Author: davidxu
Date: Wed Aug 25 03:14:32 2010
New Revision: 211794
URL: http://svn.freebsd.org/changeset/base/211794
Log:
If a thread is removed from umtxq while sleeping, reset error code
to zero, this gives userland a better indication that a thread needn't
to be cancelled.
Modified:
head/sys/kern/kern_umtx.c
Modified: head/sys/kern/kern_umtx.c
==============================================================================
--- head/sys/kern/kern_umtx.c Wed Aug 25 02:09:07 2010 (r211793)
+++ head/sys/kern/kern_umtx.c Wed Aug 25 03:14:32 2010 (r211794)
@@ -1059,8 +1059,10 @@ do_wait(struct thread *td, void *addr, u
umtxq_lock(&uq->uq_key);
for (;;) {
error = umtxq_sleep(uq, "uwait", tvtohz(&tv));
- if (!(uq->uq_flags & UQF_UMTXQ))
+ if (!(uq->uq_flags & UQF_UMTXQ)) {
+ error = 0;
break;
+ }
if (error != ETIMEDOUT)
break;
umtxq_unlock(&uq->uq_key);
@@ -2404,25 +2406,14 @@ do_cv_wait(struct thread *td, struct uco
}
}
- if (error != 0) {
- if ((uq->uq_flags & UQF_UMTXQ) == 0) {
- /*
- * If we concurrently got do_cv_signal()d
- * and we got an error or UNIX signals or a timeout,
- * then, perform another umtxq_signal to avoid
- * consuming the wakeup. This may cause supurious
- * wakeup for another thread which was just queued,
- * but SUSV3 explicitly allows supurious wakeup to
- * occur, and indeed a kernel based implementation
- * can not avoid it.
- */
- if (!umtxq_signal(&uq->uq_key, 1))
- error = 0;
- }
+ if ((uq->uq_flags & UQF_UMTXQ) == 0)
+ error = 0;
+ else {
+ umtxq_remove(uq);
if (error == ERESTART)
error = EINTR;
}
- umtxq_remove(uq);
+
umtxq_unlock(&uq->uq_key);
umtx_key_release(&uq->uq_key);
return (error);
@@ -2891,15 +2882,13 @@ do_sem_wait(struct thread *td, struct _u
}
}
- if (error != 0) {
- if ((uq->uq_flags & UQF_UMTXQ) == 0) {
- if (!umtxq_signal(&uq->uq_key, 1))
- error = 0;
- }
+ if ((uq->uq_flags & UQF_UMTXQ) == 0)
+ error = 0;
+ else {
+ umtxq_remove(uq);
if (error == ERESTART)
error = EINTR;
}
- umtxq_remove(uq);
umtxq_unlock(&uq->uq_key);
umtx_key_release(&uq->uq_key);
return (error);
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