From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: on CONFIG_MM_OWNER=y, kernel panic is possible.
Date: Tue, 06 May 2008 11:18:05 +0530 [thread overview]
Message-ID: <481FF115.8030503@linux.vnet.ibm.com> (raw)
In-Reply-To: <20080506142255.AC5D.KOSAKI.MOTOHIRO@jp.fujitsu.com>
KOSAKI Motohiro wrote:
> on CONFIG_MM_OWNER=y (that is automatically turned on by mem-cgroup),
> kernel panic is possible by following scenario in mm_update_next_owner().
>
> 1. mm_update_next_owner() is called.
> 2. found caller task in do_each_thread() loop.
> 3. thus, BUG_ON(c == p) is true, it become kernel panic.
>
> end up, We should left out current task.
>
>
That is not possible. If you look at where mm_update_next_owner() is called
from, we call it from
exit_mm() and exec_mmap()
In both cases, we ensure that the task's mm has changed (to NULL and the new mm
respectively), before we call mm_update_next_owner(), hence c->mm can never be
equal to p->mm.
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
WARNING: multiple messages have this Message-ID (diff)
From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: on CONFIG_MM_OWNER=y, kernel panic is possible.
Date: Tue, 06 May 2008 11:18:05 +0530 [thread overview]
Message-ID: <481FF115.8030503@linux.vnet.ibm.com> (raw)
In-Reply-To: <20080506142255.AC5D.KOSAKI.MOTOHIRO@jp.fujitsu.com>
KOSAKI Motohiro wrote:
> on CONFIG_MM_OWNER=y (that is automatically turned on by mem-cgroup),
> kernel panic is possible by following scenario in mm_update_next_owner().
>
> 1. mm_update_next_owner() is called.
> 2. found caller task in do_each_thread() loop.
> 3. thus, BUG_ON(c == p) is true, it become kernel panic.
>
> end up, We should left out current task.
>
>
That is not possible. If you look at where mm_update_next_owner() is called
from, we call it from
exit_mm() and exec_mmap()
In both cases, we ensure that the task's mm has changed (to NULL and the new mm
respectively), before we call mm_update_next_owner(), hence c->mm can never be
equal to p->mm.
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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next prev parent reply other threads:[~2008-05-06 5:49 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-06 5:40 on CONFIG_MM_OWNER=y, kernel panic is possible KOSAKI Motohiro
2008-05-06 5:40 ` KOSAKI Motohiro
2008-05-06 5:48 ` Balbir Singh [this message]
2008-05-06 5:48 ` Balbir Singh
2008-05-06 6:03 ` KOSAKI Motohiro
2008-05-06 6:03 ` KOSAKI Motohiro
2008-05-06 6:18 ` KOSAKI Motohiro
2008-05-06 6:18 ` KOSAKI Motohiro
2008-05-06 6:28 ` Balbir Singh
2008-05-06 6:28 ` Balbir Singh
2008-05-06 6:43 ` KOSAKI Motohiro
2008-05-06 6:43 ` KOSAKI Motohiro
2008-05-07 3:37 ` Paul Menage
2008-05-07 3:37 ` Paul Menage
2008-05-07 23:55 ` [PATCH] on CONFIG_MM_OWNER=y, kernel panic is possible. take2 KOSAKI Motohiro
2008-05-07 23:55 ` KOSAKI Motohiro
2008-05-08 13:53 ` Balbir Singh
2008-05-08 13:53 ` Balbir Singh
2008-05-06 6:32 ` on CONFIG_MM_OWNER=y, kernel panic is possible Balbir Singh
2008-05-06 6:32 ` Balbir Singh
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