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Remove obsolete comments about sempahores from proc.c. 

Commit 6753333f switched from a semaphore-based wait to a latch-based
wait for ProcSleep()/ProcWakeup(), but left behind some stray references
to semaphores.

Back-patch to 9.5.

Reviewed-by: Daniel Gustafsson, Michael Paquier
Discussion: https://postgr.es/m/CA+hUKGLs5H6zhmgTijZ1OaJvC1sG0=AFXc1aHuce32tKiQrdEA@mail.gmail.com
This commit is contained in:
Thomas Munro 2019-06-21 10:57:07 +12:00
parent 20e1cc898d
commit 25b93a2967
1 changed files with 6 additions and 8 deletions
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14
src/backend/storage/lmgr/proc.c
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@ -1196,8 +1196,7 @@ ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
/*
* If we detected deadlock, give up without waiting. This must agree with
* CheckDeadLock's recovery code, except that we shouldn't release the
* semaphore since we haven't tried to lock it yet.
* CheckDeadLock's recovery code.
*/
if (early_deadlock)
{
@ -1233,9 +1232,9 @@ ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
/*
* Set timer so we can wake up after awhile and check for a deadlock. If a
* deadlock is detected, the handler releases the process's semaphore and
* sets MyProc->waitStatus = STATUS_ERROR, allowing us to know that we
* must report failure rather than success.
* deadlock is detected, the handler sets MyProc->waitStatus =
* STATUS_ERROR, allowing us to know that we must report failure rather
* than success.
*
* By delaying the check until we've waited for a bit, we can avoid
* running the rather expensive deadlock-check code in most cases.
@ -1578,7 +1577,7 @@ ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
/*
* ProcWakeup -- wake up a process by releasing its private semaphore.
* ProcWakeup -- wake up a process by setting its latch.
*
* Also remove the process from the wait queue and set its links invalid.
* RETURN: the next process in the wait queue.
@ -1713,8 +1712,7 @@ CheckDeadLock(void)
* we know that we don't have to wait anymore.
*
* We check by looking to see if we've been unlinked from the wait queue.
* This is quicker than checking our semaphore's state, since no kernel
* call is needed, and it is safe because we hold the lock partition lock.
* This is safe because we hold the lock partition lock.
*/
if (MyProc->links.prev == NULL ||
MyProc->links.next == NULL)