LCOV - code coverage report
Current view: top level - src/backend/storage/lmgr - deadlock.c (source / functions) Hit Total Coverage
Test: PostgreSQL 17devel Lines: 257 298 86.2 %
Date: 2024-03-28 09:11:01 Functions: 11 12 91.7 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * deadlock.c
       4             :  *    POSTGRES deadlock detection code
       5             :  *
       6             :  * See src/backend/storage/lmgr/README for a description of the deadlock
       7             :  * detection and resolution algorithms.
       8             :  *
       9             :  *
      10             :  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
      11             :  * Portions Copyright (c) 1994, Regents of the University of California
      12             :  *
      13             :  *
      14             :  * IDENTIFICATION
      15             :  *    src/backend/storage/lmgr/deadlock.c
      16             :  *
      17             :  *  Interface:
      18             :  *
      19             :  *  DeadLockCheck()
      20             :  *  DeadLockReport()
      21             :  *  RememberSimpleDeadLock()
      22             :  *  InitDeadLockChecking()
      23             :  *
      24             :  *-------------------------------------------------------------------------
      25             :  */
      26             : #include "postgres.h"
      27             : 
      28             : #include "miscadmin.h"
      29             : #include "pg_trace.h"
      30             : #include "pgstat.h"
      31             : #include "storage/lmgr.h"
      32             : #include "storage/proc.h"
      33             : #include "utils/memutils.h"
      34             : 
      35             : 
      36             : /*
      37             :  * One edge in the waits-for graph.
      38             :  *
      39             :  * waiter and blocker may or may not be members of a lock group, but if either
      40             :  * is, it will be the leader rather than any other member of the lock group.
      41             :  * The group leaders act as representatives of the whole group even though
      42             :  * those particular processes need not be waiting at all.  There will be at
      43             :  * least one member of the waiter's lock group on the wait queue for the given
      44             :  * lock, maybe more.
      45             :  */
      46             : typedef struct
      47             : {
      48             :     PGPROC     *waiter;         /* the leader of the waiting lock group */
      49             :     PGPROC     *blocker;        /* the leader of the group it is waiting for */
      50             :     LOCK       *lock;           /* the lock being waited for */
      51             :     int         pred;           /* workspace for TopoSort */
      52             :     int         link;           /* workspace for TopoSort */
      53             : } EDGE;
      54             : 
      55             : /* One potential reordering of a lock's wait queue */
      56             : typedef struct
      57             : {
      58             :     LOCK       *lock;           /* the lock whose wait queue is described */
      59             :     PGPROC    **procs;          /* array of PGPROC *'s in new wait order */
      60             :     int         nProcs;
      61             : } WAIT_ORDER;
      62             : 
      63             : /*
      64             :  * Information saved about each edge in a detected deadlock cycle.  This
      65             :  * is used to print a diagnostic message upon failure.
      66             :  *
      67             :  * Note: because we want to examine this info after releasing the lock
      68             :  * manager's partition locks, we can't just store LOCK and PGPROC pointers;
      69             :  * we must extract out all the info we want to be able to print.
      70             :  */
      71             : typedef struct
      72             : {
      73             :     LOCKTAG     locktag;        /* ID of awaited lock object */
      74             :     LOCKMODE    lockmode;       /* type of lock we're waiting for */
      75             :     int         pid;            /* PID of blocked backend */
      76             : } DEADLOCK_INFO;
      77             : 
      78             : 
      79             : static bool DeadLockCheckRecurse(PGPROC *proc);
      80             : static int  TestConfiguration(PGPROC *startProc);
      81             : static bool FindLockCycle(PGPROC *checkProc,
      82             :                           EDGE *softEdges, int *nSoftEdges);
      83             : static bool FindLockCycleRecurse(PGPROC *checkProc, int depth,
      84             :                                  EDGE *softEdges, int *nSoftEdges);
      85             : static bool FindLockCycleRecurseMember(PGPROC *checkProc,
      86             :                                        PGPROC *checkProcLeader,
      87             :                                        int depth, EDGE *softEdges, int *nSoftEdges);
      88             : static bool ExpandConstraints(EDGE *constraints, int nConstraints);
      89             : static bool TopoSort(LOCK *lock, EDGE *constraints, int nConstraints,
      90             :                      PGPROC **ordering);
      91             : 
      92             : #ifdef DEBUG_DEADLOCK
      93             : static void PrintLockQueue(LOCK *lock, const char *info);
      94             : #endif
      95             : 
      96             : 
      97             : /*
      98             :  * Working space for the deadlock detector
      99             :  */
     100             : 
     101             : /* Workspace for FindLockCycle */
     102             : static PGPROC **visitedProcs;   /* Array of visited procs */
     103             : static int  nVisitedProcs;
     104             : 
     105             : /* Workspace for TopoSort */
     106             : static PGPROC **topoProcs;      /* Array of not-yet-output procs */
     107             : static int *beforeConstraints;  /* Counts of remaining before-constraints */
     108             : static int *afterConstraints;   /* List head for after-constraints */
     109             : 
     110             : /* Output area for ExpandConstraints */
     111             : static WAIT_ORDER *waitOrders;  /* Array of proposed queue rearrangements */
     112             : static int  nWaitOrders;
     113             : static PGPROC **waitOrderProcs; /* Space for waitOrders queue contents */
     114             : 
     115             : /* Current list of constraints being considered */
     116             : static EDGE *curConstraints;
     117             : static int  nCurConstraints;
     118             : static int  maxCurConstraints;
     119             : 
     120             : /* Storage space for results from FindLockCycle */
     121             : static EDGE *possibleConstraints;
     122             : static int  nPossibleConstraints;
     123             : static int  maxPossibleConstraints;
     124             : static DEADLOCK_INFO *deadlockDetails;
     125             : static int  nDeadlockDetails;
     126             : 
     127             : /* PGPROC pointer of any blocking autovacuum worker found */
     128             : static PGPROC *blocking_autovacuum_proc = NULL;
     129             : 
     130             : 
     131             : /*
     132             :  * InitDeadLockChecking -- initialize deadlock checker during backend startup
     133             :  *
     134             :  * This does per-backend initialization of the deadlock checker; primarily,
     135             :  * allocation of working memory for DeadLockCheck.  We do this per-backend
     136             :  * since there's no percentage in making the kernel do copy-on-write
     137             :  * inheritance of workspace from the postmaster.  We want to allocate the
     138             :  * space at startup because (a) the deadlock checker might be invoked when
     139             :  * there's no free memory left, and (b) the checker is normally run inside a
     140             :  * signal handler, which is a very dangerous place to invoke palloc from.
