From: Lai Jiangshan <laijs@cn.fujitsu.com>
To: Paul Menage <menage@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Containers <containers@lists.linux-foundation.org>
Subject: Re: [PATCH] cpuset: rcu_read_lock() to protect task_cs() even we don't dereference to task_cs()'s return value
Date: Sat, 22 Nov 2008 11:01:01 +0800 [thread overview]
Message-ID: <492775ED.1040803@cn.fujitsu.com> (raw)
In-Reply-To: <6599ad830811211107n141e6cb5n2abf14e59110d764@mail.gmail.com>
Paul Menage wrote:
> On Fri, Nov 21, 2008 at 11:05 AM, Paul Menage <menage@google.com> wrote:
>> Wouldn't this be fixed by your patch that adds an rcu_read_lock() to
>> task_subsys_state() ?
>>
>
> Sorry, your other patch actually adds the rcu_read_lock() to
> task_cgroup(). But adding an rcu_read_lock() to task_subsys_state()
> would also help here.
Adding an rcu_read_lock() to task_subsys_state() also help here.
But task_subsys_state() is used in fast path.
If we add an implicit rcu_read_lock() in task_subsys_state(),
we still need rcu_read_lock()/task_lock() for using it,
so it's redundant rcu_read_lock(), and slower the fast path a little.
Lai.
prev parent reply other threads:[~2008-11-22 3:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-21 8:49 [PATCH] cpuset: rcu_read_lock() to protect task_cs() even we don't dereference to task_cs()'s return value Lai Jiangshan
2008-11-21 19:05 ` Paul Menage
2008-11-21 19:07 ` Paul Menage
2008-11-22 3:01 ` Lai Jiangshan [this message]
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