From: Andrew Morton <akpm@linux-foundation.org>
To: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
linux-kernel@vger.kernel.org, Tejun Heo <tj@kernel.org>,
Andrew Vagin <avagin@openvz.org>,
Serge Hallyn <serge.hallyn@canonical.com>,
Pavel Emelyanov <xemul@parallels.com>,
Vasiliy Kulikov <segoon@openwall.com>
Subject: Re: [rfc 2/3] fs, proc: Introduce the Children: line in /proc/<pid>/status
Date: Thu, 1 Dec 2011 13:29:11 -0800 [thread overview]
Message-ID: <20111201132911.e20f1fa3.akpm@linux-foundation.org> (raw)
In-Reply-To: <20111201095434.GR14515@moon>
On Thu, 1 Dec 2011 13:54:34 +0400
Cyrill Gorcunov <gorcunov@gmail.com> wrote:
> +int proc_pid_children(struct seq_file *m, struct pid_namespace *ns,
> + struct pid *pid, struct task_struct *task)
> +{
> + struct task_struct *c;
> +
> + read_lock(&tasklist_lock);
> + list_for_each_entry(c, &task->children, sibling)
> + seq_printf(m, " %d", pid_nr_ns(task_pid(c), ns));
> + read_unlock(&tasklist_lock);
> + seq_putc(m, '\n');
> +
> + return 0;
> +}
That's a potentially very long hold time for tasklist_lock, and
userspace can invoke this at a high frequency. Not good.
I think this can all be done under rcu_read_lock() with
list_for_each_entry_rcu().
next prev parent reply other threads:[~2011-12-01 21:29 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-29 19:12 [rfc 0/3] A small bundle in a sake of checkpoint/restore Cyrill Gorcunov
2011-11-29 19:12 ` [rfc 1/3] fs, proc: Add start_data, end_data, start_brk members to /proc/$pid/stat Cyrill Gorcunov
2011-11-29 20:06 ` Kees Cook
2011-12-02 0:24 ` Alexey Dobriyan
2011-12-02 7:28 ` Cyrill Gorcunov
2011-12-02 19:23 ` Kees Cook
2011-12-02 19:28 ` Cyrill Gorcunov
2011-11-29 20:32 ` Serge Hallyn
2011-11-30 5:04 ` KAMEZAWA Hiroyuki
2011-11-29 19:12 ` [rfc 2/3] fs, proc: Introduce the Children: line in /proc/<pid>/status Cyrill Gorcunov
2011-11-30 5:00 ` KAMEZAWA Hiroyuki
2011-11-30 6:05 ` Cyrill Gorcunov
2011-12-01 9:54 ` Cyrill Gorcunov
2011-12-01 15:43 ` Tejun Heo
2011-12-01 15:53 ` Cyrill Gorcunov
2011-12-01 16:07 ` Tejun Heo
2011-12-01 21:29 ` Andrew Morton [this message]
2011-12-01 21:38 ` Cyrill Gorcunov
2011-12-02 0:40 ` KAMEZAWA Hiroyuki
2011-12-02 12:41 ` Pedro Alves
2011-12-02 12:43 ` Pavel Emelyanov
2011-12-02 12:45 ` Cyrill Gorcunov
2011-12-02 13:10 ` Pedro Alves
2011-12-02 13:40 ` Pedro Alves
2011-12-02 12:58 ` Pedro Alves
2011-12-02 13:16 ` Pavel Emelyanov
2011-12-02 13:44 ` Pedro Alves
2011-12-02 13:52 ` Pavel Emelyanov
2011-12-02 14:00 ` Pedro Alves
2011-12-02 14:17 ` Pavel Emelyanov
2011-12-02 14:25 ` Pedro Alves
2011-12-02 14:37 ` Pavel Emelyanov
2011-12-02 14:45 ` Pedro Alves
2011-11-29 19:12 ` [rfc 3/3] prctl: Add PR_SET_MM codes to tune up mm_struct entires Cyrill Gorcunov
2011-11-29 20:19 ` Kees Cook
2011-11-29 20:29 ` Cyrill Gorcunov
2011-11-29 20:37 ` Cyrill Gorcunov
2011-11-29 20:40 ` Kees Cook
2011-11-29 20:47 ` Cyrill Gorcunov
2011-11-30 17:37 ` Cyrill Gorcunov
2011-11-30 18:10 ` Kees Cook
2011-11-30 18:23 ` Cyrill Gorcunov
2011-11-30 21:06 ` Cyrill Gorcunov
2011-12-07 12:27 ` Cyrill Gorcunov
2011-12-07 22:43 ` Andrew Morton
2011-12-08 7:07 ` Cyrill Gorcunov
2011-12-08 7:15 ` Andrew Morton
2011-12-08 7:30 ` Cyrill Gorcunov
2011-11-29 20:37 ` Kees Cook
2011-11-29 20:49 ` Serge Hallyn
2011-11-29 20:55 ` Cyrill Gorcunov
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