Commit-ID: b393e8b33efd2ee08576ceddc10c2b4bfb3b5435 Gitweb: https://git.kernel.org/tip/b393e8b33efd2ee08576ceddc10c2b4bfb3b5435 Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> AuthorDate: Mon, 9 Oct 2017 10:20:44 -0700 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> CommitDate: Mon, 4 Dec 2017 10:52:53 -0800 percpu: READ_ONCE() now implies smp_read_barrier_depends() Because READ_ONCE() now implies smp_read_barrier_depends(), this commit removes the now-redundant smp_read_barrier_depends() following the READ_ONCE() in __ref_is_percpu(). Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Acked-by: Tejun Heo <tj@xxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> --- include/linux/percpu-refcount.h | 6 +++--- lib/percpu-refcount.c | 8 ++++---- 2 files changed, 7 insertions(+), 7 deletions(-) diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h index 6658d9e..864d167 100644 --- a/include/linux/percpu-refcount.h +++ b/include/linux/percpu-refcount.h @@ -139,12 +139,12 @@ static inline bool __ref_is_percpu(struct percpu_ref *ref, * when using it as a pointer, __PERCPU_REF_ATOMIC may be set in * between contaminating the pointer value, meaning that * READ_ONCE() is required when fetching it. + * + * The smp_read_barrier_depends() implied by READ_ONCE() pairs + * with smp_store_release() in __percpu_ref_switch_to_percpu(). */ percpu_ptr = READ_ONCE(ref->percpu_count_ptr); - /* paired with smp_store_release() in __percpu_ref_switch_to_percpu() */ - smp_read_barrier_depends(); - /* * Theoretically, the following could test just ATOMIC; however, * then we'd have to mask off DEAD separately as DEAD may be diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index fe03c6d..30e7dd8 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -197,10 +197,10 @@ static void __percpu_ref_switch_to_percpu(struct percpu_ref *ref) atomic_long_add(PERCPU_COUNT_BIAS, &ref->count); /* - * Restore per-cpu operation. smp_store_release() is paired with - * smp_read_barrier_depends() in __ref_is_percpu() and guarantees - * that the zeroing is visible to all percpu accesses which can see - * the following __PERCPU_REF_ATOMIC clearing. + * Restore per-cpu operation. smp_store_release() is paired + * with READ_ONCE() in __ref_is_percpu() and guarantees that the + * zeroing is visible to all percpu accesses which can see the + * following __PERCPU_REF_ATOMIC clearing. */ for_each_possible_cpu(cpu) *per_cpu_ptr(percpu_count, cpu) = 0; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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