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| author | Peter Zijlstra <peterz@infradead.org> | 2015-10-16 14:39:38 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-12-04 10:33:41 +0100 |
| commit | b3e0b1b6d841a4b2f64fc09ea728913da8218424 (patch) | |
| tree | 93df412814210f3e4d36dae4e39487aec17a431e /kernel/locking/qspinlock.c | |
| parent | 829cf31751aa1c50b1527c1e0c821c99246b5639 (diff) | |
| download | linux-b3e0b1b6d841a4b2f64fc09ea728913da8218424.tar.gz linux-b3e0b1b6d841a4b2f64fc09ea728913da8218424.tar.bz2 linux-b3e0b1b6d841a4b2f64fc09ea728913da8218424.zip | |
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/qspinlock.c')
| -rw-r--r-- | kernel/locking/qspinlock.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 986207887def..ed9d96708f93 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: |