Commit-ID: cb037fdad6772df2d49fe61c97d7c0d8265bc918 Gitweb: http://git.kernel.org/tip/cb037fdad6772df2d49fe61c97d7c0d8265bc918 Author: Waiman Long <[email protected]> AuthorDate: Thu, 10 Dec 2015 15:17:44 -0500 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 29 Feb 2016 10:02:42 +0100
locking/qspinlock: Use smp_cond_acquire() in pending code The newly introduced smp_cond_acquire() was used to replace the slowpath lock acquisition loop. Similarly, the new function can also be applied to the pending bit locking loop. This patch uses the new function in that loop. Signed-off-by: Waiman Long <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Douglas Hatch <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Scott J Norton <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- kernel/locking/qspinlock.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 393d187..ce2f75e 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -358,8 +358,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) * sequentiality; this is because not all clear_pending_set_locked() * implementations imply full barriers. */ - while ((val = smp_load_acquire(&lock->val.counter)) & _Q_LOCKED_MASK) - cpu_relax(); + smp_cond_acquire(!(atomic_read(&lock->val) & _Q_LOCKED_MASK)); /* * take ownership and clear the pending bit. @@ -435,7 +434,7 @@ 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_load_acquire() call. As the next PV queue head hasn't been + * smp_cond_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. @@ -466,7 +465,7 @@ locked: break; } /* - * The smp_load_acquire() call above has provided the necessary + * 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. */
