1 /*-------------------------------------------------------------------------
4 * routines to manage per-process shared memory data structure
6 * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
7 * Portions Copyright (c) 1994, Regents of the University of California
11 * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.69 2000/02/22 09:55:20 inoue Exp $
13 *-------------------------------------------------------------------------
16 * Each postgres backend gets one of these. We'll use it to
17 * clean up after the process should the process suddenly die.
21 * ProcSleep(), ProcWakeup(), ProcWakeupNext(),
22 * ProcQueueAlloc() -- create a shm queue for sleeping processes
23 * ProcQueueInit() -- create a queue without allocing memory
25 * Locking and waiting for buffers can cause the backend to be
26 * put to sleep. Whoever releases the lock, etc. wakes the
27 * process up again (and gives it an error code so it knows
28 * whether it was awoken on an error condition).
32 * ProcReleaseLocks -- frees the locks associated with this process,
33 * ProcKill -- destroys the shared memory state (and locks)
34 * associated with the process.
36 * 5/15/91 -- removed the buffer pool based lock chain in favor
37 * of a shared memory lock chain. The write-protection is
38 * more expensive if the lock chain is in the buffer pool.
39 * The only reason I kept the lock chain in the buffer pool
40 * in the first place was to allow the lock table to grow larger
41 * than available shared memory and that isn't going to work
42 * without a lot of unimplemented support anyway.
44 * 4/7/95 -- instead of allocating a set of 1 semaphore per process, we
45 * allocate a semaphore from a set of PROC_NSEMS_PER_SET semaphores
46 * shared among backends (we keep a few sets of semaphores around).
47 * This is so that we can support more backends. (system-wide semaphore
48 * sets run out pretty fast.) -ay 4/95
50 * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.69 2000/02/22 09:55:20 inoue Exp $
55 #include <sys/types.h>
57 #if defined(solaris_sparc) || defined(__CYGWIN__)
63 #include "miscadmin.h"
64 #include "libpq/pqsignal.h"
67 #include "storage/ipc.h"
68 /* In Ultrix and QNX, sem.h must be included after ipc.h */
71 #include "storage/lmgr.h"
72 #include "storage/proc.h"
73 #include "utils/trace.h"
75 void HandleDeadLock(SIGNAL_ARGS);
76 static void ProcFreeAllSemaphores(void);
77 static bool GetOffWaitqueue(PROC *);
79 #define DeadlockCheckTimer pg_options[OPT_DEADLOCKTIMEOUT]
81 /* --------------------
82 * Spin lock for manipulating the shared process data structure:
83 * ProcGlobal.... Adding an extra spin lock seemed like the smallest
84 * hack to get around reading and updating this structure in shared
85 * memory. -mer 17 July 1991
86 * --------------------
88 SPINLOCK ProcStructLock;
90 static PROC_HDR *ProcGlobal = NULL;
94 static void ProcKill(int exitStatus, int pid);
95 static void ProcGetNewSemKeyAndNum(IPCKey *key, int *semNum);
96 static void ProcFreeSem(IpcSemaphoreKey semKey, int semNum);
98 static char *DeadLockMessage = "Deadlock detected -- See the lock(l) manual page for a possible cause.";
102 * initializes the global process table. We put it here so that
103 * the postmaster can do this initialization. (ProcFreeAllSemaphores needs
104 * to read this table on exiting the postmaster. If we have the first
105 * backend do this, starting up and killing the postmaster without
106 * starting any backends will be a problem.)
108 * We also allocate all the per-process semaphores we will need to support
109 * the requested number of backends. We used to allocate semaphores
110 * only when backends were actually started up, but that is bad because
111 * it lets Postgres fail under load --- a lot of Unix systems are
112 * (mis)configured with small limits on the number of semaphores, and
113 * running out when trying to start another backend is a common failure.
114 * So, now we grab enough semaphores to support the desired max number
115 * of backends immediately at initialization --- if the sysadmin has set
116 * MaxBackends higher than his kernel will support, he'll find out sooner
120 InitProcGlobal(IPCKey key, int maxBackends)
124 /* attach to the free list */
125 ProcGlobal = (PROC_HDR *)
126 ShmemInitStruct("Proc Header", (unsigned) sizeof(PROC_HDR), &found);
128 /* --------------------
129 * We're the first - initialize.
130 * XXX if found should ever be true, it is a sign of impending doom ...
