linux-kernel - Re: Linux 2.6.31-rc9

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Date:	Tue, 8 Sep 2009 13:20:03 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 2.6.31-rc9


FYI, i'm getting very (very) rare warnings from the TTY code in this 
place:

[   28.187364] rc.sysinit used greatest stack depth: 5224 bytes left
[   31.422457] Adding 3911816k swap on /dev/sda2.  Priority:-1 extents:1 across:3911816k 
[   32.974830] ssh used greatest stack depth: 5200 bytes left
[   33.115028] ------------[ cut here ]------------
[   33.119518] WARNING: at drivers/char/tty_io.c:1267 __tty_open+0x3ef/0x4c0()
[   33.126588] Hardware name: System Product Name
[   33.130893] Modules linked in:
[   33.133931] Pid: 2494, comm: modprobe Not tainted 2.6.31-rc9-tip-01377-ga8dae3f-dirty #11516
[   33.142329] Call Trace:
[   33.144834]  [<c175ef53>] ? printk+0x23/0x40
[   33.149009]  [<c12e3d9f>] ? __tty_open+0x3ef/0x4c0
[   33.153851]  [<c1049aed>] warn_slowpath_common+0x7d/0xe0
[   33.159061]  [<c12e3d9f>] ? __tty_open+0x3ef/0x4c0
[   33.163866]  [<c1049b71>] warn_slowpath_null+0x21/0x40
[   33.168940]  [<c12e3d9f>] __tty_open+0x3ef/0x4c0
[   33.173558]  [<c12e3e99>] tty_open+0x29/0x50
[   33.177782]  [<c10eb136>] chrdev_open+0x176/0x270
[   33.182458]  [<c10e44d1>] __dentry_open+0x191/0x400
[   33.187345]  [<c10eafc0>] ? chrdev_open+0x0/0x270
[   33.191994]  [<c10e485b>] nameidata_to_filp+0x6b/0x80
[   33.197051]  [<c10f5689>] do_filp_open+0x2c9/0x8f0
[   33.201788]  [<c107a308>] ? put_lock_stats+0x18/0x50
[   33.206749]  [<c107f85c>] ? __lock_release+0x7c/0x1c0
[   33.211755]  [<c1762d55>] ? _spin_unlock+0x35/0x70
[   33.216547]  [<c11012c0>] ? alloc_fd+0xe0/0x110
[   33.221027]  [<c10e4165>] do_sys_open+0x85/0x150
[   33.225642]  [<c10e42c4>] sys_open+0x34/0x60
[   33.229869]  [<c10041a7>] sysenter_do_call+0x12/0x3c
[   33.234830] ---[ end trace 236953f4cdb167e9 ]---
[   33.240764] device: 'vcs7': device_add
[   33.241171] device: 'vcsa7': device_add
[   33.249492] device: 'vcs4': device_add
[   33.250112] device: 'vcsa4': device_add
[   33.260339] device: 'vcs2': device_add

I got it on two systems so far. Config attached (but is probably 
irrelevant). The warnings started in the .31 cycle. They occur every 
1000-2000 random kernels - i.e. every few days.

One sidenote: the system that triggered the most such warnings so 
far is a P4 dual socket HT box - which is always the first one to 
trigger narrow SMP traces. That might (or might not) be relevant.

These warnings were never fatal and my guess is that they are 
ancient, pre-existing races in the TTY code - but wanted to mention 
them here in case they matter.

	Ingo

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