[v2] futex: lower the lock contention on the HB lock during wake up
diff mbox

Message ID alpine.DEB.2.11.1506192053280.4107@nanos
State New
Headers show

Commit Message

Thomas Gleixner June 19, 2015, 6:54 p.m. UTC
On Fri, 19 Jun 2015, Kevin Hilman wrote:
> On Wed, Jun 17, 2015 at 1:33 AM, Sebastian Andrzej Siewior
> A handful of boot test failures on ARM/OMAP were found by kernelci.org
> in next-20150619[1] and were bisected down to this patch, which hit
> next-20150619 in the form of commit 881bd58d6e9e (futex: Lower the
> lock contention on the HB lock during wake up).  I confirmed that
> reverting that patch on top of next-20150619 gets things booting again
> for the affected platforms.
> 
> I haven't debugged this any further, but full boot logs are available
> for the boot failures[2][3] and the linux-omap list and maintainer are
> Cc'd here to help investigate further if needed.

Found it. Dunno, how I missed that one. Fix below.

Thanks,

	tglx
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Comments

Kevin Hilman June 19, 2015, 7:32 p.m. UTC | #1
Thomas Gleixner <tglx@linutronix.de> writes:

> On Fri, 19 Jun 2015, Kevin Hilman wrote:
>> On Wed, Jun 17, 2015 at 1:33 AM, Sebastian Andrzej Siewior
>> A handful of boot test failures on ARM/OMAP were found by kernelci.org
>> in next-20150619[1] and were bisected down to this patch, which hit
>> next-20150619 in the form of commit 881bd58d6e9e (futex: Lower the
>> lock contention on the HB lock during wake up).  I confirmed that
>> reverting that patch on top of next-20150619 gets things booting again
>> for the affected platforms.
>> 
>> I haven't debugged this any further, but full boot logs are available
>> for the boot failures[2][3] and the linux-omap list and maintainer are
>> Cc'd here to help investigate further if needed.
>
> Found it. Dunno, how I missed that one. Fix below.
>

Yup, that fix on top of next-20150619 gets the two OMAP platforms
booting again.

Tested-by: Kevin Hilman <khilman@linaro.org>

Kevin
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Patch
diff mbox

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 10dbeb6fe96f..5674b073473c 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1365,9 +1365,14 @@  rt_mutex_fastunlock(struct rt_mutex *lock,
 	if (likely(rt_mutex_cmpxchg(lock, current, NULL))) {
 		rt_mutex_deadlock_account_unlock(current);
 
-	} else if (slowfn(lock, &wake_q)) {
+	} else {
+		bool deboost = slowfn(lock, &wake_q);
+
+		wake_up_q(&wake_q);
+
 		/* Undo pi boosting if necessary: */
-		rt_mutex_adjust_prio(current);
+		if (deboost)
+			rt_mutex_adjust_prio(current);
 	}
 }