From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: penguin-kernel@I-love.SAKURA.ne.jp
Cc: john.stultz@linaro.org, tytso@mit.edu, mina86@mina86.com,
jirislaby@gmail.com, rientjes@google.com, dave@linux.vne,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/3] v4 Improve task->comm locking situation
Date: Wed, 18 May 2011 13:10:44 +0900 [thread overview]
Message-ID: <4DD346C4.5030200@jp.fujitsu.com> (raw)
In-Reply-To: <201105180316.p4I3G6f2094560@www262.sakura.ne.jp>
(2011/05/18 12:16), Tetsuo Handa wrote:
> What about replacing
> char comm[TASK_COMM_LEN];
> with
> char *rcu_commname;
> and switching it atomically using RCU?
>
> Advantages:
> Readers can use RCU read lock rather than spinlock.
> Makes task_struct smaller.
>
> Disadvantages:
> Need to allocate TASK_COMM_LEN bytes upon dup_task_struct() and set_task_comm().
> Need to rewrite all task_struct.comm readers (steps shown below).
>
> Steps to rewrite task_struct.comm readers
>
> (1) Introduce a temporary accessor (say, task_comm).
>
> #define task_comm(tsk) (tsk)->comm
>
> (2) Rewrite all tsk->comm users to task_comm(tsk).
>
> (3) Replace sizeof(tsk->comm) with TASK_COMM_LEN.
The problem is, they aren't a few. But if you have a enough brave,
you can rewrite all. I'm not against it.
next prev parent reply other threads:[~2011-05-18 4:11 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-16 21:19 John Stultz
2011-05-16 21:19 ` [PATCH 1/3] comm: Introduce comm_lock seqlock to protect task->comm access John Stultz
2011-05-16 22:01 ` Jiri Slaby
2011-05-17 1:47 ` John Stultz
2011-05-18 0:28 ` KOSAKI Motohiro
2011-05-16 21:19 ` [PATCH 2/3] printk: Add %ptc to safely print a task's comm John Stultz
2011-05-16 21:54 ` Jiri Slaby
2011-05-16 23:10 ` John Stultz
2011-05-16 23:56 ` Joe Perches
2011-05-17 0:11 ` John Stultz
2011-05-17 7:21 ` Jiri Slaby
2011-05-18 0:32 ` KOSAKI Motohiro
2011-05-16 21:19 ` [PATCH 3/3] checkpatch.pl: Add check for task comm references John Stultz
2011-05-16 21:29 ` Michal Nazarewicz
2011-05-16 21:34 ` David Rientjes
2011-05-16 23:04 ` Joe Perches
2011-05-16 23:11 ` Michal Nazarewicz
2011-05-16 23:22 ` Joe Perches
2011-05-18 3:16 ` [PATCH 0/3] v4 Improve task->comm locking situation Tetsuo Handa
2011-05-18 4:10 ` KOSAKI Motohiro [this message]
2011-05-18 4:15 ` John Stultz
2011-05-18 5:27 ` Tetsuo Handa
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