2009-03-04 04:29:10

by Bharata B Rao

Subject: [PATCH mmotm] cgroup: remove rcu_read_lock() from css_get_next()

cgroup: remove rcu_read_lock() from css_get_next()

Callers of css_get_next() are already calling css_get_next()
under rcu_read_lock() and hence there there is no need for
css_get_next() to re-acquire rcu_read_lock(). As per the
comments in css_get_next(), let the callers accquire the
rcu_read_lock().

Signed-off-by: Bharata B Rao <[email protected]>
---
kernel/cgroup.c | 3 ---
1 file changed, 3 deletions(-)

--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3553,7 +3553,6 @@ css_get_next(struct cgroup_subsys *ss, i
return NULL;

BUG_ON(!ss->use_id);
- rcu_read_lock();
/* fill start point for scan */
tmpid = id;
while (1) {
@@ -3577,8 +3576,6 @@ css_get_next(struct cgroup_subsys *ss, i
/* continue to scan from next id */
tmpid = tmpid + 1;
}
-
- rcu_read_unlock();
return ret;
}

Regards,
Bharata.

2009-03-04 04:31:00

by Kamezawa Hiroyuki

Subject: Re: [PATCH mmotm] cgroup: remove rcu_read_lock() from css_get_next()

On Wed, 4 Mar 2009 09:59:20 +0530
Bharata B Rao <[email protected]> wrote:

> cgroup: remove rcu_read_lock() from css_get_next()
>
> Callers of css_get_next() are already calling css_get_next()
> under rcu_read_lock() and hence there there is no need for
> css_get_next() to re-acquire rcu_read_lock(). As per the
> comments in css_get_next(), let the callers accquire the
> rcu_read_lock().
>
> Signed-off-by: Bharata B Rao <[email protected]>

Yes, thank you for pointing out. This should be done by caller.

Acked-by: KAMEZAWA Hiroyuki <[email protected]>


> ---
> kernel/cgroup.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -3553,7 +3553,6 @@ css_get_next(struct cgroup_subsys *ss, i
> return NULL;
>
> BUG_ON(!ss->use_id);
> - rcu_read_lock();
> /* fill start point for scan */
> tmpid = id;
> while (1) {
> @@ -3577,8 +3576,6 @@ css_get_next(struct cgroup_subsys *ss, i
> /* continue to scan from next id */
> tmpid = tmpid + 1;
> }
> -
> - rcu_read_unlock();
> return ret;
> }
>
> Regards,
> Bharata.
>