Author: bms
Date: Sat Mar 14 01:12:35 2009
New Revision: 189781
URL: http://svn.freebsd.org/changeset/base/189781
Log:
MFC rev: 189736
Ensure that the semaphore value is re-checked after sem_lock
is re-acquired, after the condition variable is signalled.
Early MFC, as the test case in the PR is fairly complete and the
submitter also re-ran test case on -STABLE. It also bites Python
fairly hard, which will otherwise try to use POSIX sems for its
internal thread synchronization; this needs more in-depth testing.
PR: http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/127545
Reviewed by: attilio
Modified:
stable/7/sys/kern/uipc_sem.c
Modified: stable/7/sys/kern/uipc_sem.c
==============================================================================
--- stable/7/sys/kern/uipc_sem.c Sat Mar 14 00:33:08 2009
(r189780)
+++ stable/7/sys/kern/uipc_sem.c Sat Mar 14 01:12:35 2009
(r189781)
@@ -722,7 +722,7 @@ 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;
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