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 1:51 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-06 22:36 lockdep trace from prepare_bprm_creds Dave Jones
2013-03-07 17:25 ` Oleg Nesterov
2013-03-07 18:01 ` Tejun Heo
2013-03-07 18:03 ` Tejun Heo
2013-03-07 19:12 ` Oleg Nesterov
2013-03-07 19:38 ` Tejun Heo
2013-03-09 2:11 ` Li Zefan
2013-03-09 3:29 ` Tejun Heo
2013-03-09 7:47 ` Li Zefan
2013-03-09 20:00 ` [PATCH 0/1] do not abuse ->cred_guard_mutex in threadgroup_lock() Oleg Nesterov
2013-03-09 20:01 ` [PATCH 1/1] " Oleg Nesterov
2013-03-09 20:15 ` Tejun Heo
2013-03-11 1:50 ` Li Zefan [this message]
2013-03-21 16:21 ` [PATCH] " Oleg Nesterov
2013-03-21 22:06 ` Andrew Morton
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
2013-03-20 0:58 ` Li Zefan
2013-03-20 15:03 ` Tejun Heo
2013-03-20 18:35 ` Oleg Nesterov
2013-03-20 18:42 ` Tejun Heo
2013-03-21 16:17 ` Oleg Nesterov
2013-03-07 18:21 ` lockdep trace from prepare_bprm_creds Tejun Heo
2013-03-07 18:32 ` Oleg Nesterov
2013-03-07 19:33 ` Tejun Heo
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