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Restructure backend SIGINT/SIGTERM handling so that 'die' interrupts

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are treated more like 'cancel' interrupts: the signal handler sets a
flag that is examined at well-defined spots, rather than trying to cope
with an interrupt that might happen anywhere.  See pghackers discussion
of 1/12/01.
This commit is contained in:
Tom Lane
2001-01-14 05:08:17 +00:00
parent 027f144e39
commit 36839c1927
24 changed files with 614 additions and 479 deletions
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35
src/backend/storage/lmgr/lock.c
View File

@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lock.c,v 1.76 2001/01/10 01:24:19 inoue Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lock.c,v 1.77 2001/01/14 05:08:15 tgl Exp $
*
* NOTES
* Outside modules can create a lock table and acquire/release
@@ -726,6 +726,12 @@ LockAcquire(LOCKMETHOD lockmethod, LOCKTAG *locktag,
*/
status = WaitOnLock(lockmethod, lockmode, lock, holder);
/*
* NOTE: do not do any material change of state between here and
* return. All required changes in locktable state must have been
* done when the lock was granted to us --- see notes in WaitOnLock.
*/
/*
* Check the holder entry status, in case something in the ipc
* communication doesn't work correctly.
@@ -921,6 +927,8 @@ GrantLock(LOCK *lock, HOLDER *holder, LOCKMODE lockmode)
lock->nActive++;
lock->activeHolders[lockmode]++;
lock->mask |= BITS_ON[lockmode];
if (lock->activeHolders[lockmode] == lock->holders[lockmode])
lock->waitMask &= BITS_OFF[lockmode];
LOCK_PRINT("GrantLock", lock, lockmode);
Assert((lock->nActive > 0) && (lock->activeHolders[lockmode] > 0));
Assert(lock->nActive <= lock->nHolding);
@@ -960,6 +968,17 @@ WaitOnLock(LOCKMETHOD lockmethod, LOCKMODE lockmode,
strcat(new_status, " waiting");
set_ps_display(new_status);
/*
* NOTE: Think not to put any lock state cleanup after the call to
* ProcSleep, in either the normal or failure path. The lock state
* must be fully set by the lock grantor, or by HandleDeadlock if we
* give up waiting for the lock. This is necessary because of the
* possibility that a cancel/die interrupt will interrupt ProcSleep
* after someone else grants us the lock, but before we've noticed it.
* Hence, after granting, the locktable state must fully reflect the
* fact that we own the lock; we can't do additional work on return.
*/
if (ProcSleep(lockMethodTable->ctl,
lockmode,
lock,
@@ -967,26 +986,16 @@ WaitOnLock(LOCKMETHOD lockmethod, LOCKMODE lockmode,
{
/* -------------------
* We failed as a result of a deadlock, see HandleDeadLock().
* Decrement the lock nHolding and holders fields as
* we are no longer waiting on this lock. Removal of the holder and
* lock objects, if no longer needed, will happen in xact cleanup.
* Quit now. Removal of the holder and lock objects, if no longer
* needed, will happen in xact cleanup (see above for motivation).
* -------------------
*/
lock->nHolding--;
lock->holders[lockmode]--;
LOCK_PRINT("WaitOnLock: aborting on lock", lock, lockmode);
Assert((lock->nHolding >= 0) && (lock->holders[lockmode] >= 0));
Assert(lock->nActive <= lock->nHolding);
if (lock->activeHolders[lockmode] == lock->holders[lockmode])
lock->waitMask &= BITS_OFF[lockmode];
SpinRelease(lockMethodTable->ctl->masterLock);
elog(ERROR, DeadLockMessage);
/* not reached */
}
if (lock->activeHolders[lockmode] == lock->holders[lockmode])
lock->waitMask &= BITS_OFF[lockmode];
set_ps_display(old_status);
pfree(old_status);
pfree(new_status);