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Date: Wed, 23 May 2012 09:06:22 +0800
Message-ID: <CACVXFVMz_GKHXpzbqt24yY=fHJ6uYZPOcSnKNFHrvbdpWxc7tw@mail.gmail.com>
Subject: Re: 3.4+ tty lockdep trace
From: Ming Lei <tom.leiming@gmail.com>
To: Dave Jones <davej@redhat.com>, Linux Kernel <linux-kernel@vger.kernel.org>,
        Alan Cox <alan@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Hi Dave,

On Wed, May 23, 2012 at 8:26 AM, Dave Jones <davej@redhat.com> wrote:
> From v3.4-4413-gfb09baf
>
> [ ? 43.374948] =============================================
> [ ? 43.374991] [ INFO: possible recursive locking detected ]
> [ ? 43.375035] 3.4.0+ #24 Not tainted
> [ ? 43.375065] ---------------------------------------------
> [ ? 43.375108] sshd/639 is trying to acquire lock:
> [ ? 43.375157] ?(&tty->legacy_mutex){+.+.+.}, at: [<ffffffff81656d57>] tty_lock+0x37/0x80
> [ ? 43.375216]
> [ ? 43.375216] but task is already holding lock:
> [ ? 43.375268] ?(&tty->legacy_mutex){+.+.+.}, at: [<ffffffff81656d57>] tty_lock+0x37/0x80
> [ ? 43.375327]
> [ ? 43.375327] other info that might help us debug this:
> [ ? 43.375378] ?Possible unsafe locking scenario:
> [ ? 43.375378]
> [ ? 43.375425] ? ? ? ?CPU0
> [ ? 43.375447] ? ? ? ?----
> [ ? 43.375471] ? lock(&tty->legacy_mutex);
> [ ? 43.375504] ? lock(&tty->legacy_mutex);
> [ ? 43.375536]
> [ ? 43.375536] ?*** DEADLOCK ***
> [ ? 43.375536]
> [ ? 43.375583] ?May be due to missing lock nesting notation
> [ ? 43.375583]
> [ ? 43.375637] 2 locks held by sshd/639:
> [ ? 43.375675] ?#0: ?(tty_mutex){+.+.+.}, at: [<ffffffff813b0243>] tty_release+0x1c3/0x5d0
> [ ? 43.375740] ?#1: ?(&tty->legacy_mutex){+.+.+.}, at: [<ffffffff81656d57>] tty_lock+0x37/0x80
> [ ? 43.375802]
> [ ? 43.375802] stack backtrace:
> [ ? 43.375841] Pid: 639, comm: sshd Not tainted 3.4.0+ #24
> [ ? 43.375882] Call Trace:
> [ ? 43.377572] ?[<ffffffff810b4604>] __lock_acquire+0x1584/0x1aa0
> [ ? 43.379286] ?[<ffffffff810b51e2>] lock_acquire+0x92/0x1f0
> [ ? 43.380995] ?[<ffffffff81656d57>] ? tty_lock+0x37/0x80
> [ ? 43.382700] ?[<ffffffff816534f1>] mutex_lock_nested+0x71/0x3b0
> [ ? 43.384403] ?[<ffffffff81656d57>] ? tty_lock+0x37/0x80
> [ ? 43.386094] ?[<ffffffff81085521>] ? get_parent_ip+0x11/0x50
> [ ? 43.387794] ?[<ffffffff81656d57>] ? tty_lock+0x37/0x80
> [ ? 43.389480] ?[<ffffffff8165a68d>] ? sub_preempt_count+0x6d/0xd0
> [ ? 43.391176] ?[<ffffffff813b0243>] ? tty_release+0x1c3/0x5d0
> [ ? 43.393003] ?[<ffffffff81656d57>] tty_lock+0x37/0x80
> [ ? 43.394867] ?[<ffffffff81656dc3>] tty_lock_pair+0x23/0x5c
> [ ? 43.396671] ?[<ffffffff813b024e>] tty_release+0x1ce/0x5d0
> [ ? 43.398462] ?[<ffffffff811a765c>] fput+0x12c/0x300
> [ ? 43.400292] ?[<ffffffff811a23a9>] filp_close+0x69/0xa0
> [ ? 43.402084] ?[<ffffffff811a2f2d>] sys_close+0xad/0x1a0
> [ ? 43.403871] ?[<ffffffff8165e652>] system_call_fastpath+0x16/0x1b

We have one patch to address the problem, could you test it from the link below?

        http://marc.info/?l=linux-kernel&m=133765211309247&w=2


Thanks,
-- 
Ming Lei
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