From: Li Zefan <lizf@cn.fujitsu.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Paul Menage" <menage@google.com>,
"David Rientjes" <rientjes@google.com>,
"缪 勰" <miaox@cn.fujitsu.com>, LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org
Subject: Re: [PATCH] cpuset: Add a missing unlock in cpuset_write_resmask()
Date: Tue, 01 Mar 2011 09:05:22 +0800 [thread overview]
Message-ID: <4D6C4652.6030804@cn.fujitsu.com> (raw)
In-Reply-To: <20110228155524.6d7563e0.akpm@linux-foundation.org>
>> @@ -1561,8 +1561,10 @@ static int cpuset_write_resmask(struct cgroup *cgrp, struct cftype *cft,
>> return -ENODEV;
>>
>> trialcs = alloc_trial_cpuset(cs);
>> - if (!trialcs)
>> + if (!trialcs) {
>> + cgroup_unlock();
>> return -ENOMEM;
>> + }
>>
>> switch (cft->private) {
>> case FILE_CPULIST:
>
> It would be better to avoid multiple returns - it leads to more
> maintainable code and often shorter code:
>
I have no strong opinion on this.
> --- a/kernel/cpuset.c~cpuset-add-a-missing-unlock-in-cpuset_write_resmask-fix
> +++ a/kernel/cpuset.c
> @@ -1562,8 +1562,8 @@ static int cpuset_write_resmask(struct c
>
> trialcs = alloc_trial_cpuset(cs);
> if (!trialcs) {
> - cgroup_unlock();
> - return -ENOMEM;
> + retval = -ENOMEM;
> + goto out;
> }
>
> switch (cft->private) {
> @@ -1579,6 +1579,7 @@ static int cpuset_write_resmask(struct c
> }
>
> free_trial_cpuset(trialcs);
> +out:
> cgroup_unlock();
> return retval;
> }
> _
>
> also, alloc_trial_cpuset() is a fairly slow-looking function.
> cpuset_write_resmask() could run alloc_trial_cpuset() before running
> cgroup_lock_live_group(), thereby reducing lock hold times.
>
Nope. alloc_trial_cpuset() will read 'cs', so it must be protected by
the lock.
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prev parent reply other threads:[~2011-03-01 1:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-24 6:58 Li Zefan
2011-02-24 7:05 ` David Rientjes
2011-02-28 23:55 ` Andrew Morton
2011-03-01 1:05 ` Li Zefan [this message]
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