From cb9242efe0abd8ed9129c16e91085a1675e72f30 Mon Sep 17 00:00:00 2001
From: Thomas Munro <tmunro@postgresql.org>
Date: Fri, 21 Jun 2019 10:57:07 +1200
Subject: [PATCH] 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
---
src/backend/storage/lmgr/proc.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index a82d473e202..f270db395a4 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -1040,8 +1040,7 @@ 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)
{
@@ -1077,9 +1076,9 @@ 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.
@@ -1404,7 +1403,7 @@ 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.
@@ -1539,8 +1538,7 @@ 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)
--
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