     141             :  */
     142             : void
     143       25636 : InitDeadLockChecking(void)
     144             : {
     145             :     MemoryContext oldcxt;
     146             : 
     147             :     /* Make sure allocations are permanent */
     148       25636 :     oldcxt = MemoryContextSwitchTo(TopMemoryContext);
     149             : 
     150             :     /*
     151             :      * FindLockCycle needs at most MaxBackends entries in visitedProcs[] and
     152             :      * deadlockDetails[].
     153             :      */
     154       25636 :     visitedProcs = (PGPROC **) palloc(MaxBackends * sizeof(PGPROC *));
     155       25636 :     deadlockDetails = (DEADLOCK_INFO *) palloc(MaxBackends * sizeof(DEADLOCK_INFO));
     156             : 
     157             :     /*
     158             :      * TopoSort needs to consider at most MaxBackends wait-queue entries, and
     159             :      * it needn't run concurrently with FindLockCycle.
     160             :      */
     161       25636 :     topoProcs = visitedProcs;   /* re-use this space */
     162       25636 :     beforeConstraints = (int *) palloc(MaxBackends * sizeof(int));
     163       25636 :     afterConstraints = (int *) palloc(MaxBackends * sizeof(int));
     164             : 
     165             :     /*
     166             :      * We need to consider rearranging at most MaxBackends/2 wait queues
     167             :      * (since it takes at least two waiters in a queue to create a soft edge),
     168             :      * and the expanded form of the wait queues can't involve more than
     169             :      * MaxBackends total waiters.
     170             :      */
     171       25636 :     waitOrders = (WAIT_ORDER *)
     172       25636 :         palloc((MaxBackends / 2) * sizeof(WAIT_ORDER));
     173       25636 :     waitOrderProcs = (PGPROC **) palloc(MaxBackends * sizeof(PGPROC *));
     174             : 
     175             :     /*
     176             :      * Allow at most MaxBackends distinct constraints in a configuration. (Is
     177             :      * this enough?  In practice it seems it should be, but I don't quite see
     178             :      * how to prove it.  If we run out, we might fail to find a workable wait
     179             :      * queue rearrangement even though one exists.)  NOTE that this number
     180             :      * limits the maximum recursion depth of DeadLockCheckRecurse. Making it
     181             :      * really big might potentially allow a stack-overflow problem.
     182             :      */
     183       25636 :     maxCurConstraints = MaxBackends;
     184       25636 :     curConstraints = (EDGE *) palloc(maxCurConstraints * sizeof(EDGE));
     185             : 
     186             :     /*
     187             :      * Allow up to 3*MaxBackends constraints to be saved without having to
     188             :      * re-run TestConfiguration.  (This is probably more than enough, but we
     189             :      * can survive if we run low on space by doing excess runs of
     190             :      * TestConfiguration to re-compute constraint lists each time needed.) The
     191             :      * last MaxBackends entries in possibleConstraints[] are reserved as
     192             :      * output workspace for FindLockCycle.
     193             :      */
     194       25636 :     maxPossibleConstraints = MaxBackends * 4;
     195       25636 :     possibleConstraints =
     196       25636 :         (EDGE *) palloc(maxPossibleConstraints * sizeof(EDGE));
     197             : 
     198       25636 :     MemoryContextSwitchTo(oldcxt);
     199       25636 : }
     200             : 
     201             : /*
     202             :  * DeadLockCheck -- Checks for deadlocks for a given process
     203             :  *
     204             :  * This code looks for deadlocks involving the given process.  If any
     205             :  * are found, it tries to rearrange lock wait queues to resolve the
     206             :  * deadlock.  If resolution is impossible, return DS_HARD_DEADLOCK ---
     207             :  * the caller is then expected to abort the given proc's transaction.
     208             :  *
     209             :  * Caller must already have locked all partitions of the lock tables.
     210             :  *
     211             :  * On failure, deadlock details are recorded in deadlockDetails[] for
     212             :  * subsequent printing by DeadLockReport().  That activity is separate
     213             :  * because (a) we don't want to do it while holding all those LWLocks,
     214             :  * and (b) we are typically invoked inside a signal handler.
     215             :  */
     216             : DeadLockState
     217          44 : DeadLockCheck(PGPROC *proc)
     218             : {
     219             :     /* Initialize to "no constraints" */
     220          44 :     nCurConstraints = 0;
     221          44 :     nPossibleConstraints = 0;
     222          44 :     nWaitOrders = 0;
     223             : 
     224             :     /* Initialize to not blocked by an autovacuum worker */
     225          44 :     blocking_autovacuum_proc = NULL;
     226             : 
     227             :     /* Search for deadlocks and possible fixes */
     228          44 :     if (DeadLockCheckRecurse(proc))
     229             :     {
     230             :         /*
     231             :          * Call FindLockCycle one more time, to record the correct
     232             :          * deadlockDetails[] for the basic state with no rearrangements.
     233             :          */
     234             :         int         nSoftEdges;
     235             : 
     236             :         TRACE_POSTGRESQL_DEADLOCK_FOUND();
     237             : 
     238           8 :         nWaitOrders = 0;
     239           8 :         if (!FindLockCycle(proc, possibleConstraints, &nSoftEdges))
     240           0 :             elog(FATAL, "deadlock seems to have disappeared");
     241             : 
     242           8 :         return DS_HARD_DEADLOCK;    /* cannot find a non-deadlocked state */
     243             :     }
     244             : 
     245             :     /* Apply any needed rearrangements of wait queues */
     246          42 :     for (int i = 0; i < nWaitOrders; i++)
     247             :     {
     248           6 :         LOCK       *lock = waitOrders[i].lock;
     249           6 :         PGPROC    **procs = waitOrders[i].procs;
     250           6 :         int         nProcs = waitOrders[i].nProcs;
     251           6 :         dclist_head *waitQueue = &lock->waitProcs;
     252             : 
     253             :         Assert(nProcs == dclist_count(waitQueue));
     254             : 
     255             : #ifdef DEBUG_DEADLOCK
     256             :         PrintLockQueue(lock, "DeadLockCheck:");
     257             : #endif
     258             : 
     259             :         /* Reset the queue and re-add procs in the desired order */
     260           6 :         dclist_init(waitQueue);
     261          24 :         for (int j = 0; j < nProcs; j++)
     262          18 :             dclist_push_tail(waitQueue, &procs[j]->links);
     263             : 
     264             : #ifdef DEBUG_DEADLOCK
     265             :         PrintLockQueue(lock, "rearranged to:");
     266             : #endif
     267             : 
     268             :         /* See if any waiters for the lock can be woken up now */
     269           6 :         ProcLockWakeup(GetLocksMethodTable(lock), lock);
     270             :     }
     271             : 
     272             :     /* Return code tells caller if we had to escape a deadlock or not */
     273          36 :     if (nWaitOrders > 0)
     274           6 :         return DS_SOFT_DEADLOCK;
     275          30 :     else if (blocking_autovacuum_proc != NULL)
     276           0 :         return DS_BLOCKED_BY_AUTOVACUUM;
     277             :     else
     278          30 :         return DS_NO_DEADLOCK;
     279             : }
     280             : 
     281             : /*
     282             :  * Return the PGPROC of the autovacuum that's blocking a process.