131 * ought to complain if so?
132 * --------------------
138 ProcGlobal->freeProcs = INVALID_OFFSET;
139 ProcGlobal->currKey = IPCGetProcessSemaphoreInitKey(key);
140 for (i = 0; i < MAX_PROC_SEMS / PROC_NSEMS_PER_SET; i++)
141 ProcGlobal->freeSemMap[i] = 0;
144 * Arrange to delete semas on exit --- set this up now so that we
145 * will clean up if pre-allocation fails...
147 on_shmem_exit(ProcFreeAllSemaphores, NULL);
150 * Pre-create the semaphores for the first maxBackends processes,
151 * unless we are running as a standalone backend.
153 if (key != PrivateIPCKey)
156 i < (maxBackends + PROC_NSEMS_PER_SET - 1) / PROC_NSEMS_PER_SET;
159 IPCKey semKey = ProcGlobal->currKey + i;
162 semId = IpcSemaphoreCreate(semKey,
165 IpcSemaphoreDefaultStartValue,
168 elog(FATAL, "InitProcGlobal: IpcSemaphoreCreate failed");
169 /* mark this sema set allocated */
170 ProcGlobal->freeSemMap[i] = (1 << PROC_NSEMS_PER_SET);
176 /* ------------------------
177 * InitProc -- create a per-process data structure for this process
178 * used by the lock manager on semaphore queues.
179 * ------------------------
182 InitProcess(IPCKey key)
185 unsigned long location,
188 SpinAcquire(ProcStructLock);
190 /* attach to the free list */
191 ProcGlobal = (PROC_HDR *)
192 ShmemInitStruct("Proc Header", (unsigned) sizeof(PROC_HDR), &found);
195 /* this should not happen. InitProcGlobal() is called before this. */
196 elog(STOP, "InitProcess: Proc Header uninitialized");
201 SpinRelease(ProcStructLock);
202 elog(ERROR, "ProcInit: you already exist");
206 /* try to get a proc from the free list first */
208 myOffset = ProcGlobal->freeProcs;
210 if (myOffset != INVALID_OFFSET)
212 MyProc = (PROC *) MAKE_PTR(myOffset);
213 ProcGlobal->freeProcs = MyProc->links.next;
219 * have to allocate one. We can't use the normal shmem index
220 * table mechanism because the proc structure is stored by PID
221 * instead of by a global name (need to look it up by PID when we
222 * cleanup dead processes).
225 MyProc = (PROC *) ShmemAlloc((unsigned) sizeof(PROC));
228 SpinRelease(ProcStructLock);
229 elog(FATAL, "cannot create new proc: out of memory");
232 /* this cannot be initialized until after the buffer pool */
233 SHMQueueInit(&(MyProc->lockQueue));
237 * zero out the spin lock counts and set the sLocks field for
238 * ProcStructLock to 1 as we have acquired this spinlock above but
239 * didn't record it since we didn't have MyProc until now.
241 MemSet(MyProc->sLocks, 0, sizeof(MyProc->sLocks));
242 MyProc->sLocks[ProcStructLock] = 1;
245 if (IsUnderPostmaster)
252 ProcGetNewSemKeyAndNum(&semKey, &semNum);
255 * Note: because of the pre-allocation done in InitProcGlobal,
256 * this call should always attach to an existing semaphore. It
257 * will (try to) create a new group of semaphores only if the
258 * postmaster tries to start more backends than it said it would.
260 semId = IpcSemaphoreCreate(semKey,
263 IpcSemaphoreDefaultStartValue,
267 * we might be reusing a semaphore that belongs to a dead backend.
268 * So be careful and reinitialize its value here.
