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| author |   Peter Zijlstra <peterz@infradead.org> | 2016-04-04 10:57:12 +0200 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2016-06-14 11:54:27 +0200 |
| commit | 1f03e8d2919270bd6ef64f39a45ce8df8a9f012a (patch) | |
| tree | 0cdd5de370212a021d0a1a3439bbc4b0a77fea8b /kernel/locking | |
| parent | Merge branch 'linus' into locking/core, to pick up fixes before merging new changes (diff) | |
| download | linux-dev-1f03e8d2919270bd6ef64f39a45ce8df8a9f012a.tar.xz linux-dev-1f03e8d2919270bd6ef64f39a45ce8df8a9f012a.zip | |
locking/barriers: Replace smp_cond_acquire() with smp_cond_load_acquire()
This new form allows using hardware assisted waiting.
Some hardware (ARM64 and x86) allow monitoring an address for changes,
so by providing a pointer we can use this to replace the cpu_relax()
with hardware optimized methods in the future.
Requested-by: Will Deacon <will.deacon@arm.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
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.c | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 2f9153b183c9..1b8dda90ebfa 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -475,7 +475,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) * sequentiality; this is because not all clear_pending_set_locked() * implementations imply full barriers. */ - smp_cond_acquire(!(atomic_read(&lock->val) & _Q_LOCKED_MASK)); + smp_cond_load_acquire(&lock->val.counter, !(VAL & _Q_LOCKED_MASK)); /* * take ownership and clear the pending bit. @@ -562,7 +562,7 @@ queue: * * The PV pv_wait_head_or_lock function, if active, will acquire * the lock and return a non-zero value. So we have to skip the - * smp_cond_acquire() call. As the next PV queue head hasn't been + * smp_cond_load_acquire() call. As the next PV queue head hasn't been * designated yet, there is no way for the locked value to become * _Q_SLOW_VAL. So both the set_locked() and the * atomic_cmpxchg_relaxed() calls will be safe. @@ -573,7 +573,7 @@ queue: if ((val = pv_wait_head_or_lock(lock, node))) goto locked; - smp_cond_acquire(!((val = atomic_read(&lock->val)) & _Q_LOCKED_PENDING_MASK)); + val = smp_cond_load_acquire(&lock->val.counter, !(VAL & _Q_LOCKED_PENDING_MASK)); locked: /* @@ -593,9 +593,9 @@ locked: break; } /* - * The smp_cond_acquire() call above has provided the necessary - * acquire semantics required for locking. At most two - * iterations of this loop may be ran. + * The smp_cond_load_acquire() call above has provided the + * necessary acquire semantics required for locking. At most + * two iterations of this loop may be ran. */ old = atomic_cmpxchg_relaxed(&lock->val, val, _Q_LOCKED_VAL); if (old == val) |