linux-kernel - [PATCH 1/3] cgroup - removing superfluous rcu_read_lock

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Message-Id: <1288638909-10541-2-git-send-email-jolsa@redhat.com>
Date:	Mon,  1 Nov 2010 20:15:07 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	dhowells@...hat.com, lizf@...fujitsu.com, paul.moore@...com,
	johannes@...solutions.net, dipankar@...ibm.com
Cc:	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, kvm@...r.kernel.org,
	Jiri Olsa <jolsa@...hat.com>
Subject: [PATCH 1/3] cgroup - removing superfluous rcu_read_lock_held check

hi,
the rcu_dereference_check is defined as

	#define rcu_dereference_check(p, c) \
	   __rcu_dereference_check((p), rcu_read_lock_held() || (c), __rcu)

so the caller does not need to specify rcu_read_lock_held() condition.

wbr,
jirka


Signed-off-by: Jiri Olsa <jolsa@...hat.com>
---
 include/linux/cgroup.h |    1 -
 kernel/cgroup.c        |    6 ++----
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index ed4ba11..caed568 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -536,7 +536,6 @@ static inline struct cgroup_subsys_state *cgroup_subsys_state(
  */
 #define task_subsys_state_check(task, subsys_id, __c)			\
 	rcu_dereference_check(task->cgroups->subsys[subsys_id],		\
-			      rcu_read_lock_held() ||			\
 			      lockdep_is_held(&task->alloc_lock) ||	\
 			      cgroup_lock_is_held() || (__c))
 
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 66a416b..1f329a2 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1687,7 +1687,6 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
 {
 	char *start;
 	struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
-						      rcu_read_lock_held() ||
 						      cgroup_lock_is_held());
 
 	if (!dentry || cgrp == dummytop) {
@@ -1713,7 +1712,6 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
 			break;
 
 		dentry = rcu_dereference_check(cgrp->dentry,
-					       rcu_read_lock_held() ||
 					       cgroup_lock_is_held());
 		if (!cgrp->parent)
 			continue;
@@ -4544,7 +4542,7 @@ unsigned short css_id(struct cgroup_subsys_state *css)
 	 * it's unchanged until freed.
 	 */
 	cssid = rcu_dereference_check(css->id,
-			rcu_read_lock_held() || atomic_read(&css->refcnt));
+			atomic_read(&css->refcnt));
 
 	if (cssid)
 		return cssid->id;
@@ -4557,7 +4555,7 @@ unsigned short css_depth(struct cgroup_subsys_state *css)
 	struct css_id *cssid;
 
 	cssid = rcu_dereference_check(css->id,
-			rcu_read_lock_held() || atomic_read(&css->refcnt));
+			atomic_read(&css->refcnt));
 
 	if (cssid)
 		return cssid->depth;
-- 
1.7.1

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