linux-kernel - Re: [PATCH mmotm] cgroup: remove rcu_read_lock() from css_get

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Message-Id: <20090304132926.af5e47a0.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Wed, 4 Mar 2009 13:29:26 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	bharata@...ux.vnet.ibm.com
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	Paul Menage <menage@...gle.com>, Li Zefan <lizf@...fujitsu.com>
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 <bharata@...ux.vnet.ibm.com> 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 <bharata@...ux.vnet.ibm.com>

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

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>


> ---
>  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.
> 

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