(MyProc != leader);
    1896             : 
    1897             :     /* Can't already be a member of a group */
    1898             :     Assert(MyProc->lockGroupLeader == NULL);
    1899             : 
    1900             :     /* PID must be valid. */
    1901             :     Assert(pid != 0);
    1902             : 
    1903             :     /*
    1904             :      * Get lock protecting the group fields.  Note LockHashPartitionLockByProc
    1905             :      * accesses leader->pgprocno in a PGPROC that might be free.  This is safe
    1906             :      * because all PGPROCs' pgprocno fields are set during shared memory
    1907             :      * initialization and never change thereafter; so we will acquire the
    1908             :      * correct lock even if the leader PGPROC is in process of being recycled.
    1909             :      */
    1910        2592 :     leader_lwlock = LockHashPartitionLockByProc(leader);
    1911        2592 :     LWLockAcquire(leader_lwlock, LW_EXCLUSIVE);
    1912             : 
    1913             :     /* Is this the leader we're looking for? */
    1914        2592 :     if (leader->pid == pid && leader->lockGroupLeader == leader)
    1915             :     {
    1916             :         /* OK, join the group */
    1917        2592 :         ok = true;
    1918        2592 :         MyProc->lockGroupLeader = leader;
    1919        2592 :         dlist_push_tail(&leader->lockGroupMembers, &MyProc->lockGroupLink);
    1920             :     }
    1921        2592 :     LWLockRelease(leader_lwlock);
    1922             : 
    1923        2592 :     return ok;
    1924             : }

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