linux-kernel - Re: [PATCH for-3.4-fixes] cgroup: cgroup_attach

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Message-ID: <alpine.LNX.2.00.1203301037380.25526@pobox.suse.cz>
Date:	Fri, 30 Mar 2012 10:38:01 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Tejun Heo <tj@...nel.org>
Cc:	Mandeep Singh Baines <msb@...omium.org>, lizefan@...wei.com,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	Paul Menage <paul@...lmenage.org>,
	Kay Sievers <kay.sievers@...y.org>
Subject: Re: [PATCH for-3.4-fixes] cgroup: cgroup_attach_task() could return
 -errno after success

On Thu, 29 Mar 2012, Tejun Heo wrote:

> 61d1d219c4 "cgroup: remove extra calls to find_existing_css_set" made
> cgroup_task_migrate() return void.  An unfortunate side effect was
> that cgroup_attach_task() was depending on that function's return
> value to clear its @retval on the success path.  On cgroup mounts
> without any subsystem with ->can_attach() callback,
> cgroup_attach_task() ended up returning @retval without initializing
> it on success.
> 
> For some reason, gcc failed to warn about it and it didn't cause
> cgroup_attach_task() to return non-zero value in many cases, probably
> due to difference in register allocation.  When the problem
> materializes, systemd fails to populate /systemd cgroup mount and
> fails to boot.
> 
> Fix it by initializing @retval to zero on declaration.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Reported-by: Jiri Kosina <jkosina@...e.cz>
> LKML-Reference: <alpine.LNX.2.00.1203282354440.25526@...ox.suse.cz>
> ---
> Jiri, can you please confirm the fix?

Thanks Tejun, it works here.

Tested-by: Jiri Kosina <jkosina@...e.cz>

-- 
Jiri Kosina
SUSE Labs
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