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".
Signed-off-by: Imre Deak <imre.d...@intel.com>
---
include/linux/wait.h | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/include/linux/wait.h b/include/linux/wait.h
index 7cb64d4..5336842 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) \
({ \
--
1.7.10.4
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
