linux-kernel - Re: [PATCH 5/5] cgroup: separate out cgroup_attach

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Message-ID: <20111220233502.GN10752@google.com>
Date:	Tue, 20 Dec 2011 15:35:02 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Mandeep Singh Baines <msb@...omium.org>
Cc:	Li Zefan <lizf@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <paul@...lmenage.org>
Subject: Re: [PATCH 5/5] cgroup: separate out cgroup_attach_proc error
 handling code

Hello,

On Tue, Dec 20, 2011 at 03:14:33PM -0800, Mandeep Singh Baines wrote:
> @@ -2067,9 +2067,10 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
>  	read_unlock(&tasklist_lock);
>  
>  	/* methods shouldn't be called if no task is actually migrating */
> -	retval = 0;
> -	if (!group_size)
> +	if (!group_size) {
> +		retval = 0;
>  		goto out_free_group_list;
> +	}

Eh... I don't think this is an improvement.  It's just different.

> @@ -2126,20 +2127,20 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
>  	 */
>  	synchronize_rcu();
>  	cgroup_wakeup_rmdir_waiter(cgrp);
> -	retval = 0;
> +	flex_array_free(group);
> +	return 0;

Hmm... maybe goto out_free_group_list?  Duplicating cleanup on success
and failure paths can lead future updaters forget one of them.  The
exit path in this function isn't pretty but I don't think the proposed
patch improves it either.

Thanks.

-- 
tejun
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