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Allow an autovacuum worker to be interrupted automatically when it is found

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to be locking another process (except when it's working to prevent Xid
wraparound problems).
This commit is contained in:
Alvaro Herrera
2007-10-26 20:45:10 +00:00
parent ffda32e9fd
commit acac68b2bc
5 changed files with 114 additions and 7 deletions
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45
src/backend/storage/lmgr/deadlock.c
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@@ -12,7 +12,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/lmgr/deadlock.c,v 1.48 2007/06/19 20:13:21 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/lmgr/deadlock.c,v 1.49 2007/10/26 20:45:10 alvherre Exp $
*
* Interface:
*
@@ -109,6 +109,9 @@ static int maxPossibleConstraints;
static DEADLOCK_INFO *deadlockDetails;
static int nDeadlockDetails;
/* PGPROC pointer of any blocking autovacuum worker found */
static PGPROC *blocking_autovacuum_proc = NULL;
/*
* InitDeadLockChecking -- initialize deadlock checker during backend startup
@@ -206,6 +209,9 @@ DeadLockCheck(PGPROC *proc)
nPossibleConstraints = 0;
nWaitOrders = 0;
/* Initialize to not blocked by an autovacuum worker */
blocking_autovacuum_proc = NULL;
/* Search for deadlocks and possible fixes */
if (DeadLockCheckRecurse(proc))
{
@@ -255,10 +261,28 @@ DeadLockCheck(PGPROC *proc)
/* Return code tells caller if we had to escape a deadlock or not */
if (nWaitOrders > 0)
return DS_SOFT_DEADLOCK;
else if (blocking_autovacuum_proc != NULL)
return DS_BLOCKED_BY_AUTOVACUUM;
else
return DS_NO_DEADLOCK;
}
/*
* Return the PGPROC of the autovacuum that's blocking a process.
*
* We reset the saved pointer as soon as we pass it back.
*/
PGPROC *
GetBlockingAutoVacuumPgproc(void)
{
PGPROC *ptr;
ptr = blocking_autovacuum_proc;
blocking_autovacuum_proc = NULL;
return ptr;
}
/*
* DeadLockCheckRecurse -- recursively search for valid orderings
*
@@ -497,6 +521,25 @@ FindLockCycleRecurse(PGPROC *checkProc,
if ((proclock->holdMask & LOCKBIT_ON(lm)) &&
(conflictMask & LOCKBIT_ON(lm)))
{
/*
* Look for a blocking autovacuum. There can be more than
* one in the deadlock cycle, in which case we just pick a
* random one. We stash the autovacuum worker's PGPROC so
* that the caller can send a cancel signal to it, if
* appropriate.
*
* Note we read vacuumFlags without any locking. This is
* OK only for checking the PROC_IS_AUTOVACUUM flag,
* because that flag is set at process start and never
* reset; there is logic elsewhere to avoid cancelling an
* autovacuum that is working for preventing Xid wraparound
* problems (which needs to read a different vacuumFlag
* bit), but we don't do that here to avoid grabbing
* ProcArrayLock.
*/
if (proc->vacuumFlags & PROC_IS_AUTOVACUUM)
blocking_autovacuum_proc = proc;
/* This proc hard-blocks checkProc */
if (FindLockCycleRecurse(proc, depth + 1,
softEdges, nSoftEdges))