270 semun.val = IpcSemaphoreDefaultStartValue;
271 semctl(semId, semNum, SETVAL, semun);
273 IpcSemaphoreLock(semId, semNum, IpcExclusiveLock);
274 MyProc->sem.semId = semId;
275 MyProc->sem.semNum = semNum;
276 MyProc->sem.semKey = semKey;
279 MyProc->sem.semId = -1;
281 /* ----------------------
283 * ----------------------
285 SpinRelease(ProcStructLock);
287 MyProc->pid = MyProcPid;
288 MyProc->databaseId = MyDatabaseId;
289 MyProc->xid = InvalidTransactionId;
290 MyProc->xmin = InvalidTransactionId;
293 * Start keeping spin lock stats from here on. Any botch before
294 * this initialization is forever botched
297 MemSet(MyProc->sLocks, 0, MAX_SPINS * sizeof(*MyProc->sLocks));
299 /* -------------------------
300 * Install ourselves in the shmem index table. The name to
301 * use is determined by the OS-assigned process id. That
302 * allows the cleanup process to find us after any untimely
304 * -------------------------
306 location = MAKE_OFFSET(MyProc);
307 if ((!ShmemPIDLookup(MyProcPid, &location)) || (location != MAKE_OFFSET(MyProc)))
308 elog(STOP, "InitProc: ShmemPID table broken");
310 MyProc->errType = NO_ERROR;
311 SHMQueueElemInit(&(MyProc->links));
313 on_shmem_exit(ProcKill, (caddr_t) MyProcPid);
316 /* -----------------------
317 * get off the wait queue
318 * -----------------------
321 GetOffWaitqueue(PROC *proc)
323 bool getoffed = false;
325 if (proc->links.next != INVALID_OFFSET)
327 int lockmode = proc->token;
328 Assert(proc->waitLock->waitProcs.size > 0);
329 SHMQueueDelete(&(proc->links));
330 --proc->waitLock->waitProcs.size;
331 Assert(proc->waitLock->nHolding > 0);
332 Assert(proc->waitLock->nHolding > proc->waitLock->nActive);
333 --proc->waitLock->nHolding;
334 Assert(proc->waitLock->holders[lockmode] > 0);
335 --proc->waitLock->holders[lockmode];
336 if (proc->waitLock->activeHolders[lockmode] ==
337 proc->waitLock->holders[lockmode])
338 proc->waitLock->waitMask &= ~(1 << lockmode);
341 SHMQueueElemInit(&(proc->links));
347 * ProcReleaseLocks() -- release all locks associated with this process
355 LockReleaseAll(1, &MyProc->lockQueue);
356 GetOffWaitqueue(MyProc);
361 * used by the postmaster to clean up the global tables. This also frees
362 * up the semaphore used for the lmgr of the process. (We have to do
363 * this is the postmaster instead of doing a IpcSemaphoreKill on exiting
364 * the process because the semaphore set is shared among backends and
365 * we don't want to remove other's semaphores on exit.)
370 SHMEM_OFFSET location;
373 location = INVALID_OFFSET;
375 location = ShmemPIDDestroy(pid);
376 if (location == INVALID_OFFSET)
378 proc = (PROC *) MAKE_PTR(location);
380 SpinAcquire(ProcStructLock);
382 ProcFreeSem(proc->sem.semKey, proc->sem.semNum);
384 proc->links.next = ProcGlobal->freeProcs;
385 ProcGlobal->freeProcs = MAKE_OFFSET(proc);
387 SpinRelease(ProcStructLock);
393 * ProcKill() -- Destroy the per-proc data structure for
394 * this process. Release any of its held spin locks.
397 ProcKill(int exitStatus, int pid)
400 SHMEM_OFFSET location;
402 /* --------------------
403 * If this is a FATAL exit the postmaster will have to kill all the
404 * existing backends and reinitialize shared memory. So all we don't
405 * need to do anything here.
406 * --------------------
411 ShmemPIDLookup(MyProcPid, &location);
412 if (location == INVALID_OFFSET)
415 proc = (PROC *) MAKE_PTR(location);
417 Assert(proc == MyProc || pid != MyProcPid);
422 * Assume one lock table.
425 ProcReleaseSpins(proc);
426 LockReleaseAll(DEFAULT_LOCKMETHOD, &proc->lockQueue);
431 * Assume we have a second lock table.
433 LockReleaseAll(USER_LOCKMETHOD, &proc->lockQueue);
437 * get off the wait queue
440 GetOffWaitqueue(proc);
446 * ProcQueue package: routines for putting processes to sleep
451 * ProcQueueAlloc -- alloc/attach to a shared memory process queue
453 * Returns: a pointer to the queue or NULL
454 * Side Effects: Initializes the queue if we allocated one
458 ProcQueueAlloc(char *name)
461 PROC_QUEUE *queue = (PROC_QUEUE *)
462 ShmemInitStruct(name, (unsigned) sizeof(PROC_QUEUE), &found);
467 ProcQueueInit(queue);
474 * ProcQueueInit -- initialize a shared memory process queue
477 ProcQueueInit(PROC_QUEUE *queue)
479 SHMQueueInit(&(queue->links));
484 static bool lockWaiting = false;
485 void SetWaitingForLock(bool waiting)
487 lockWaiting = waiting;
489 void LockWaitCancel(void)
491 struct itimerval timeval, dummy;
493 if (!lockWaiting) return;
495 /* Deadlock timer off */
496 MemSet(&timeval, 0, sizeof(struct itimerval));
497 setitimer(ITIMER_REAL, &timeval, &dummy);
498 if (GetOffWaitqueue(MyProc))
499 elog(ERROR, "Query cancel requested while waiting lock");
503 * ProcSleep -- put a process to sleep
505 * P() on the semaphore should put us to sleep. The process
506 * semaphore is cleared by default, so the first time we try
507 * to acquire it, we sleep.
