The commit is pushed to "branch-rh7-3.10.0-229.7.2-ovz" and will appear at
https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-229.7.2.vz7.6.3
------>
commit 82f6802b3f09878172024c57ed12cf2da92cccd3
Author: Vladimir Davydov <vdavy...@parallels.com>
Date: Fri Aug 28 14:49:23 2015 +0400
ms/percpu-refcount: add __must_check to percpu_ref_init() and don't use
ACCESS_ONCE() in percpu_ref_kill_rcu()
Patchset description:
Pulling upstream patches converting css refcnt to percpu_ref.
https://jira.sw.ru/browse/PSBM-34174
Kent Overstreet (2):
percpu: implement generic percpu refcounting
percpu-refcount: Don't use silly cmpxchg()
Tejun Heo (9):
percpu-refcount: consistently use plain (non-sched) RCU
percpu-refcount: cosmetic updates
percpu-refcount: add __must_check to percpu_ref_init() and don't use
ACCESS_ONCE() in percpu_ref_kill_rcu()
percpu-refcount: implement percpu_ref_cancel_init()
percpu-refcount: implement percpu_tryget() along with
percpu_ref_kill_and_confirm()
percpu-refcount: use RCU-sched insted of normal RCU
cgroup: reorder the operations in cgroup_destroy_locked()
cgroup: split cgroup destruction into two steps
cgroup: use percpu refcnt for cgroup_subsys_states
===
This patch description:
From: Tejun Heo <t...@kernel.org>
Two small changes.
* Unlike most init functions, percpu_ref_init() allocates memory and
may fail. Let's mark it with __must_check in case the caller
forgets.
* percpu_ref_kill_rcu() is unnecessarily using ACCESS_ONCE() to
dereference @ref->pcpu_count, which can be misleading. The pointer
is guaranteed to be valid and visible and can't change underneath
the function. Drop ACCESS_ONCE().
Signed-off-by: Tejun Heo <t...@kernel.org>
(cherry picked from commit acac7883ee7bcc32476963bce7baf73d44574dd1)
Signed-off-by: Vladimir Davydov <vdavy...@parallels.com>
---
include/linux/percpu-refcount.h | 3 ++-
lib/percpu-refcount.c | 4 +---
2 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index b61bd6f..8146aa9 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -66,7 +66,8 @@ struct percpu_ref {
struct rcu_head rcu;
};
-int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release);
+int __must_check percpu_ref_init(struct percpu_ref *ref,
+ percpu_ref_func_t *release);
void percpu_ref_kill(struct percpu_ref *ref);
#define PCPU_STATUS_BITS 2
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index 9a78e55..b35eaac 100644
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -57,12 +57,10 @@ int percpu_ref_init(struct percpu_ref *ref,
percpu_ref_func_t *release)
static void percpu_ref_kill_rcu(struct rcu_head *rcu)
{
struct percpu_ref *ref = container_of(rcu, struct percpu_ref, rcu);
- unsigned __percpu *pcpu_count;
+ unsigned __percpu *pcpu_count = ref->pcpu_count;
unsigned count = 0;
int cpu;
- pcpu_count = ACCESS_ONCE(ref->pcpu_count);
-
/* Mask out PCPU_REF_DEAD */
pcpu_count = (unsigned __percpu *)
(((unsigned long) pcpu_count) & ~PCPU_STATUS_MASK);
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