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Split the shared-memory array of PGPROC pointers out of the sinval

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communication structure, and make it its own module with its own lock.
This should reduce contention at least a little, and it definitely makes
the code seem cleaner.  Per my recent proposal.
This commit is contained in:
Tom Lane
2005-05-19 21:35:48 +00:00
parent 6910032a56
commit ee3b71f6bc
30 changed files with 923 additions and 860 deletions
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28
src/backend/access/transam/xact.c
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@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.200 2005/04/28 21:47:10 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.201 2005/05/19 21:35:45 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -34,7 +34,7 @@
#include "miscadmin.h"
#include "storage/fd.h"
#include "storage/proc.h"
#include "storage/sinval.h"
#include "storage/procarray.h"
#include "storage/smgr.h"
#include "utils/flatfiles.h"
#include "utils/guc.h"
@ -1503,16 +1503,18 @@ CommitTransaction(void)
* this must be done _before_ releasing locks we hold and _after_
* RecordTransactionCommit.
*
* LWLockAcquire(SInvalLock) is required: UPDATE with xid 0 is blocked by
* xid 1' UPDATE, xid 1 is doing commit while xid 2 gets snapshot - if
* xid 2' GetSnapshotData sees xid 1 as running then it must see xid 0
* as running as well or it will see two tuple versions - one deleted
* by xid 1 and one inserted by xid 0. See notes in GetSnapshotData.
* LWLockAcquire(ProcArrayLock) is required; consider this example:
* UPDATE with xid 0 is blocked by xid 1's UPDATE.
* xid 1 is doing commit while xid 2 gets snapshot.
* If xid 2's GetSnapshotData sees xid 1 as running then it must see
* xid 0 as running as well, or it will be able to see two tuple versions
* - one deleted by xid 1 and one inserted by xid 0. See notes in
* GetSnapshotData.
*/
if (MyProc != NULL)
{
/* Lock SInvalLock because that's what GetSnapshotData uses. */
LWLockAcquire(SInvalLock, LW_EXCLUSIVE);
/* Lock ProcArrayLock because that's what GetSnapshotData uses. */
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
MyProc->xid = InvalidTransactionId;
MyProc->xmin = InvalidTransactionId;
@ -1520,7 +1522,7 @@ CommitTransaction(void)
MyProc->subxids.nxids = 0;
MyProc->subxids.overflowed = false;
LWLockRelease(SInvalLock);
LWLockRelease(ProcArrayLock);
}
/*
@ -1688,8 +1690,8 @@ AbortTransaction(void)
*/
if (MyProc != NULL)
{
/* Lock SInvalLock because that's what GetSnapshotData uses. */
LWLockAcquire(SInvalLock, LW_EXCLUSIVE);
/* Lock ProcArrayLock because that's what GetSnapshotData uses. */
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
MyProc->xid = InvalidTransactionId;
MyProc->xmin = InvalidTransactionId;
@ -1697,7 +1699,7 @@ AbortTransaction(void)
MyProc->subxids.nxids = 0;
MyProc->subxids.overflowed = false;
LWLockRelease(SInvalLock);
LWLockRelease(ProcArrayLock);
}
/*