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Commitc85c941

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Detect early deadlock in Hot Standby when Startup is already waiting. First
stage of required deadlock detection to allow re-enabling max_standby_delaysetting of -1, which is now essential in the absence of improved relation-specific conflict resoluton. Requested by Greg Stark et al.
1 parent034fffb commitc85c941

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3 files changed

+46
-4
lines changed

3 files changed

+46
-4
lines changed

‎src/backend/storage/ipc/standby.c‎

Lines changed: 36 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@
1111
* Portions Copyright (c) 1994, Regents of the University of California
1212
*
1313
* IDENTIFICATION
14-
* $PostgreSQL: pgsql/src/backend/storage/ipc/standby.c,v 1.8 2010/01/29 17:10:05 sriggs Exp $
14+
* $PostgreSQL: pgsql/src/backend/storage/ipc/standby.c,v 1.9 2010/01/31 19:01:11 sriggs Exp $
1515
*
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*-------------------------------------------------------------------------
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*/
@@ -22,6 +22,7 @@
2222
#include"access/xlog.h"
2323
#include"miscadmin.h"
2424
#include"pgstat.h"
25+
#include"storage/bufmgr.h"
2526
#include"storage/lmgr.h"
2627
#include"storage/proc.h"
2728
#include"storage/procarray.h"
@@ -384,7 +385,7 @@ ResolveRecoveryConflictWithBufferPin(void)
384385
TimestampDifference(GetLatestXLogTime(),now,
385386
&standby_delay_secs,&standby_delay_usecs);
386387

387-
if (standby_delay_secs >=(long)MaxStandbyDelay)
388+
if (standby_delay_secs >=MaxStandbyDelay)
388389
SendRecoveryConflictWithBufferPin();
389390
else
390391
{
@@ -445,6 +446,39 @@ SendRecoveryConflictWithBufferPin(void)
445446
CancelDBBackends(InvalidOid,PROCSIG_RECOVERY_CONFLICT_BUFFERPIN, false);
446447
}
447448

449+
/*
450+
* In Hot Standby perform early deadlock detection. We abort the lock
451+
* wait if are about to sleep while holding the buffer pin that Startup
452+
* process is waiting for. The deadlock occurs because we can only be
453+
* waiting behind an AccessExclusiveLock, which can only clear when a
454+
* transaction completion record is replayed, which can only occur when
455+
* Startup process is not waiting. So if Startup process is waiting we
456+
* never will clear that lock, so if we wait we cause deadlock. If we
457+
* are the Startup process then no need to check for deadlocks.
458+
*/
459+
void
460+
CheckRecoveryConflictDeadlock(LWLockIdpartitionLock)
461+
{
462+
Assert(!InRecovery);
463+
464+
if (!HoldingBufferPinThatDelaysRecovery())
465+
return;
466+
467+
LWLockRelease(partitionLock);
468+
469+
/*
470+
* Error message should match ProcessInterrupts() but we avoid calling
471+
* that because we aren't handling an interrupt at this point. Note
472+
* that we only cancel the current transaction here, so if we are in a
473+
* subtransaction and the pin is held by a parent, then the Startup
474+
* process will continue to wait even though we have avoided deadlock.
475+
*/
476+
ereport(ERROR,
477+
(errcode(ERRCODE_QUERY_CANCELED),
478+
errmsg("canceling statement due to conflict with recovery"),
479+
errdetail("User transaction caused buffer deadlock with recovery.")));
480+
}
481+
448482
/*
449483
* -----------------------------------------------------
450484
* Locking in Recovery Mode

‎src/backend/storage/lmgr/lock.c‎

Lines changed: 8 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.193 2010/01/29 19:45:12 sriggs Exp $
11+
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.194 2010/01/31 19:01:11 sriggs Exp $
1212
*
1313
* NOTES
1414
* A lock table is a shared memory hash table. When
@@ -814,6 +814,13 @@ LockAcquireExtended(const LOCKTAG *locktag,
814814
returnLOCKACQUIRE_NOT_AVAIL;
815815
}
816816

817+
/*
818+
* In Hot Standby perform early deadlock detection in normal backends.
819+
* If deadlock found we release partition lock but do not return.
820+
*/
821+
if (RecoveryInProgress()&& !InRecovery)
822+
CheckRecoveryConflictDeadlock(partitionLock);
823+
817824
/*
818825
* Set bitmask of locks this process already holds on this object.
819826
*/

‎src/include/storage/standby.h‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/storage/standby.h,v 1.6 2010/01/29 17:10:05 sriggs Exp $
10+
* $PostgreSQL: pgsql/src/include/storage/standby.h,v 1.7 2010/01/31 19:01:11 sriggs Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -31,6 +31,7 @@ extern void ResolveRecoveryConflictWithDatabase(Oid dbid);
3131

3232
externvoidResolveRecoveryConflictWithBufferPin(void);
3333
externvoidSendRecoveryConflictWithBufferPin(void);
34+
externvoidCheckRecoveryConflictDeadlock(LWLockIdpartitionLock);
3435

3536
/*
3637
* Standby Rmgr (RM_STANDBY_ID)

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