509 * ASSUME: that no one will fiddle with the queue until after
510 * we release the spin lock.
512 * NOTES: The process queue is now a priority queue for locking.
515 ProcSleep(PROC_QUEUE *waitQueue,/* lock->waitProcs */
516 LOCKMETHODCTL *lockctl,
517 int token, /* lockmode */
521 SPINLOCK spinlock = lockctl->masterLock;
523 int myMask = (1 << token);
524 int waitMask = lock->waitMask;
525 int aheadHolders[MAX_LOCKMODES];
526 bool selfConflict = (lockctl->conflictTab[token] & myMask),
528 bool deadlock_checked = false;
529 struct itimerval timeval,
532 MyProc->token = token;
533 MyProc->waitLock = lock;
535 proc = (PROC *) MAKE_PTR(waitQueue->links.prev);
537 /* if we don't conflict with any waiter - be first in queue */
538 if (!(lockctl->conflictTab[token] & waitMask))
541 for (i = 1; i < MAX_LOCKMODES; i++)
542 aheadHolders[i] = lock->activeHolders[i];
543 (aheadHolders[token])++;
545 for (i = 0; i < waitQueue->size; i++)
547 /* am I waiting for him ? */
548 if (lockctl->conflictTab[token] & proc->holdLock)
550 /* is he waiting for me ? */
551 if (lockctl->conflictTab[proc->token] & MyProc->holdLock)
553 MyProc->errType = STATUS_ERROR;
554 elog(NOTICE, DeadLockMessage);
557 /* being waiting for him - go past */
559 /* if he waits for me */
560 else if (lockctl->conflictTab[proc->token] & MyProc->holdLock)
562 /* if conflicting locks requested */
563 else if (lockctl->conflictTab[proc->token] & myMask)
567 * If I request non self-conflicting lock and there are others
568 * requesting the same lock just before me - stay here.
570 if (!selfConflict && prevSame)
575 * Last attempt to don't move any more: if we don't conflict with
576 * rest waiters in queue.
578 else if (!(lockctl->conflictTab[token] & waitMask))
581 prevSame = (proc->token == token);
582 (aheadHolders[proc->token])++;
583 if (aheadHolders[proc->token] == lock->holders[proc->token])
584 waitMask &= ~(1 << proc->token);
585 proc = (PROC *) MAKE_PTR(proc->links.prev);
589 /* -------------------
590 * assume that these two operations are atomic (because
592 * -------------------
594 SHMQueueInsertTL(&(proc->links), &(MyProc->links));
597 lock->waitMask |= myMask;
598 SpinRelease(spinlock);
601 * We set this so we can wake up periodically and check for a deadlock.
602 * If a deadlock is detected, the handler releases the processes
603 * semaphore and aborts the current transaction.
605 * Need to zero out struct to set the interval and the micro seconds fields
609 MemSet(&timeval, 0, sizeof(struct itimerval));
610 timeval.it_value.tv_sec = \
611 (DeadlockCheckTimer ? DeadlockCheckTimer : DEADLOCK_CHECK_TIMER);
616 MyProc->errType = NO_ERROR; /* reset flag after deadlock check */
618 if (!deadlock_checked)
619 if (setitimer(ITIMER_REAL, &timeval, &dummy))
620 elog(FATAL, "ProcSleep: Unable to set timer for process wakeup");
621 deadlock_checked = true;
624 * if someone wakes us between SpinRelease and IpcSemaphoreLock,
625 * IpcSemaphoreLock will not block. The wakeup is "saved" by
626 * the semaphore implementation.
