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From: "Denys Fedoryshchenko" <denys@visp.net.lb>
To: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: linux-kernel@vger.kernel.org, peterz@infradead.org
Subject: Re: 2.6.24-rc7 to 2.6.24-rc8 possible regression
Date: Tue, 22 Jan 2008 13:10:02 +0200
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No, i am using vanilla kernel. It is one of production machines, and as i 
know screen is not using epoll.

I will try to apply on all my production machines this patch. Sorry if it is 
related.

On Mon, 21 Jan 2008 23:45:40 +0100, Stefan Richter wrote
> Denys Fedoryshchenko wrote:
> > After running screen found in dmesg. It was not happening before.
> > 
> > [625138.248257]
> > [625138.248260] =============================================
> > [625138.248542] [ INFO: possible recursive locking detected ]
> > [625138.248686] 2.6.24-rc8-devel #2
> > [625138.248821] ---------------------------------------------
> > [625138.248963] screen/18164 is trying to acquire lock:
> > [625138.249101]  (&q->lock){++..}, at: [<c01175ff>] __wake_up+0x15/0x42
> > [625138.249454]
> > [625138.249456] but task is already holding lock:
> > [625138.249724]  (&q->lock){++..}, at: [<c01175ff>] __wake_up+0x15/0x42
> > [625138.250073]
> > [625138.250075] other info that might help us debug this:
> > [625138.250343] 2 locks held by screen/18164:
> > [625138.250477]  #0:  (&tty->atomic_read_lock){--..}, at: [<c0231a6c>] 
> > read_chan+0x18f/0x50b
> > [625138.250960]  #1:  (&q->lock){++..}, at: [<c01175ff>] __wake_up+0x15/
0x42
> > [625138.251356]
> > [625138.251357] stack backtrace:
> > [625138.251623] Pid: 18164, comm: screen Not tainted 2.6.24-rc8-devel #2
> > [625138.251764]  [<c0105e84>] show_trace_log_lvl+0x1a/0x2f
> > [625138.251959]  [<c010682c>] show_trace+0x12/0x14
> > [625138.252150]  [<c0107123>] dump_stack+0x6c/0x72
> > [625138.252338]  [<c01384c0>] __lock_acquire+0x172/0xb8c
> > [625138.252533]  [<c01392a7>] lock_acquire+0x5f/0x78
> > [625138.252725]  [<c032afa7>] _spin_lock_irqsave+0x34/0x44
> > [625138.252920]  [<c01175ff>] __wake_up+0x15/0x42
> > [625138.253108]  [<c0186a16>] ep_poll_safewake+0x8e/0xbf
> > [625138.253300]  [<c01876df>] ep_poll_callback+0x9f/0xac
> > [625138.253491]  [<c0115d36>] __wake_up_common+0x32/0x5c
> > [625138.253688]  [<c011761b>] __wake_up+0x31/0x42
> > [625138.253878]  [<c022c803>] tty_wakeup+0x4f/0x54
> > [625138.254070]  [<c0232c7c>] pty_unthrottle+0x15/0x21
> > [625138.254258]  [<c022ffe3>] check_unthrottle+0x2e/0x30
> > [625138.254445]  [<c0231cf4>] read_chan+0x417/0x50b
> > [625138.254633]  [<c022ec67>] tty_read+0x66/0xac
> > [625138.254819]  [<c01628dc>] vfs_read+0x8e/0x117
> > [625138.255004]  [<c0162d10>] sys_read+0x3d/0x61
> > [625138.255190]  [<c0104dee>] sysenter_past_esp+0x5f/0xa5
> > [625138.255376]  =======================
> 
> Do you have Peter's lockdep annotation patch for epoll applied?
> http://lkml.org/lkml/2008/1/13/84
> -- 
> Stefan Richter
> -=====-==--- ---= =-=-=
> http://arcgraph.de/sr/


--
Denys Fedoryshchenko
Technical Manager
Virtual ISP S.A.L.