     283             :  *
     284             :  * We reset the saved pointer as soon as we pass it back.
     285             :  */
     286             : PGPROC *
     287           0 : GetBlockingAutoVacuumPgproc(void)
     288             : {
     289             :     PGPROC     *ptr;
     290             : 
     291           0 :     ptr = blocking_autovacuum_proc;
     292           0 :     blocking_autovacuum_proc = NULL;
     293             : 
     294           0 :     return ptr;
     295             : }
     296             : 
     297             : /*
     298             :  * DeadLockCheckRecurse -- recursively search for valid orderings
     299             :  *
     300             :  * curConstraints[] holds the current set of constraints being considered
     301             :  * by an outer level of recursion.  Add to this each possible solution
     302             :  * constraint for any cycle detected at this level.
     303             :  *
     304             :  * Returns true if no solution exists.  Returns false if a deadlock-free
     305             :  * state is attainable, in which case waitOrders[] shows the required
     306             :  * rearrangements of lock wait queues (if any).
     307             :  */
     308             : static bool
     309          50 : DeadLockCheckRecurse(PGPROC *proc)
     310             : {
     311             :     int         nEdges;
     312             :     int         oldPossibleConstraints;
     313             :     bool        savedList;
     314             :     int         i;
     315             : 
     316          50 :     nEdges = TestConfiguration(proc);
     317          50 :     if (nEdges < 0)
     318           8 :         return true;            /* hard deadlock --- no solution */
     319          42 :     if (nEdges == 0)
     320          36 :         return false;           /* good configuration found */
     321           6 :     if (nCurConstraints >= maxCurConstraints)
     322           0 :         return true;            /* out of room for active constraints? */
     323           6 :     oldPossibleConstraints = nPossibleConstraints;
     324           6 :     if (nPossibleConstraints + nEdges + MaxBackends <= maxPossibleConstraints)
     325             :     {
     326             :         /* We can save the edge list in possibleConstraints[] */
     327           6 :         nPossibleConstraints += nEdges;
     328           6 :         savedList = true;
     329             :     }
     330             :     else
     331             :     {
     332             :         /* Not room; will need to regenerate the edges on-the-fly */
     333           0 :         savedList = false;
     334             :     }
     335             : 
     336             :     /*
     337             :      * Try each available soft edge as an addition to the configuration.
     338             :      */
     339           6 :     for (i = 0; i < nEdges; i++)
     340             :     {
     341           6 :         if (!savedList && i > 0)
     342             :         {
     343             :             /* Regenerate the list of possible added constraints */
     344           0 :             if (nEdges != TestConfiguration(proc))
     345           0 :                 elog(FATAL, "inconsistent results during deadlock check");
     346             :         }
     347           6 :         curConstraints[nCurConstraints] =
     348           6 :             possibleConstraints[oldPossibleConstraints + i];
     349           6 :         nCurConstraints++;
     350           6 :         if (!DeadLockCheckRecurse(proc))
     351           6 :             return false;       /* found a valid solution! */
     352             :         /* give up on that added constraint, try again */
     353           0 :         nCurConstraints--;
     354             :     }
     355           0 :     nPossibleConstraints = oldPossibleConstraints;
     356           0 :     return true;                /* no solution found */
     357             : }
     358             : 
     359             : 
     360             : /*--------------------
     361             :  * Test a configuration (current set of constraints) for validity.
     362             :  *
     363             :  * Returns:
     364             :  *      0: the configuration is good (no deadlocks)
     365             :  *     -1: the configuration has a hard deadlock or is not self-consistent
     366             :  *      >0: the configuration has one or more soft deadlocks
     367             :  *
     368             :  * In the soft-deadlock case, one of the soft cycles is chosen arbitrarily
     369             :  * and a list of its soft edges is returned beginning at
     370             :  * possibleConstraints+nPossibleConstraints.  The return value is the
     371             :  * number of soft edges.
     372             :  *--------------------
     373             :  */
     374             : static int
     375          50 : TestConfiguration(PGPROC *startProc)
     376             : {
     377          50 :     int         softFound = 0;
     378          50 :     EDGE       *softEdges = possibleConstraints + nPossibleConstraints;
     379             :     int         nSoftEdges;
     380             :     int         i;
     381             : 
     382             :     /*
     383             :      * Make sure we have room for FindLockCycle's output.
     384             :      */
     385          50 :     if (nPossibleConstraints + MaxBackends > maxPossibleConstraints)
     386           0 :         return -1;
     387             : 
     388             :     /*
     389             :      * Expand current constraint set into wait orderings.  Fail if the
     390             :      * constraint set is not self-consistent.
     391             :      */
     392          50 :     if (!ExpandConstraints(curConstraints, nCurConstraints))
     393           0 :         return -1;
     394             : 
     395             :     /*
     396             :      * Check for cycles involving startProc or any of the procs mentioned in
     397             :      * constraints.  We check startProc last because if it has a soft cycle
     398             :      * still to be dealt with, we want to deal with that first.
     399             :      */
     400          56 :     for (i = 0; i < nCurConstraints; i++)
     401             :     {
     402           6 :         if (FindLockCycle(curConstraints[i].waiter, softEdges, &nSoftEdges))
     403             :         {
     404           0 :             if (nSoftEdges == 0)
     405           0 :                 return -1;      /* hard deadlock detected */
     406           0 :             softFound = nSoftEdges;
     407             :         }
     408           6 :         if (FindLockCycle(curConstraints[i].blocker, softEdges, &nSoftEdges))
     409             :         {
     410           0 :             if (nSoftEdges == 0)
     411           0 :                 return -1;      /* hard deadlock detected */
     412           0 :             softFound = nSoftEdges;
     413             :         }
     414             :     }
     415          50 :     if (FindLockCycle(startProc, softEdges, &nSoftEdges))
     416             :     {
     417          14 :         if (nSoftEdges == 0)
     418           8 :             return -1;          /* hard deadlock detected */
     419           6 :         softFound = nSoftEdges;
     420             :     }
     421          42 :     return softFound;
     422             : }
     423             : 
     424             : 
     425             : /*
     426             :  * FindLockCycle -- basic check for deadlock cycles
     427             :  *
     428             :  * Scan outward from the given proc to see if there is a cycle in the
     429             :  * waits-for graph that includes this proc.  Return true if a cycle
     430             :  * is found, else false.  If a cycle is found, we return a list of
     431             :  * the "soft edges", if any, included in the cycle.  These edges could
     432             :  * potentially be eliminated by rearranging wait queues.  We also fill
     433             :  * deadlockDetails[] with information about the detected cycle; this info
     434             :  * is not used by the deadlock algorithm itself, only to print a useful
     435             :  * message after failing.