629 IpcSemaphoreLock(MyProc->sem.semId, MyProc->sem.semNum,
631 } while (MyProc->errType == STATUS_NOT_FOUND); /* sleep after deadlock
636 * We were awoken before a timeout - now disable the timer
639 timeval.it_value.tv_sec = 0;
640 if (setitimer(ITIMER_REAL, &timeval, &dummy))
641 elog(FATAL, "ProcSleep: Unable to diable timer for process wakeup");
644 * We were assumed to be in a critical section when we went
648 SpinAcquire(spinlock);
652 #ifdef LOCK_MGR_DEBUG
653 /* Just to get meaningful debug messages from DumpLocks() */
654 MyProc->waitLock = (LOCK *) NULL;
657 return MyProc->errType;
662 * ProcWakeup -- wake up a process by releasing its private semaphore.
664 * remove the process from the wait queue and set its links invalid.
665 * RETURN: the next process in the wait queue.
668 ProcWakeup(PROC *proc, int errType)
672 /* assume that spinlock has been acquired */
674 if (proc->links.prev == INVALID_OFFSET ||
675 proc->links.next == INVALID_OFFSET)
676 return (PROC *) NULL;
678 retProc = (PROC *) MAKE_PTR(proc->links.prev);
680 /* you have to update waitLock->waitProcs.size yourself */
681 SHMQueueDelete(&(proc->links));
682 SHMQueueElemInit(&(proc->links));
684 proc->errType = errType;
686 IpcSemaphoreUnlock(proc->sem.semId, proc->sem.semNum, IpcExclusiveLock);
692 * ProcLockWakeup -- routine for waking up processes when a lock is
696 ProcLockWakeup(PROC_QUEUE *queue, LOCKMETHOD lockmethod, LOCK *lock)
701 int last_locktype = 0;
702 int queue_size = queue->size;
704 Assert(queue->size >= 0);
707 return STATUS_NOT_FOUND;
709 proc = (PROC *) MAKE_PTR(queue->links.prev);
710 while ((queue_size--) && (proc))
714 * This proc will conflict as the previous one did, don't even
717 if (proc->token == last_locktype)
721 * Does this proc conflict with locks held by others ?
723 if (LockResolveConflicts(lockmethod,
727 (XIDLookupEnt *) NULL) != STATUS_OK)
731 last_locktype = proc->token;
736 * there was a waiting process, grant it the lock before waking it
737 * up. This will prevent another process from seizing the lock
738 * between the time we release the lock master (spinlock) and the
739 * time that the awoken process begins executing again.
741 GrantLock(lock, proc->token);
744 * ProcWakeup removes proc from the lock waiting process queue and
745 * returns the next proc in chain.
750 proc = ProcWakeup(proc, NO_ERROR);
753 Assert(queue->size >= 0);
759 /* Something is still blocking us. May have deadlocked. */
760 trace_flag = (lock->tag.lockmethod == USER_LOCKMETHOD) ? \
761 TRACE_USERLOCKS : TRACE_LOCKS;
763 "ProcLockWakeup: lock(%x) can't wake up any process",
765 #ifdef DEADLOCK_DEBUG
766 if (pg_options[trace_flag] >= 2)
769 return STATUS_NOT_FOUND;
774 ProcAddLock(SHM_QUEUE *elem)
776 SHMQueueInsertTL(&MyProc->lockQueue, elem);
779 /* --------------------
780 * We only get to this routine if we got SIGALRM after DEADLOCK_CHECK_TIMER
781 * while waiting for a lock to be released by some other process. If we have
782 * a real deadlock, we must also indicate that I'm no longer waiting
783 * on a lock so that other processes don't try to wake me up and screw
785 * --------------------
788 HandleDeadLock(SIGNAL_ARGS)
794 /* ---------------------
795 * Check to see if we've been awoken by anyone in the interim.
797 * If we have we can return and resume our transaction -- happy day.
798 * Before we are awoken the process releasing the lock grants it to
799 * us so we know that we don't have to wait anymore.
801 * Damn these names are LONG! -mer
802 * ---------------------
804 if (IpcSemaphoreGetCount(MyProc->sem.semId, MyProc->sem.semNum) ==
805 IpcSemaphoreDefaultStartValue)
812 * you would think this would be unnecessary, but...
