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authorPeter Zijlstra <peterz@infradead.org>2015-09-04 17:25:23 +0200
committerIngo Molnar <mingo@kernel.org>2015-09-11 07:49:42 +0200
commit43b3f02899f74ae9914a39547cc5492156f0027a (patch)
tree0db5018c95f8d243b974f42abda1c0c618abeee5 /kernel/locking/qspinlock.c
parentedcd591c77a48da753456f92daf8bb50fe9bac93 (diff)
downloadlwn-43b3f02899f74ae9914a39547cc5492156f0027a.tar.gz
lwn-43b3f02899f74ae9914a39547cc5492156f0027a.zip
locking/qspinlock/x86: Fix performance regression under unaccelerated VMs
Dave ran into horrible performance on a VM without PARAVIRT_SPINLOCKS set and Linus noted that the test-and-set implementation was retarded. One should spin on the variable with a load, not a RMW. While there, remove 'queued' from the name, as the lock isn't queued at all, but a simple test-and-set. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Reported-by: Dave Chinner <david@fromorbit.com> Tested-by: Dave Chinner <david@fromorbit.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Waiman Long <Waiman.Long@hp.com> Cc: stable@vger.kernel.org # v4.2+ Link: http://lkml.kernel.org/r/20150904152523.GR18673@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/locking/qspinlock.c')
-rw-r--r--kernel/locking/qspinlock.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 337c8818541d..87e9ce6a63c5 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -289,7 +289,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
if (pv_enabled())
goto queue;
- if (virt_queued_spin_lock(lock))
+ if (virt_spin_lock(lock))
return;
/*