     436             :  *
     437             :  * Since we need to be able to check hypothetical configurations that would
     438             :  * exist after wait queue rearrangement, the routine pays attention to the
     439             :  * table of hypothetical queue orders in waitOrders[].  These orders will
     440             :  * be believed in preference to the actual ordering seen in the locktable.
     441             :  */
     442             : static bool
     443          70 : FindLockCycle(PGPROC *checkProc,
     444             :               EDGE *softEdges,  /* output argument */
     445             :               int *nSoftEdges)  /* output argument */
     446             : {
     447          70 :     nVisitedProcs = 0;
     448          70 :     nDeadlockDetails = 0;
     449          70 :     *nSoftEdges = 0;
     450          70 :     return FindLockCycleRecurse(checkProc, 0, softEdges, nSoftEdges);
     451             : }
     452             : 
     453             : static bool
     454         222 : FindLockCycleRecurse(PGPROC *checkProc,
     455             :                      int depth,
     456             :                      EDGE *softEdges,   /* output argument */
     457             :                      int *nSoftEdges)   /* output argument */
     458             : {
     459             :     int         i;
     460             :     dlist_iter  iter;
     461             : 
     462             :     /*
     463             :      * If this process is a lock group member, check the leader instead. (Note
     464             :      * that we might be the leader, in which case this is a no-op.)
     465             :      */
     466         222 :     if (checkProc->lockGroupLeader != NULL)
     467          52 :         checkProc = checkProc->lockGroupLeader;
     468             : 
     469             :     /*
     470             :      * Have we already seen this proc?
     471             :      */
     472         494 :     for (i = 0; i < nVisitedProcs; i++)
     473             :     {
     474         306 :         if (visitedProcs[i] == checkProc)
     475             :         {
     476             :             /* If we return to starting point, we have a deadlock cycle */
     477          34 :             if (i == 0)
     478             :             {
     479             :                 /*
     480             :                  * record total length of cycle --- outer levels will now fill
     481             :                  * deadlockDetails[]
     482             :                  */
     483             :                 Assert(depth <= MaxBackends);
     484          22 :                 nDeadlockDetails = depth;
     485             : 
     486          22 :                 return true;
     487             :             }
     488             : 
     489             :             /*
     490             :              * Otherwise, we have a cycle but it does not include the start
     491             :              * point, so say "no deadlock".
     492             :              */
     493          12 :             return false;
     494             :         }
     495             :     }
     496             :     /* Mark proc as seen */
     497             :     Assert(nVisitedProcs < MaxBackends);
     498         188 :     visitedProcs[nVisitedProcs++] = checkProc;
     499             : 
     500             :     /*
     501             :      * If the process is waiting, there is an outgoing waits-for edge to each
     502             :      * process that blocks it.
     503             :      */
     504         318 :     if (checkProc->links.next != NULL && checkProc->waitLock != NULL &&
     505         130 :         FindLockCycleRecurseMember(checkProc, checkProc, depth, softEdges,
     506             :                                    nSoftEdges))
     507          74 :         return true;
     508             : 
     509             :     /*
     510             :      * If the process is not waiting, there could still be outgoing waits-for
     511             :      * edges if it is part of a lock group, because other members of the lock
     512             :      * group might be waiting even though this process is not.  (Given lock
     513             :      * groups {A1, A2} and {B1, B2}, if A1 waits for B1 and B2 waits for A2,
     514             :      * that is a deadlock even neither of B1 and A2 are waiting for anything.)
     515             :      */
     516         198 :     dlist_foreach(iter, &checkProc->lockGroupMembers)
     517             :     {
     518             :         PGPROC     *memberProc;
     519             : 
     520          92 :         memberProc = dlist_container(PGPROC, lockGroupLink, iter.cur);
     521             : 
     522          92 :         if (memberProc->links.next != NULL && memberProc->waitLock != NULL &&
     523          42 :             memberProc != checkProc &&
     524          42 :             FindLockCycleRecurseMember(memberProc, checkProc, depth, softEdges,
     525             :                                        nSoftEdges))
     526           8 :             return true;
     527             :     }
     528             : 
     529         106 :     return false;
     530             : }
     531             : 
     532             : static bool
     533         172 : FindLockCycleRecurseMember(PGPROC *checkProc,
     534             :                            PGPROC *checkProcLeader,
     535             :                            int depth,
     536             :                            EDGE *softEdges, /* output argument */
     537             :                            int *nSoftEdges) /* output argument */
     538             : {
     539             :     PGPROC     *proc;
     540         172 :     LOCK       *lock = checkProc->waitLock;
     541             :     dlist_iter  proclock_iter;
     542             :     LockMethod  lockMethodTable;
     543             :     int         conflictMask;
     544             :     int         i;
     545             :     int         numLockModes,
     546             :                 lm;
     547             : 
     548             :     /*
     549             :      * The relation extension lock can never participate in actual deadlock
     550             :      * cycle.  See Assert in LockAcquireExtended.  So, there is no advantage
     551             :      * in checking wait edges from it.
     552             :      */
     553         172 :     if (LOCK_LOCKTAG(*lock) == LOCKTAG_RELATION_EXTEND)
     554           0 :         return false;
     555             : 
     556         172 :     lockMethodTable = GetLocksMethodTable(lock);
     557         172 :     numLockModes = lockMethodTable->numLockModes;
     558         172 :     conflictMask = lockMethodTable->conflictTab[checkProc->waitLockMode];
     559             : 
     560             :     /*
     561             :      * Scan for procs that already hold conflicting locks.  These are "hard"
     562             :      * edges in the waits-for graph.
