Subject: [merged] wait-fix-false-timeouts-when-using-wait_event_timeout.patch
removed from -mm tree
To:
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]
From: [email protected]
Date: Tue, 28 May 2013 12:36:39 -0700
The patch titled
Subject: wait: fix false timeouts when using wait_event_timeout()
has been removed from the -mm tree. Its filename was
wait-fix-false-timeouts-when-using-wait_event_timeout.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Imre Deak <[email protected]>
Subject: 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 <[email protected]>
Acked-by: Daniel Vetter <[email protected]>
Acked-by: David Howells <[email protected]>
Acked-by: Jens Axboe <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: Dave Jones <[email protected]>
Cc: Lukas Czerner <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
include/linux/wait.h | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff -puN
include/linux/wait.h~wait-fix-false-timeouts-when-using-wait_event_timeout
include/linux/wait.h
--- a/include/linux/wait.h~wait-fix-false-timeouts-when-using-wait_event_timeout
+++ a/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) \
({ \
_
Patches currently in -mm which might be from [email protected] are
origin.patch
linux-next.patch
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