# echo 1 > /proc/acpi/video/GFX0/LCD/brightness <1>Unable to handle kernel NULL pointer dereference at virtual address 00000004 printing eip: c022216e *pde = 00000000 Oops: 0000 [#3] PREEMPT Modules linked in: snd_seq snd_intel8x0 snd_ac97_codec snd_pcm snd_timer snd snd _page_alloc ipw2200 ieee80211 ieee80211_crypt CPU: 0 EIP: 0060:[<c022216e>] Not tainted VLI EFLAGS: 00010246 (2.6.11-gentoo-r6) EIP is at acpi_video_device_write_brightness+0x69/0x96 eax: 00000001 ebx: 00000001 ecx: 00000000 edx: 00000000 esi: df47e7c0 edi: 00000002 ebp: b7e69000 esp: dd070f64 ds: 007b es: 007b ss: 0068 Process bash (pid: 6892, threadinfo=dd070000 task=df02d0a0) Stack: 00000a31 00000000 00000002 dc569040 c0159e4c dc569040 b7e69000 00000002 dd070fac dc569040 fffffff7 b7e69000 dd070000 c0159f31 dc569040 b7e69000 00000002 dd070fac 00000000 00000000 00000000 00000001 00000002 c0103119 Call Trace: [<c0159e4c>] vfs_write+0x14c/0x160 [<c0159f31>] sys_write+0x51/0x80 [<c0103119>] sysenter_past_esp+0x52/0x75 Code: 85 c0 ba f2 ff ff ff 75 48 c6 04 3c 00 6a 00 6a 00 53 e8 26 a8 fa ff 83 c4 0c 83 f8 64 89 c3 ba f2 ff ff ff 77 2b 8b 56 1c 31 c9 <3b> 4a 04 7d 1f 8b 42 08 3b 1c 88 75 14 53 56 e8 16 f8 ff ff 5a Reproducible: Always Steps to Reproduce: write someth. into /proc/acpi/video/GFX0/LCD/brightness Actual Results: bash crashes - agetty respawns Expected Results: changing the display-brigthness
Ok, here's how you can help me track this down: Make sure you haven't made any changes to your kernel compilation *without* rebooting into it (i.e. if you have changed stuff in /usr/src/linux, compile it and copy over the new bzImage, reboot, etc). If you have time, it would be useful trying to reproduce this on vanilla-sources-2.6.12_rc3. So, you could install and compile that now, and reboot into it. The interesting line in the oops is this one: EIP is at acpi_video_device_write_brightness+0x69/0x96 Reproduce the oops and check the function and offset again. The interesting part is before the / in the above message, i.e. "acpi_video_device_write_brightness+0x69". It's important that we know the up-to-date offset (0x69 above) of the error. Go into your kernel sources directory, and enable CONFIG_DEBUG_INFO: # cd /usr/src/linux # make menuconfig Kernel hacking ---> [*] Kernel debugging [*] Compile the kernel with debug info Save and exit. Don't recompile *anything*, other than running: # rm drivers/acpi/video.o # make drivers/acpi/video.o Now run gdb on that object (you might need to emerge gdb) # gdb drivers/acpi/video.o At the gdb prompt, run: # list *acpi_video_device_write_brightness+0x69 Note the * prefix, and use the correct offset address if it has changed from 0x69 Please post the full output of the above command to this bug.
If thats too much work you could just report it to http://bugzilla.kernel.org - there may be an obvious fix.
Please reopen when you are able to take up one of the above suggestions. You should also test 2.6.12-rc5 to see if the issue has already been fixed.