     563             :      */
     564         508 :     dlist_foreach(proclock_iter, &lock->procLocks)
     565             :     {
     566         408 :         PROCLOCK   *proclock = dlist_container(PROCLOCK, lockLink, proclock_iter.cur);
     567             :         PGPROC     *leader;
     568             : 
     569         408 :         proc = proclock->tag.myProc;
     570         408 :         leader = proc->lockGroupLeader == NULL ? proc : proc->lockGroupLeader;
     571             : 
     572             :         /* A proc never blocks itself or any other lock group member */
     573         408 :         if (leader != checkProcLeader)
     574             :         {
     575        2076 :             for (lm = 1; lm <= numLockModes; lm++)
     576             :             {
     577        1932 :                 if ((proclock->holdMask & LOCKBIT_ON(lm)) &&
     578             :                     (conflictMask & LOCKBIT_ON(lm)))
     579             :                 {
     580             :                     /* This proc hard-blocks checkProc */
     581         120 :                     if (FindLockCycleRecurse(proc, depth + 1,
     582             :                                              softEdges, nSoftEdges))
     583             :                     {
     584             :                         /* fill deadlockDetails[] */
     585          72 :                         DEADLOCK_INFO *info = &deadlockDetails[depth];
     586             : 
     587          72 :                         info->locktag = lock->tag;
     588          72 :                         info->lockmode = checkProc->waitLockMode;
     589          72 :                         info->pid = checkProc->pid;
     590             : 
     591          72 :                         return true;
     592             :                     }
     593             : 
     594             :                     /*
     595             :                      * No deadlock here, but see if this proc is an autovacuum
     596             :                      * that is directly hard-blocking our own proc.  If so,
     597             :                      * report it so that the caller can send a cancel signal
     598             :                      * to it, if appropriate.  If there's more than one such
     599             :                      * proc, it's indeterminate which one will be reported.
     600             :                      *
     601             :                      * We don't touch autovacuums that are indirectly blocking
     602             :                      * us; it's up to the direct blockee to take action.  This
     603             :                      * rule simplifies understanding the behavior and ensures
     604             :                      * that an autovacuum won't be canceled with less than
     605             :                      * deadlock_timeout grace period.
     606             :                      *
     607             :                      * Note we read statusFlags without any locking.  This is
     608             :                      * OK only for checking the PROC_IS_AUTOVACUUM flag,
     609             :                      * because that flag is set at process start and never
     610             :                      * reset.  There is logic elsewhere to avoid canceling an
     611             :                      * autovacuum that is working to prevent XID wraparound
     612             :                      * problems (which needs to read a different statusFlags
     613             :                      * bit), but we don't do that here to avoid grabbing
     614             :                      * ProcArrayLock.
     615             :                      */
     616          48 :                     if (checkProc == MyProc &&
     617          28 :                         proc->statusFlags & PROC_IS_AUTOVACUUM)
     618           0 :                         blocking_autovacuum_proc = proc;
     619             : 
     620             :                     /* We're done looking at this proclock */
     621          48 :                     break;
     622             :                 }
     623             :             }
     624             :         }
     625             :     }
     626             : 
     627             :     /*
     628             :      * Scan for procs that are ahead of this one in the lock's wait queue.
     629             :      * Those that have conflicting requests soft-block this one.  This must be
     630             :      * done after the hard-block search, since if another proc both hard- and
     631             :      * soft-blocks this one, we want to call it a hard edge.
     632             :      *
     633             :      * If there is a proposed re-ordering of the lock's wait order, use that
     634             :      * rather than the current wait order.
     635             :      */
     636         118 :     for (i = 0; i < nWaitOrders; i++)
     637             :     {
     638          54 :         if (waitOrders[i].lock == lock)
     639          36 :             break;
     640             :     }
     641             : 
     642         100 :     if (i < nWaitOrders)
     643             :     {
     644             :         /* Use the given hypothetical wait queue order */
     645          36 :         PGPROC    **procs = waitOrders[i].procs;
     646          36 :         int         queue_size = waitOrders[i].nProcs;
     647             : 
     648          46 :         for (i = 0; i < queue_size; i++)
     649             :         {
     650             :             PGPROC     *leader;
     651             : 
     652          46 :             proc = procs[i];
     653          46 :             leader = proc->lockGroupLeader == NULL ? proc :
     654             :                 proc->lockGroupLeader;
     655             : 
     656             :             /*
     657             :              * TopoSort will always return an ordering with group members
     658             :              * adjacent to each other in the wait queue (see comments
     659             :              * therein). So, as soon as we reach a process in the same lock
     660             :              * group as checkProc, we know we've found all the conflicts that
     661             :              * precede any member of the lock group lead by checkProcLeader.
     662             :              */
     663          46 :             if (leader == checkProcLeader)
     664          36 :                 break;
     665             : 
     666             :             /* Is there a conflict with this guy's request? */
     667          10 :             if ((LOCKBIT_ON(proc->waitLockMode) & conflictMask) != 0)
     668             :             {
     669             :                 /* This proc soft-blocks checkProc */
     670          10 :                 if (FindLockCycleRecurse(proc, depth + 1,
     671             :                                          softEdges, nSoftEdges))
     672             :                 {
     673             :                     /* fill deadlockDetails[] */
     674           0 :                     DEADLOCK_INFO *info = &deadlockDetails[depth];
     675             : 
     676           0 :                     info->locktag = lock->tag;
     677           0 :                     info->lockmode = checkProc->waitLockMode;
     678           0 :                     info->pid = checkProc->pid;
     679             : 
     680             :                     /*
     681             :                      * Add this edge to the list of soft edges in the cycle
     682             :                      */
     683             :                     Assert(*nSoftEdges < MaxBackends);
     684           0 :                     softEdges[*nSoftEdges].waiter = checkProcLeader;
     685           0 :                     softEdges[*nSoftEdges].blocker = leader;
     686           0 :                     softEdges[*nSoftEdges].lock = lock;
     687           0 :                     (*nSoftEdges)++;
     688           0 :                     return true;
     689             :                 }
     690             :             }
     691             :         }
     692             :     }
     693             :     else
     694             :     {
     695          64 :         PGPROC     *lastGroupMember = NULL;
     696             :         dlist_iter  proc_iter;
     697             :         dclist_head *waitQueue;
     698             : 
     699             :         /* Use the true lock wait queue order */
     700          64 :         waitQueue = &lock->waitProcs;
     701             : 
     702             :         /*
     703             :          * Find the last member of the lock group that is present in the wait
     704             :          * queue.  Anything after this is not a soft lock conflict. If group
     705             :          * locking is not in use, then we know immediately which process we're
     706             :          * looking for, but otherwise we've got to search the wait queue to
     707             :          * find the last process actually present.
     708             :          */
     709          64 :         if (checkProc->lockGroupLeader == NULL)
     710          46 :             lastGroupMember = checkProc;
     711             :         else
     712             :         {
     713          64 :             dclist_foreach(proc_iter, waitQueue)
     714             :             {
     715          46 :                 proc = dlist_container(PGPROC, links, proc_iter.cur);
     716             : 
     717          46 :                 if (proc->lockGroupLeader == checkProcLeader)
     718          26 :                     lastGroupMember = proc;
     719             :             }
     720             :             Assert(lastGroupMember != NULL);
     721             :         }
     722             : 
     723             :         /*
     724             :          * OK, now rescan (or scan) the queue to identify the soft conflicts.
