linux-kernel - Re: backlight: oops in __mutex_lock_slowpath during head /sys/class/graphics/fb0/* in 2.6.18

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Message-Id: <20060921123742.ec225cc2.akpm@osdl.org>
Date:	Thu, 21 Sep 2006 12:37:42 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Olaf Hering <olaf@...fle.de>
Cc:	linux-kernel@...r.kernel.org,
	linux-fbdev-devel@...ts.sourceforge.net,
	"Antonino A. Daplas" <adaplas@....net>,
	Daniel R Thompson <daniel.thompson@...com>,
	Michael Hanselmann <linux-kernel@...smi.ch>,
	Jon Smirl <jonsmirl@...il.com>
Subject: Re: backlight: oops in __mutex_lock_slowpath during head
 /sys/class/graphics/fb0/* in 2.6.18

On Thu, 21 Sep 2006 14:19:52 +0200
Olaf Hering <olaf@...fle.de> wrote:

> The bl_curve code has some room for improvement.
> 
> ...
> <6>Monitor sense value = 0x60b
> <6>using video mode 13 and color mode 0.
> <4>Console: switching to colour frame buffer device 104x39
> <6>fb0: valkyrie frame buffer device
> ...
> 
> inst-sys:~ # cat /proc/fb
> 0 valkyrie
> inst-sys:~ # l /sys/class/graphics/fb0/
> total 0
> drwxr-xr-x 2 root root    0 Sep 21 11:54 ./
> drwxr-xr-x 4 root root    0 Sep 21 11:53 ../
> -rw-r--r-- 1 root root 4096 Sep 21 12:15 bits_per_pixel
> -rw-r--r-- 1 root root 4096 Sep 21 12:15 bl_curve
> -rw-r--r-- 1 root root 4096 Sep 21 12:15 blank
> -rw-r--r-- 1 root root 4096 Sep 21 12:15 console
> -rw-r--r-- 1 root root 4096 Sep 21 12:15 cursor
> -r--r--r-- 1 root root 4096 Sep 21 12:15 dev
> -rw-r--r-- 1 root root 4096 Sep 21 12:15 mode
> -rw-r--r-- 1 root root 4096 Sep 21 12:15 modes
> -r--r--r-- 1 root root 4096 Sep 21 12:15 name
> -rw-r--r-- 1 root root 4096 Sep 21 12:15 pan
> -rw-r--r-- 1 root root 4096 Sep 21 12:15 rotate
> -rw-r--r-- 1 root root 4096 Sep 21 12:15 state
> -r--r--r-- 1 root root 4096 Sep 21 12:15 stride
> lrwxrwxrwx 1 root root    0 Sep 21 12:15 subsystem -> ../../../class/graphics/
> --w------- 1 root root 4096 Sep 21 12:15 uevent
> -rw-r--r-- 1 root root 4096 Sep 21 12:15 virtual_size
> inst-sys:~ # head /sys/class/graphics/fb0/*
> ==> /sys/class/graphics/fb0/bits_per_pixel <==
> 8
> 
> ==> /sys/class/graphics/fb0/bl_curve <==
> Segmentation fault
> inst-sys:~ # dmesg
> valkyriefb: vmode 13 does not support cmode 1.
> Unable to handle kernel paging request for data at address 0x00000000
> Faulting instruction address: 0xc02c7bd8
> Oops: Kernel access of bad area, sig: 11 [#1]
> 
> Modules linked in: tulip mesh cpufreq_ondemand loop nfs nfs_acl lockd sunrpc sg st sd_mod sr_mod scsi_mod ide_cd cdrom
> NIP: C02C7BD8 LR: C0170EBC CTR: C0170E90
> REGS: c4209db0 TRAP: 0300   Not tainted  (2.6.18-rc7-git1-2-default)
> MSR: 00009032 <EE,ME,IR,DR>  CR: 28042488  XER: 00000000
> DAR: 00000000, DSISR: 22000000
> TASK = c7fc8190[2853] 'head' THREAD: c4208000
> GPR00: C4209E6C C4209E60 C7FC8190 C0B77614 C41D5000 C41D5000 00000000 00008000
> GPR08: 00000000 C0B77618 00000000 00000000 00000000 100200C8 10020000 00000001
> GPR16: 10006D08 7FDF9B3C 100A0000 10080000 00000003 7FDF9CAB C4209F20 C2FCDC78
> GPR24: C038BC14 C01EF568 7FDF7858 C41D5000 C0B77614 C0B77400 C7FC8190 C0B77614
> NIP [C02C7BD8] __mutex_lock_slowpath+0x2c/0xa4
> LR [C0170EBC] show_bl_curve+0x2c/0xa0
> Call Trace:  
> [C4209E60] [C02C7A54] mutex_lock+0x18/0x5c (unreliable)
> [C4209E80] [C0170EBC] show_bl_curve+0x2c/0xa0
> [C4209EB0] [C01EF594] class_device_attr_show+0x2c/0x44
> [C4209EC0] [C00CC3BC] sysfs_read_file+0xb8/0x204
> [C4209EF0] [C0083FE4] vfs_read+0xec/0x1c8
> [C4209F10] [C0084444] sys_read+0x4c/0x8c
> [C4209F40] [C00125F8] ret_from_syscall+0x0/0x40
> --- Exception: c01 at 0xff589f8
>     LR = 0x100045e0
> Instruction dump:
> 4e800020 9421ffe0 7c0802a6 39230004 bfc10018 7c7f1b78 7c5e1378 90010024
> 3801000c 9121000c 81690004 90090004 <900b0000> 91610010 90410014 3800ffff
> 

cc's added.

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