From: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
To: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Dave Jones <davej-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Linux Kernel
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Alexander Viro
<viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH 1/1] do not abuse ->cred_guard_mutex in threadgroup_lock()
Date: Mon, 11 Mar 2013 09:50:55 +0800 [thread overview]
Message-ID: <513D387F.6060101@huawei.com> (raw)
In-Reply-To: <20130309200106.GB8149-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
On 2013/3/10 4:01, Oleg Nesterov wrote:
> threadgroup_lock() takes signal->cred_guard_mutex to ensure that
> thread_group_leader() is stable. This doesn't look nice, the scope
> of this lock in do_execve() is huge.
>
> And as Dave pointed out this can lead to deadlock, we have the
> following dependencies:
>
> do_execve: cred_guard_mutex -> i_mutex
> cgroup_mount: i_mutex -> cgroup_mutex
> attach_task_by_pid: cgroup_mutex -> cred_guard_mutex
>
> Change de_thread() to take threadgroup_change_begin() around the
> switch-the-leader code and change threadgroup_lock() to avoid
> ->cred_guard_mutex.
>
> Note that de_thread() can't sleep with ->group_rwsem held, this
> can obviously deadlock with the exiting leader if the writer is
> active, so it does threadgroup_change_end() before schedule().
>
> Reported-by: Dave Jones <davej-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Acked-by: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
WARNING: multiple messages have this Message-ID (diff)
From: Li Zefan <lizefan@huawei.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>, Dave Jones <davej@redhat.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
<cgroups@vger.kernel.org>
Subject: Re: [PATCH 1/1] do not abuse ->cred_guard_mutex in threadgroup_lock()
Date: Mon, 11 Mar 2013 09:50:55 +0800 [thread overview]
Message-ID: <513D387F.6060101@huawei.com> (raw)
In-Reply-To: <20130309200106.GB8149@redhat.com>
On 2013/3/10 4:01, Oleg Nesterov wrote:
> threadgroup_lock() takes signal->cred_guard_mutex to ensure that
> thread_group_leader() is stable. This doesn't look nice, the scope
> of this lock in do_execve() is huge.
>
> And as Dave pointed out this can lead to deadlock, we have the
> following dependencies:
>
> do_execve: cred_guard_mutex -> i_mutex
> cgroup_mount: i_mutex -> cgroup_mutex
> attach_task_by_pid: cgroup_mutex -> cred_guard_mutex
>
> Change de_thread() to take threadgroup_change_begin() around the
> switch-the-leader code and change threadgroup_lock() to avoid
> ->cred_guard_mutex.
>
> Note that de_thread() can't sleep with ->group_rwsem held, this
> can obviously deadlock with the exiting leader if the writer is
> active, so it does threadgroup_change_end() before schedule().
>
> Reported-by: Dave Jones <davej@redhat.com>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Li Zefan <lizefan@huawei.com>
next prev parent reply other threads:[~2013-03-11 1:50 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-06 22:36 lockdep trace from prepare_bprm_creds Dave Jones
[not found] ` <20130306223657.GA7392-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2013-03-07 17:25 ` Oleg Nesterov
2013-03-07 17:25 ` Oleg Nesterov
2013-03-07 18:01 ` Tejun Heo
[not found] ` <20130307180139.GD29601-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2013-03-07 18:03 ` Tejun Heo
2013-03-07 18:03 ` Tejun Heo
[not found] ` <20130307180332.GE29601-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2013-03-07 19:12 ` Oleg Nesterov
2013-03-07 19:12 ` Oleg Nesterov
[not found] ` <20130307191242.GA18265-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2013-03-07 19:38 ` Tejun Heo
2013-03-07 19:38 ` Tejun Heo
[not found] ` <20130307193820.GB3209-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2013-03-09 2:11 ` Li Zefan
2013-03-09 2:11 ` Li Zefan
[not found] ` <513A9A67.60909-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-03-09 3:29 ` Tejun Heo
2013-03-09 3:29 ` Tejun Heo
[not found] ` <20130309032936.GT14556-9pTldWuhBndy/B6EtB590w@public.gmane.org>
2013-03-09 7:47 ` Li Zefan
2013-03-09 7:47 ` Li Zefan
[not found] ` <513AE918.7020704-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-03-09 20:00 ` [PATCH 0/1] do not abuse ->cred_guard_mutex in threadgroup_lock() Oleg Nesterov
2013-03-09 20:00 ` Oleg Nesterov
2013-03-09 20:01 ` [PATCH 1/1] " Oleg Nesterov
[not found] ` <20130309200106.GB8149-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2013-03-09 20:15 ` Tejun Heo
2013-03-09 20:15 ` Tejun Heo
2013-03-11 1:50 ` Li Zefan [this message]
2013-03-11 1:50 ` Li Zefan
[not found] ` <20130309200046.GA8149-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2013-03-21 16:21 ` [PATCH] " Oleg Nesterov
2013-03-21 16:21 ` Oleg Nesterov
[not found] ` <20130321162138.GA21859-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2013-03-21 22:06 ` Andrew Morton
2013-03-21 22:06 ` Andrew Morton
[not found] ` <20130321150626.a7934d989fb80d835fa92255-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2013-03-22 13:20 ` Oleg Nesterov
2013-03-22 13:20 ` Oleg Nesterov
2013-03-19 22:02 ` [PATCH cgroup/for-3.10] cgroup: make cgroup_mutex outer to threadgroup_lock Tejun Heo
[not found] ` <20130319220246.GR3042-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2013-03-20 0:58 ` Li Zefan
2013-03-20 0:58 ` Li Zefan
2013-03-20 15:03 ` Tejun Heo
[not found] ` <20130320150351.GW3042-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2013-03-20 18:35 ` Oleg Nesterov
2013-03-20 18:35 ` Oleg Nesterov
[not found] ` <20130320183523.GA29365-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2013-03-20 18:42 ` Tejun Heo
2013-03-20 18:42 ` Tejun Heo
[not found] ` <CAOS58YPxGXt+iq1GZ4hryqm1Z_p+r7eRRC7ruUDDd=LQrWtAxg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-03-21 16:17 ` Oleg Nesterov
2013-03-21 16:17 ` Oleg Nesterov
2013-03-07 18:21 ` lockdep trace from prepare_bprm_creds Tejun Heo
2013-03-07 18:21 ` Tejun Heo
[not found] ` <20130307182140.GF29601-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2013-03-07 18:32 ` Oleg Nesterov
2013-03-07 18:32 ` Oleg Nesterov
[not found] ` <20130307183213.GA18022-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2013-03-07 19:33 ` Tejun Heo
2013-03-07 19:33 ` Tejun Heo
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