[src/trunk]: src/lib/libpthread pthread_rwlock_timedrdlock() and pthread_rwlo...

[nathanw <nathanw%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/583b9b6f82cd
branches:  trunk
changeset: 572607:583b9b6f82cd
user:      nathanw <nathanw%NetBSD.org@localhost>
date:      Sun Jan 09 01:57:38 2005 +0000

description:
pthread_rwlock_timedrdlock() and pthread_rwlock_timedwrlock():
After exiting the try-again loop, make one more test of the lock
conditions, in case it was released while a signal handler kept the
thread busy past the alarm expiration.

diffstat:

 lib/libpthread/pthread_rwlock.c |  16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

diffs (46 lines):

diff -r 9019149bba94 -r 583b9b6f82cd lib/libpthread/pthread_rwlock.c
--- a/lib/libpthread/pthread_rwlock.c   Sun Jan 09 01:47:20 2005 +0000
+++ b/lib/libpthread/pthread_rwlock.c   Sun Jan 09 01:57:38 2005 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pthread_rwlock.c,v 1.10 2005/01/09 01:47:20 nathanw Exp $ */
+/*     $NetBSD: pthread_rwlock.c,v 1.11 2005/01/09 01:57:38 nathanw Exp $ */
 
 /*-
  * Copyright (c) 2002 The NetBSD Foundation, Inc.
@@ -37,7 +37,7 @@
  */
 
 #include <sys/cdefs.h>
-__RCSID("$NetBSD: pthread_rwlock.c,v 1.10 2005/01/09 01:47:20 nathanw Exp $");
+__RCSID("$NetBSD: pthread_rwlock.c,v 1.11 2005/01/09 01:57:38 nathanw Exp $");
 
 #include <errno.h>
 
@@ -296,8 +296,14 @@
                pthread_spinlock(self, &rwlock->ptr_interlock);
        }
 
-       if (retval == 0)
+       /* One last chance to get the lock, in case it was released between
+          the alarm firing and when this thread got rescheduled, or in case
+          a signal handler kept it busy */
+       if ((rwlock->ptr_writer == NULL) &&
+           (PTQ_EMPTY(&rwlock->ptr_wblocked))) {
                rwlock->ptr_nreaders++;
+               retval = 0;
+       }
        pthread_spinunlock(self, &rwlock->ptr_interlock);
 
        return retval;
@@ -359,8 +365,10 @@
                pthread_spinlock(self, &rwlock->ptr_interlock);
        }
 
-       if (retval == 0)
+       if ((rwlock->ptr_nreaders == 0) && (rwlock->ptr_writer == NULL)) {
                rwlock->ptr_writer = self;
+               retval = 0;
+       }
        pthread_spinunlock(self, &rwlock->ptr_interlock);
 
        return retval;