@@ -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) \
({ \
This is a note to let you know that I have just added a patch titled wait: fix false timeouts when using wait_event_timeout() to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue This patch is scheduled to be released in version 3.8.13.2. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.8.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From a870c27bde09d40caf2890b9aa5cc508c7a3d0ad Mon Sep 17 00:00:00 2001 From: Imre Deak <imre.deak@intel.com> Date: Fri, 24 May 2013 15:55:09 -0700 Subject: wait: fix false timeouts when using wait_event_timeout() commit 4c663cfc523a88d97a8309b04a089c27dc57fd7e upstream. 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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- include/linux/wait.h | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) -- 1.8.1.2