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Remove more obsolete comments about semaphores.

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Commit 6753333f stopped using semaphores as the sleep/wake mechanism for
heavyweight locks, but some obsolete references to that scheme remained
in comments.  As with similar commit 25b93a29, back-patch all the way.

Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Discussion: https://postgr.es/m/CA%2BhUKGLafjB1uzXcy%3D%3D2L3cy7rjHkqOVn7qRYGBjk%3D%3DtMJE7Yg%40mail.gmail.com
This commit is contained in:
Thomas Munro 2021-07-09 17:51:48 +12:00
parent 6de3a21bbc
commit 8d48a3436d
1 changed files with 9 additions and 18 deletions
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27
src/backend/storage/lmgr/lwlock.c
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@ -1302,14 +1302,10 @@ LWLockAcquire(LWLock *lock, LWLockMode mode)
/* /*
* Wait until awakened. * Wait until awakened.
* *
* Since we share the process wait semaphore with the regular lock * It is possible that we get awakened for a reason other than being
* manager and ProcWaitForSignal, and we may need to acquire an LWLock * signaled by LWLockRelease. If so, loop back and wait again. Once
* while one of those is pending, it is possible that we get awakened * we've gotten the LWLock, re-increment the sema by the number of
* for a reason other than being signaled by LWLockRelease. If so, * additional signals received.
* loop back and wait again. Once we've gotten the LWLock,
* re-increment the sema by the number of additional signals received,
* so that the lock manager or signal manager will see the received
* signal when it next waits.
*/ */
LOG_LWDEBUG("LWLockAcquire", lock, "waiting"); LOG_LWDEBUG("LWLockAcquire", lock, "waiting");
@ -1474,8 +1470,7 @@ LWLockAcquireOrWait(LWLock *lock, LWLockMode mode)
{ {
/* /*
* Wait until awakened. Like in LWLockAcquire, be prepared for * Wait until awakened. Like in LWLockAcquire, be prepared for
* bogus wakeups, because we share the semaphore with * bogus wakeups.
* ProcWaitForSignal.
*/ */
LOG_LWDEBUG("LWLockAcquireOrWait", lock, "waiting"); LOG_LWDEBUG("LWLockAcquireOrWait", lock, "waiting");
@ -1688,14 +1683,10 @@ LWLockWaitForVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval)
/* /*
* Wait until awakened. * Wait until awakened.
* *
* Since we share the process wait semaphore with the regular lock * It is possible that we get awakened for a reason other than being
* manager and ProcWaitForSignal, and we may need to acquire an LWLock * signaled by LWLockRelease. If so, loop back and wait again. Once
* while one of those is pending, it is possible that we get awakened * we've gotten the LWLock, re-increment the sema by the number of
* for a reason other than being signaled by LWLockRelease. If so, * additional signals received.
* loop back and wait again. Once we've gotten the LWLock,
* re-increment the sema by the number of additional signals received,
* so that the lock manager or signal manager will see the received
* signal when it next waits.
*/ */
LOG_LWDEBUG("LWLockWaitForVar", lock, "waiting"); LOG_LWDEBUG("LWLockWaitForVar", lock, "waiting");