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From: Bruce M Simpson <bms@FreeBSD.org>
Date: Thu, 12 Mar 2009 10:36:39 +0000 (UTC)
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Subject: svn commit: r189736 - head/sys/kern
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Author: bms
Date: Thu Mar 12 10:36:39 2009
New Revision: 189736
URL: http://svn.freebsd.org/changeset/base/189736

Log:
  Ensure that the semaphore value is re-checked after sem_lock
  is re-acquired, after the condition variable is signalled.
  
  PR:             http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/127545
  MFC after:      5 days
  Reviewed by:    attilio

Modified:
  head/sys/kern/uipc_sem.c

Modified: head/sys/kern/uipc_sem.c
==============================================================================
--- head/sys/kern/uipc_sem.c	Thu Mar 12 10:34:16 2009	(r189735)
+++ head/sys/kern/uipc_sem.c	Thu Mar 12 10:36:39 2009	(r189736)
@@ -727,7 +727,7 @@ kern_sem_wait(struct thread *td, semid_t
 #endif
 	DP(("kern_sem_wait value = %d, tryflag %d\n", ks->ks_value, tryflag));
 	vfs_timestamp(&ks->ks_atime);
-	if (ks->ks_value == 0) {
+	while (ks->ks_value == 0) {
 		ks->ks_waiters++;
 		if (tryflag != 0)
 			error = EAGAIN;