The patch titled
rt-mutex: fix stale return value
has been added to the -mm tree. Its filename is
rt-mutex-fix-stale-return-value.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: rt-mutex: fix stale return value
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Alexey Kuznetsov found some problems in the pi-futex code.
The major problem is a stale return value in rt_mutex_slowlock():
When the pi chain walk returns -EDEADLK, but the waiter was woken up during
the phases where the locks were dropped, the rtmutex could be acquired, but
due to the stale return value -EDEADLK returned to the caller.
Reset the return value in the retry path.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Alexey Kuznetsov <kuznet@xxxxxxxxxxxxx>
Cc: Ulrich Drepper <drepper@xxxxxxxxxx>
Cc: Eric Dumazet <dada1@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/rtmutex.c | 11 +++++++++--
1 files changed, 9 insertions(+), 2 deletions(-)
diff -puN kernel/rtmutex.c~rt-mutex-fix-stale-return-value kernel/rtmutex.c
--- a/kernel/rtmutex.c~rt-mutex-fix-stale-return-value
+++ a/kernel/rtmutex.c
@@ -636,9 +636,16 @@ rt_mutex_slowlock(struct rt_mutex *lock,
* all over without going into schedule to try
* to get the lock now:
*/
- if (unlikely(!waiter.task))
+ if (unlikely(!waiter.task)) {
+ /*
+ * Reset the return value. We might
+ * have returned with -EDEADLK and the
+ * owner released the lock while we
+ * were walking the pi chain.
+ */
+ ret = 0;
continue;
-
+ }
if (unlikely(ret))
break;
}
_
Patches currently in -mm which might be from tglx@xxxxxxxxxxxxx are
rt-mutex-fix-stale-return-value.patch
rt-mutex-fix-chain-walk-early-wakeup-bug.patch
pi-futex-fix-exit-races-and-locking-problems.patch
git-acpi-add-exports.patch
git-arm.patch
s390-spinlock-initializer-cleanup.patch
i386-hpet-check-if-the-counter-works.patch
remove-clockevents_releaserequest_device.patch
add-a-flag-to-indicate-deferrable-timers-in-proc-timer_stats.patch
lguest-the-host-code-use-hrtimers.patch
futex-tidy-up-the-code.patch
-
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