     725             :          */
     726          86 :         dclist_foreach(proc_iter, waitQueue)
     727             :         {
     728             :             PGPROC     *leader;
     729             : 
     730          86 :             proc = dlist_container(PGPROC, links, proc_iter.cur);
     731             : 
     732          86 :             leader = proc->lockGroupLeader == NULL ? proc :
     733             :                 proc->lockGroupLeader;
     734             : 
     735             :             /* Done when we reach the target proc */
     736          86 :             if (proc == lastGroupMember)
     737          54 :                 break;
     738             : 
     739             :             /* Is there a conflict with this guy's request? */
     740          32 :             if ((LOCKBIT_ON(proc->waitLockMode) & conflictMask) != 0 &&
     741             :                 leader != checkProcLeader)
     742             :             {
     743             :                 /* This proc soft-blocks checkProc */
     744          22 :                 if (FindLockCycleRecurse(proc, depth + 1,
     745             :                                          softEdges, nSoftEdges))
     746             :                 {
     747             :                     /* fill deadlockDetails[] */
     748          10 :                     DEADLOCK_INFO *info = &deadlockDetails[depth];
     749             : 
     750          10 :                     info->locktag = lock->tag;
     751          10 :                     info->lockmode = checkProc->waitLockMode;
     752          10 :                     info->pid = checkProc->pid;
     753             : 
     754             :                     /*
     755             :                      * Add this edge to the list of soft edges in the cycle
     756             :                      */
     757             :                     Assert(*nSoftEdges < MaxBackends);
     758          10 :                     softEdges[*nSoftEdges].waiter = checkProcLeader;
     759          10 :                     softEdges[*nSoftEdges].blocker = leader;
     760          10 :                     softEdges[*nSoftEdges].lock = lock;
     761          10 :                     (*nSoftEdges)++;
     762          10 :                     return true;
     763             :                 }
     764             :             }
     765             :         }
     766             :     }
     767             : 
     768             :     /*
     769             :      * No conflict detected here.
     770             :      */
     771          90 :     return false;
     772             : }
     773             : 
     774             : 
     775             : /*
     776             :  * ExpandConstraints -- expand a list of constraints into a set of
     777             :  *      specific new orderings for affected wait queues
     778             :  *
     779             :  * Input is a list of soft edges to be reversed.  The output is a list
     780             :  * of nWaitOrders WAIT_ORDER structs in waitOrders[], with PGPROC array
     781             :  * workspace in waitOrderProcs[].
     782             :  *
     783             :  * Returns true if able to build an ordering that satisfies all the
     784             :  * constraints, false if not (there are contradictory constraints).
     785             :  */
     786             : static bool
     787          50 : ExpandConstraints(EDGE *constraints,
     788             :                   int nConstraints)
     789             : {
     790          50 :     int         nWaitOrderProcs = 0;
     791             :     int         i,
     792             :                 j;
     793             : 
     794          50 :     nWaitOrders = 0;
     795             : 
     796             :     /*
     797             :      * Scan constraint list backwards.  This is because the last-added
     798             :      * constraint is the only one that could fail, and so we want to test it
     799             :      * for inconsistency first.
     800             :      */
     801          56 :     for (i = nConstraints; --i >= 0;)
     802             :     {
     803           6 :         LOCK       *lock = constraints[i].lock;
     804             : 
     805             :         /* Did we already make a list for this lock? */
     806           6 :         for (j = nWaitOrders; --j >= 0;)
     807             :         {
     808           0 :             if (waitOrders[j].lock == lock)
     809           0 :                 break;
     810             :         }
     811           6 :         if (j >= 0)
     812           0 :             continue;
     813             :         /* No, so allocate a new list */
     814           6 :         waitOrders[nWaitOrders].lock = lock;
     815           6 :         waitOrders[nWaitOrders].procs = waitOrderProcs + nWaitOrderProcs;
     816           6 :         waitOrders[nWaitOrders].nProcs = dclist_count(&lock->waitProcs);
     817           6 :         nWaitOrderProcs += dclist_count(&lock->waitProcs);
     818             :         Assert(nWaitOrderProcs <= MaxBackends);
     819             : 
     820             :         /*
     821             :          * Do the topo sort.  TopoSort need not examine constraints after this
     822             :          * one, since they must be for different locks.
     823             :          */
     824           6 :         if (!TopoSort(lock, constraints, i + 1,
     825           6 :                       waitOrders[nWaitOrders].procs))
     826           0 :             return false;
     827           6 :         nWaitOrders++;
     828             :     }
     829          50 :     return true;
     830             : }
     831             : 
     832             : 
     833             : /*
     834             :  * TopoSort -- topological sort of a wait queue
     835             :  *
     836             :  * Generate a re-ordering of a lock's wait queue that satisfies given
     837             :  * constraints about certain procs preceding others.  (Each such constraint
     838             :  * is a fact of a partial ordering.)  Minimize rearrangement of the queue
     839             :  * not needed to achieve the partial ordering.
     840             :  *
     841             :  * This is a lot simpler and slower than, for example, the topological sort
     842             :  * algorithm shown in Knuth's Volume 1.  However, Knuth's method doesn't
     843             :  * try to minimize the damage to the existing order.  In practice we are
     844             :  * not likely to be working with more than a few constraints, so the apparent
     845             :  * slowness of the algorithm won't really matter.
     846             :  *
     847             :  * The initial queue ordering is taken directly from the lock's wait queue.
     848             :  * The output is an array of PGPROC pointers, of length equal to the lock's
     849             :  * wait queue length (the caller is responsible for providing this space).
     850             :  * The partial order is specified by an array of EDGE structs.  Each EDGE
     851             :  * is one that we need to reverse, therefore the "waiter" must appear before
     852             :  * the "blocker" in the output array.  The EDGE array may well contain
     853             :  * edges associated with other locks; these should be ignored.
     854             :  *
     855             :  * Returns true if able to build an ordering that satisfies all the
     856             :  * constraints, false if not (there are contradictory constraints).
