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authorPeter Zijlstra <peterz@infradead.org>2015-10-16 14:39:38 +0200
committerIngo Molnar <mingo@kernel.org>2015-12-04 10:33:41 +0100
commitb3e0b1b6d841a4b2f64fc09ea728913da8218424 (patch)
tree93df412814210f3e4d36dae4e39487aec17a431e /kernel/locking
parent829cf31751aa1c50b1527c1e0c821c99246b5639 (diff)
downloadop-kernel-dev-b3e0b1b6d841a4b2f64fc09ea728913da8218424.zip
op-kernel-dev-b3e0b1b6d841a4b2f64fc09ea728913da8218424.tar.gz
locking, sched: Introduce smp_cond_acquire() and use it
Introduce smp_cond_acquire() which combines a control dependency and a read barrier to form acquire semantics. This primitive has two benefits: - it documents control dependencies, - its typically cheaper than using smp_load_acquire() in a loop. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/locking')
-rw-r--r--kernel/locking/qspinlock.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 9862078..ed9d967 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -433,8 +433,7 @@ queue:
*
*/
pv_wait_head(lock, node);
- while ((val = smp_load_acquire(&lock->val.counter)) & _Q_LOCKED_PENDING_MASK)
- cpu_relax();
+ smp_cond_acquire(!((val = atomic_read(&lock->val)) & _Q_LOCKED_PENDING_MASK));
/*
* claim the lock:
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