summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorImre Deak <imre.deak@intel.com>2013-05-24 15:55:09 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-05-24 16:22:50 -0700
commit4c663cfc523a88d97a8309b04a089c27dc57fd7e (patch)
treed3b9de53922dbc326017075bd5e1558b5f8c741d
parent7b92d03c3239f43e5b86c9cc9630f026d36ee995 (diff)
downloadlinux-3.10-4c663cfc523a88d97a8309b04a089c27dc57fd7e.tar.gz
linux-3.10-4c663cfc523a88d97a8309b04a089c27dc57fd7e.tar.bz2
linux-3.10-4c663cfc523a88d97a8309b04a089c27dc57fd7e.zip
wait: fix false timeouts when using wait_event_timeout()
Many callers of the wait_event_timeout() and wait_event_interruptible_timeout() expect that the return value will be positive if the specified condition becomes true before the timeout elapses. However, at the moment this isn't guaranteed. If the wake-up handler is delayed enough, the time remaining until timeout will be calculated as 0 - and passed back as a return value - even if the condition became true before the timeout has passed. Fix this by returning at least 1 if the condition becomes true. This semantic is in line with what wait_for_condition_timeout() does; see commit bb10ed09 ("sched: fix wait_for_completion_timeout() spurious failure under heavy load"). Daniel said "We have 3 instances of this bug in drm/i915. One case even where we switch between the interruptible and not interruptible wait_event_timeout variants, foolishly presuming they have the same semantics. I very much like this." One such bug is reported at https://bugs.freedesktop.org/show_bug.cgi?id=64133 Signed-off-by: Imre Deak <imre.deak@intel.com> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> Acked-by: David Howells <dhowells@redhat.com> Acked-by: Jens Axboe <axboe@kernel.dk> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Dave Jones <davej@redhat.com> Cc: Lukas Czerner <lczerner@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/wait.h16
1 files changed, 11 insertions, 5 deletions
diff --git a/include/linux/wait.h b/include/linux/wait.h
index ac38be2692d..1133695eb06 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -217,6 +217,8 @@ do { \
if (!ret) \
break; \
} \
+ if (!ret && (condition)) \
+ ret = 1; \
finish_wait(&wq, &__wait); \
} while (0)
@@ -233,8 +235,9 @@ do { \
* wake_up() has to be called after changing any variable that could
* change the result of the wait condition.
*
- * The function returns 0 if the @timeout elapsed, and the remaining
- * jiffies if the condition evaluated to true before the timeout elapsed.
+ * The function returns 0 if the @timeout elapsed, or the remaining
+ * jiffies (at least 1) if the @condition evaluated to %true before
+ * the @timeout elapsed.
*/
#define wait_event_timeout(wq, condition, timeout) \
({ \
@@ -302,6 +305,8 @@ do { \
ret = -ERESTARTSYS; \
break; \
} \
+ if (!ret && (condition)) \
+ ret = 1; \
finish_wait(&wq, &__wait); \
} while (0)
@@ -318,9 +323,10 @@ do { \
* wake_up() has to be called after changing any variable that could
* change the result of the wait condition.
*
- * The function returns 0 if the @timeout elapsed, -ERESTARTSYS if it
- * was interrupted by a signal, and the remaining jiffies otherwise
- * if the condition evaluated to true before the timeout elapsed.
+ * Returns:
+ * 0 if the @timeout elapsed, -%ERESTARTSYS if it was interrupted by
+ * a signal, or the remaining jiffies (at least 1) if the @condition
+ * evaluated to %true before the @timeout elapsed.
*/
#define wait_event_interruptible_timeout(wq, condition, timeout) \
({ \