814 * this also means we've been removed already. in some ports (e.g.,
815 * sparc and aix) the semop(2) implementation is such that we can
816 * actually end up in this handler after someone has removed us from
817 * the queue and bopped the semaphore *but the test above fails to
818 * detect the semaphore update* (presumably something weird having to
819 * do with the order in which the semaphore wakeup signal and SIGALRM
822 if (MyProc->links.prev == INVALID_OFFSET ||
823 MyProc->links.next == INVALID_OFFSET)
829 #ifdef DEADLOCK_DEBUG
833 MyProc->errType = STATUS_NOT_FOUND;
834 if (!DeadLockCheck(MyProc, MyProc->waitLock))
840 mywaitlock = MyProc->waitLock;
842 /* ------------------------
843 * Get this process off the lock's wait queue
844 * ------------------------
846 Assert(mywaitlock->waitProcs.size > 0);
848 --mywaitlock->waitProcs.size;
849 SHMQueueDelete(&(MyProc->links));
850 SHMQueueElemInit(&(MyProc->links));
852 /* ------------------
853 * Unlock my semaphore so that the count is right for next time.
854 * I was awoken by a signal, not by someone unlocking my semaphore.
857 IpcSemaphoreUnlock(MyProc->sem.semId, MyProc->sem.semNum,
861 * Set MyProc->errType to STATUS_ERROR so that we abort after
862 * returning from this handler.
865 MyProc->errType = STATUS_ERROR;
868 * if this doesn't follow the IpcSemaphoreUnlock then we get lock
869 * table corruption ("LockReplace: xid table corrupted") due to race
870 * conditions. i don't claim to understand this...
874 elog(NOTICE, DeadLockMessage);
879 ProcReleaseSpins(PROC *proc)
888 for (i = 0; i < (int) MAX_SPINS; i++)
892 Assert(proc->sLocks[i] == 1);
899 /*****************************************************************************
901 *****************************************************************************/
904 * ProcGetNewSemKeyAndNum -
905 * scan the free semaphore bitmap and allocate a single semaphore from
906 * a semaphore set. (If the semaphore set doesn't exist yet,
907 * IpcSemaphoreCreate will create it. Otherwise, we use the existing
911 ProcGetNewSemKeyAndNum(IPCKey *key, int *semNum)
914 int32 *freeSemMap = ProcGlobal->freeSemMap;
915 int32 fullmask = (1 << (PROC_NSEMS_PER_SET + 1)) - 1;
918 * we hold ProcStructLock when entering this routine. We scan through
919 * the bitmap to look for a free semaphore.
922 for (i = 0; i < MAX_PROC_SEMS / PROC_NSEMS_PER_SET; i++)
927 if (freeSemMap[i] == fullmask)
928 continue; /* this set is fully allocated */
930 for (j = 0; j < PROC_NSEMS_PER_SET; j++)
932 if ((freeSemMap[i] & mask) == 0)
936 * a free semaphore found. Mark it as allocated. Also set
937 * the bit indicating whole set is allocated.
939 freeSemMap[i] |= mask + (1 << PROC_NSEMS_PER_SET);
941 *key = ProcGlobal->currKey + i;
949 /* if we reach here, all the semaphores are in use. */
950 elog(ERROR, "InitProc: cannot allocate a free semaphore");
955 * free up our semaphore in the semaphore set.
958 ProcFreeSem(IpcSemaphoreKey semKey, int semNum)
962 int32 *freeSemMap = ProcGlobal->freeSemMap;
964 i = semKey - ProcGlobal->currKey;
965 mask = ~(1 << semNum);
966 freeSemMap[i] &= mask;
969 * Formerly we'd release a semaphore set if it was now completely
970 * unused, but now we keep the semaphores to ensure we won't run out
971 * when starting new backends --- cf. InitProcGlobal. Note that the
972 * PROC_NSEMS_PER_SET+1'st bit of the freeSemMap entry remains set to
973 * indicate it is still allocated; ProcFreeAllSemaphores() needs that.
978 * ProcFreeAllSemaphores -
979 * called at shmem_exit time, ie when exiting the postmaster or
980 * destroying shared state for a failed set of backends.
981 * Free up all the semaphores allocated to the lmgrs of the backends.
984 ProcFreeAllSemaphores()
987 int32 *freeSemMap = ProcGlobal->freeSemMap;
989 for (i = 0; i < MAX_PROC_SEMS / PROC_NSEMS_PER_SET; i++)
991 if (freeSemMap[i] != 0)
992 IpcSemaphoreKill(ProcGlobal->currKey + i);