     857             :  */
     858             : static bool
     859           6 : TopoSort(LOCK *lock,
     860             :          EDGE *constraints,
     861             :          int nConstraints,
     862             :          PGPROC **ordering)     /* output argument */
     863             : {
     864           6 :     dclist_head *waitQueue = &lock->waitProcs;
     865           6 :     int         queue_size = dclist_count(waitQueue);
     866             :     PGPROC     *proc;
     867             :     int         i,
     868             :                 j,
     869             :                 jj,
     870             :                 k,
     871             :                 kk,
     872             :                 last;
     873             :     dlist_iter  proc_iter;
     874             : 
     875             :     /* First, fill topoProcs[] array with the procs in their current order */
     876           6 :     i = 0;
     877          24 :     dclist_foreach(proc_iter, waitQueue)
     878             :     {
     879          18 :         proc = dlist_container(PGPROC, links, proc_iter.cur);
     880          18 :         topoProcs[i++] = proc;
     881             :     }
     882             :     Assert(i == queue_size);
     883             : 
     884             :     /*
     885             :      * Scan the constraints, and for each proc in the array, generate a count
     886             :      * of the number of constraints that say it must be before something else,
     887             :      * plus a list of the constraints that say it must be after something
     888             :      * else. The count for the j'th proc is stored in beforeConstraints[j],
     889             :      * and the head of its list in afterConstraints[j].  Each constraint
     890             :      * stores its list link in constraints[i].link (note any constraint will
     891             :      * be in just one list). The array index for the before-proc of the i'th
     892             :      * constraint is remembered in constraints[i].pred.
     893             :      *
     894             :      * Note that it's not necessarily the case that every constraint affects
     895             :      * this particular wait queue.  Prior to group locking, a process could be
     896             :      * waiting for at most one lock.  But a lock group can be waiting for
     897             :      * zero, one, or multiple locks.  Since topoProcs[] is an array of the
     898             :      * processes actually waiting, while constraints[] is an array of group
     899             :      * leaders, we've got to scan through topoProcs[] for each constraint,
     900             :      * checking whether both a waiter and a blocker for that group are
     901             :      * present.  If so, the constraint is relevant to this wait queue; if not,
     902             :      * it isn't.
     903             :      */
     904          12 :     MemSet(beforeConstraints, 0, queue_size * sizeof(int));
     905          12 :     MemSet(afterConstraints, 0, queue_size * sizeof(int));
     906          12 :     for (i = 0; i < nConstraints; i++)
     907             :     {
     908             :         /*
     909             :          * Find a representative process that is on the lock queue and part of
     910             :          * the waiting lock group.  This may or may not be the leader, which
     911             :          * may or may not be waiting at all.  If there are any other processes
     912             :          * in the same lock group on the queue, set their number of
     913             :          * beforeConstraints to -1 to indicate that they should be emitted
     914             :          * with their groupmates rather than considered separately.
     915             :          *
     916             :          * In this loop and the similar one just below, it's critical that we
     917             :          * consistently select the same representative member of any one lock
     918             :          * group, so that all the constraints are associated with the same
     919             :          * proc, and the -1's are only associated with not-representative
     920             :          * members.  We select the last one in the topoProcs array.
     921             :          */
     922           6 :         proc = constraints[i].waiter;
     923             :         Assert(proc != NULL);
     924           6 :         jj = -1;
     925          24 :         for (j = queue_size; --j >= 0;)
     926             :         {
     927          18 :             PGPROC     *waiter = topoProcs[j];
     928             : 
     929          18 :             if (waiter == proc || waiter->lockGroupLeader == proc)
     930             :             {
     931             :                 Assert(waiter->waitLock == lock);
     932          10 :                 if (jj == -1)
     933           6 :                     jj = j;
     934             :                 else
     935             :                 {
     936             :                     Assert(beforeConstraints[j] <= 0);
     937           4 :                     beforeConstraints[j] = -1;
     938             :                 }
     939             :             }
     940             :         }
     941             : 
     942             :         /* If no matching waiter, constraint is not relevant to this lock. */
     943           6 :         if (jj < 0)
     944           0 :             continue;
     945             : 
     946             :         /*
     947             :          * Similarly, find a representative process that is on the lock queue
     948             :          * and waiting for the blocking lock group.  Again, this could be the
     949             :          * leader but does not need to be.
     950             :          */
     951           6 :         proc = constraints[i].blocker;
     952             :         Assert(proc != NULL);
     953           6 :         kk = -1;
     954          24 :         for (k = queue_size; --k >= 0;)
     955             :         {
     956          18 :             PGPROC     *blocker = topoProcs[k];
     957             : 
     958          18 :             if (blocker == proc || blocker->lockGroupLeader == proc)
     959             :             {
     960             :                 Assert(blocker->waitLock == lock);
     961           6 :                 if (kk == -1)
     962           6 :                     kk = k;
     963             :                 else
     964             :                 {
     965             :                     Assert(beforeConstraints[k] <= 0);
     966           0 :                     beforeConstraints[k] = -1;
     967             :                 }
     968             :             }
     969             :         }
     970             : 
     971             :         /* If no matching blocker, constraint is not relevant to this lock. */
     972           6 :         if (kk < 0)
     973           0 :             continue;
     974             : 
     975             :         Assert(beforeConstraints[jj] >= 0);
     976           6 :         beforeConstraints[jj]++;    /* waiter must come before */
     977             :         /* add this constraint to list of after-constraints for blocker */
     978           6 :         constraints[i].pred = jj;
     979           6 :         constraints[i].link = afterConstraints[kk];
     980           6 :         afterConstraints[kk] = i + 1;
     981             :     }
     982             : 
     983             :     /*--------------------
     984             :      * Now scan the topoProcs array backwards.  At each step, output the
     985             :      * last proc that has no remaining before-constraints plus any other
     986             :      * members of the same lock group; then decrease the beforeConstraints
     987             :      * count of each of the procs it was constrained against.
     988             :      * i = index of ordering[] entry we want to output this time
     989             :      * j = search index for topoProcs[]
     990             :      * k = temp for scanning constraint list for proc j
     991             :      * last = last non-null index in topoProcs (avoid redundant searches)
     992             :      *--------------------
     993             :      */
     994           6 :     last = queue_size - 1;
     995          20 :     for (i = queue_size - 1; i >= 0;)
     996             :     {
     997             :         int         c;
     998          14 :         int         nmatches = 0;
     999             : 
    1000             :         /* Find next candidate to output */
    1001          14 :         while (topoProcs[last] == NULL)
    1002           0 :             last--;
    1003          28 :         for (j = last; j >= 0; j--)
    1004             :         {
    1005          28 :             if (topoProcs[j] != NULL && beforeConstraints[j] == 0)
    1006          14 :                 break;
    1007             :         }
    1008             : 
    1009             :         /* If no available candidate, topological sort fails */
    1010          14 :         if (j < 0)
    1011           0 :             return false;
    1012             : 
    1013             :         /*
    1014             :          * Output everything in the lock group.  There's no point in
    1015             :          * outputting an ordering where members of the same lock group are not
    1016             :          * consecutive on the wait queue: if some other waiter is between two
    1017             :          * requests that belong to the same group, then either it conflicts
    1018             :          * with both of them and is certainly not a solution; or it conflicts
    1019             :          * with at most one of them and is thus isomorphic to an ordering
    1020             :          * where the group members are consecutive.
