[PATCH 2/8] mutex: In mutex_can_spin_on_owner(), return false if task need_resched()

[Peter Zijlstra]

The mutex_can_spin_on_owner() function should also return false if the
task needs to be rescheduled to avoid entering the MCS queue when it
needs to reschedule.

Cc: chegu_vinod@xxxxxx
Cc: paulmck@xxxxxxxxxxxxxxxxxx
Cc: Waiman.Long@xxxxxx
Cc: torvalds@xxxxxxxxxxxxxxxxxxxx
Cc: tglx@xxxxxxxxxxxxx
Cc: riel@xxxxxxxxxx
Cc: akpm@xxxxxxxxxxxxxxxxxxxx
Cc: davidlohr@xxxxxx
Cc: hpa@xxxxxxxxx
Cc: andi@xxxxxxxxxxxxxx
Cc: aswin@xxxxxx
Cc: mingo@xxxxxxxxxx
Cc: scott.norton@xxxxxx
Signed-off-by: Jason Low <jason.low2@xxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1390936396-3962-2-git-send-email-jason.low2@xxxxxx
---
 kernel/locking/mutex.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -166,6 +166,9 @@ static inline int mutex_can_spin_on_owne
 	struct task_struct *owner;
 	int retval = 1;
 
+	if (need_resched())
+		return 0;
+
 	rcu_read_lock();
 	owner = ACCESS_ONCE(lock->owner);
 	if (owner)


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