mirror/postgresql
2
0
Fork 0
mirror of https://git.postgresql.org/git/postgresql.git synced 2025-01-12 18:34:36 +08:00
Code Issues Packages Projects Releases Wiki Activity

Whoops, I was a tad too enthusiastic about using shared lock mode for

Browse Source 
SInvalLock.  GetSnapshotData(true) has to use exclusive lock, since
it sets MyProc->xmin.
This commit is contained in:
Tom Lane 2001-09-29 15:29:48 +00:00
parent 6fdf7bed60
commit 2a314add00
1 changed files with 13 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
src/backend/storage/ipc/sinval.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.41 2001/09/29 04:02:24 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.42 2001/09/29 15:29:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -310,19 +310,24 @@ GetSnapshotData(bool serializable)
if (snapshot == NULL)
elog(ERROR, "Memory exhausted in GetSnapshotData");
snapshot->xmin = GetCurrentTransactionId();
LWLockAcquire(SInvalLock, LW_SHARED);
/*
* There can be no more than lastBackend active transactions, so this
* is enough space:
* Allocating space for MaxBackends xids is usually overkill;
* lastBackend would be sufficient. But it seems better to do the
* malloc while not holding the lock, so we can't look at lastBackend.
*/
snapshot->xip = (TransactionId *)
malloc(segP->lastBackend * sizeof(TransactionId));
malloc(MaxBackends * sizeof(TransactionId));
if (snapshot->xip == NULL)
elog(ERROR, "Memory exhausted in GetSnapshotData");
snapshot->xmin = GetCurrentTransactionId();
/*
* If we are going to set MyProc->xmin then we'd better get exclusive
* lock; if not, this is a read-only operation so it can be shared.
*/
LWLockAcquire(SInvalLock, serializable ? LW_EXCLUSIVE : LW_SHARED);
/*--------------------
* Unfortunately, we have to call ReadNewTransactionId() after acquiring
* SInvalLock above. It's not good because ReadNewTransactionId() does