    1021             :          */
    1022          14 :         proc = topoProcs[j];
    1023          14 :         if (proc->lockGroupLeader != NULL)
    1024           4 :             proc = proc->lockGroupLeader;
    1025             :         Assert(proc != NULL);
    1026          56 :         for (c = 0; c <= last; ++c)
    1027             :         {
    1028          42 :             if (topoProcs[c] == proc || (topoProcs[c] != NULL &&
    1029          22 :                                          topoProcs[c]->lockGroupLeader == proc))
    1030             :             {
    1031          18 :                 ordering[i - nmatches] = topoProcs[c];
    1032          18 :                 topoProcs[c] = NULL;
    1033          18 :                 ++nmatches;
    1034             :             }
    1035             :         }
    1036             :         Assert(nmatches > 0);
    1037          14 :         i -= nmatches;
    1038             : 
    1039             :         /* Update beforeConstraints counts of its predecessors */
    1040          20 :         for (k = afterConstraints[j]; k > 0; k = constraints[k - 1].link)
    1041           6 :             beforeConstraints[constraints[k - 1].pred]--;
    1042             :     }
    1043             : 
    1044             :     /* Done */
    1045           6 :     return true;
    1046             : }
    1047             : 
    1048             : #ifdef DEBUG_DEADLOCK
    1049             : static void
    1050             : PrintLockQueue(LOCK *lock, const char *info)
    1051             : {
    1052             :     dclist_head *waitQueue = &lock->waitProcs;
    1053             :     dlist_iter  proc_iter;
    1054             : 
    1055             :     printf("%s lock %p queue ", info, lock);
    1056             : 
    1057             :     dclist_foreach(proc_iter, waitQueue)
    1058             :     {
    1059             :         PGPROC     *proc = dlist_container(PGPROC, links, proc_iter.cur);
    1060             : 
    1061             :         printf(" %d", proc->pid);
    1062             :     }
    1063             :     printf("\n");
    1064             :     fflush(stdout);
    1065             : }
    1066             : #endif
    1067             : 
    1068             : /*
    1069             :  * Report a detected deadlock, with available details.
    1070             :  */
    1071             : void
    1072          10 : DeadLockReport(void)
    1073             : {
    1074             :     StringInfoData clientbuf;   /* errdetail for client */
    1075             :     StringInfoData logbuf;      /* errdetail for server log */
    1076             :     StringInfoData locktagbuf;
    1077             :     int         i;
    1078             : 
    1079          10 :     initStringInfo(&clientbuf);
    1080          10 :     initStringInfo(&logbuf);
    1081          10 :     initStringInfo(&locktagbuf);
    1082             : 
    1083             :     /* Generate the "waits for" lines sent to the client */
    1084          44 :     for (i = 0; i < nDeadlockDetails; i++)
    1085             :     {
    1086          34 :         DEADLOCK_INFO *info = &deadlockDetails[i];
    1087             :         int         nextpid;
    1088             : 
    1089             :         /* The last proc waits for the first one... */
    1090          34 :         if (i < nDeadlockDetails - 1)
    1091          24 :             nextpid = info[1].pid;
    1092             :         else
    1093          10 :             nextpid = deadlockDetails[0].pid;
    1094             : 
    1095             :         /* reset locktagbuf to hold next object description */
    1096          34 :         resetStringInfo(&locktagbuf);
    1097             : 
    1098          34 :         DescribeLockTag(&locktagbuf, &info->locktag);
    1099             : 
    1100          34 :         if (i > 0)
    1101          24 :             appendStringInfoChar(&clientbuf, '\n');
    1102             : 
    1103          68 :         appendStringInfo(&clientbuf,
    1104          34 :                          _("Process %d waits for %s on %s; blocked by process %d."),
    1105             :                          info->pid,
    1106          34 :                          GetLockmodeName(info->locktag.locktag_lockmethodid,
    1107             :                                          info->lockmode),
    1108             :                          locktagbuf.data,
    1109             :                          nextpid);
    1110             :     }
    1111             : 
    1112             :     /* Duplicate all the above for the server ... */
    1113          10 :     appendBinaryStringInfo(&logbuf, clientbuf.data, clientbuf.len);
    1114             : 
    1115             :     /* ... and add info about query strings */
    1116          44 :     for (i = 0; i < nDeadlockDetails; i++)
    1117             :     {
    1118          34 :         DEADLOCK_INFO *info = &deadlockDetails[i];
    1119             : 
    1120          34 :         appendStringInfoChar(&logbuf, '\n');
    1121             : 
    1122          34 :         appendStringInfo(&logbuf,
    1123          34 :                          _("Process %d: %s"),
    1124             :                          info->pid,
    1125             :                          pgstat_get_backend_current_activity(info->pid, false));
    1126             :     }
    1127             : 
    1128          10 :     pgstat_report_deadlock();
    1129             : 
    1130          10 :     ereport(ERROR,
    1131             :             (errcode(ERRCODE_T_R_DEADLOCK_DETECTED),
    1132             :              errmsg("deadlock detected"),
    1133             :              errdetail_internal("%s", clientbuf.data),
    1134             :              errdetail_log("%s", logbuf.data),
    1135             :              errhint("See server log for query details.")));
    1136             : }
    1137             : 
    1138             : /*
    1139             :  * RememberSimpleDeadLock: set up info for DeadLockReport when ProcSleep
    1140             :  * detects a trivial (two-way) deadlock.  proc1 wants to block for lockmode
    1141             :  * on lock, but proc2 is already waiting and would be blocked by proc1.
    1142             :  */
    1143             : void
    1144           2 : RememberSimpleDeadLock(PGPROC *proc1,
    1145             :                        LOCKMODE lockmode,
    1146             :                        LOCK *lock,
    1147             :                        PGPROC *proc2)
    1148             : {
    1149           2 :     DEADLOCK_INFO *info = &deadlockDetails[0];
    1150             : 
    1151           2 :     info->locktag = lock->tag;
    1152           2 :     info->lockmode = lockmode;
    1153           2 :     info->pid = proc1->pid;
    1154           2 :     info++;
    1155           2 :     info->locktag = proc2->waitLock->tag;
    1156           2 :     info->lockmode = proc2->waitLockMode;
    1157           2 :     info->pid = proc2->pid;
    1158           2 :     nDeadlockDetails = 2;
    1159           2 : }

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