linux-kernel - (WARNING) possible deadlock in del_timer_sync, called from fbcon_del_cursor

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Date:	Mon, 28 Feb 2011 15:41:07 +0100
From:	Clemens Ladisch <clemens@...isch.de>
To:	linux-fbdev@...r.kernel.org
CC:	linux-kernel@...r.kernel.org
Subject: (WARNING) possible deadlock in del_timer_sync, called from fbcon_del_cursor_timer

While using the FB console, I tried to change the console log level
with SysRq, and got this warning that del_timer_sync() is used in
an interrupt handler:

SysRq :
------------[ cut here ]------------
WARNING: at kernel/timer.c:983 del_timer_sync+0x93/0xae()
Hardware name: System Product Name
Modules linked in: soundcore firewire_ohci firewire_core ohci_hcd ehci_hcd
Pid: 0, comm: kworker/0:1 Not tainted 2.6.38-rc6+ #235
Call Trace:
 <IRQ>  [<ffffffff8103a6df>] ? warn_slowpath_common+0x80/0x98
 [<ffffffff8103a70c>] ? warn_slowpath_null+0x15/0x17
 [<ffffffff810452a7>] ? del_timer_sync+0x93/0xae
 [<ffffffff81045214>] ? del_timer_sync+0x0/0xae
 [<ffffffff8120725a>] ? fbcon_del_cursor_timer+0x32/0x3d
 [<ffffffff812077f0>] ? fbcon_cursor+0x9a/0x152
 [<ffffffff8125fd84>] ? hide_cursor+0x2c/0x7d
 [<ffffffff8126022b>] ? vt_console_print+0xd9/0x2f7
 [<ffffffff8103a891>] ? __call_console_drivers+0x67/0x79
 [<ffffffff8103a8fc>] ? _call_console_drivers+0x59/0x5d
 [<ffffffff8103ae3e>] ? console_unlock+0x160/0x1ce
 [<ffffffff8103b44a>] ? vprintk+0x358/0x38e
 [<ffffffff81466199>] ? printk+0x3c/0x3e
 [<ffffffff812594ce>] ? __handle_sysrq+0x23/0x157
 [<ffffffff812594f0>] ? __handle_sysrq+0x45/0x157
 [<ffffffff81259758>] ? sysrq_filter+0x116/0x17b
 [<ffffffff8139b9c5>] ? input_pass_event+0xbe/0x111
 [<ffffffff8139b907>] ? input_pass_event+0x0/0x111
 [<ffffffff8139cfb4>] ? input_handle_event+0x42a/0x439
 [<ffffffff8139d0e9>] ? input_event+0x5b/0x7a
 [<ffffffff813a37f3>] ? atkbd_interrupt+0x50f/0x5e0
 [<ffffffff8139735c>] ? serio_interrupt+0x40/0x7c
 [<ffffffff81398647>] ? i8042_interrupt+0x289/0x2a3
 [<ffffffff8107ae98>] ? handle_IRQ_event+0x20/0xa8
 [<ffffffff8107cd68>] ? handle_edge_irq+0x103/0x14f
 [<ffffffff81004a2b>] ? handle_irq+0x83/0x8c
 [<ffffffff81004067>] ? do_IRQ+0x48/0xaf
 [<ffffffff81469a93>] ? ret_from_intr+0x0/0x13
 <EOI>  [<ffffffff8105d49e>] ? tick_broadcast_oneshot_control+0x1a/0xfb
 [<ffffffff810098cc>] ? default_idle+0x27/0x43
 [<ffffffff810098ce>] ? default_idle+0x29/0x43
 [<ffffffff810098cc>] ? default_idle+0x27/0x43
 [<ffffffff81009a33>] ? c1e_idle+0xcd/0xf4
 [<ffffffff810012e5>] ? cpu_idle+0x5f/0x96
 [<ffffffff81462b7c>] ? start_secondary+0x1e3/0x1e5
---[ end trace 80565a42945fc993 ]---
Changing Loglevel
Loglevel set to 3


To add insult to injury, my cursor is configured not to blink.


Regards,
Clemens
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