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 <paul...@linux.vnet.ibm.com>
Cc: Tejun Heo <t...@kernel.org>
Cc: Christoph Lameter <c...@linux.com>
---
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 c13dceb87b60..1d0c18c59304 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -138,12 +138,12 @@ 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 fe03c6d52761..30e7dd88148b 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;
--
2.5.2
