Kernel Bug Tracker – Bug 8513
Manually loading snd-powermac causes badness in lib/kref.c:33
Last modified: 2007-09-05 09:41:36 UTC
Most recent kernel where this bug did *NOT* occur: 2.6.20
Hardware Environment: PowerMac G5
Steps to reproduce:
Loading snd-aoa modules.
Original bug report: https://launchpad.net/bugs/115597
Snippet of oops, although this may be after the first oops (hard to tell from
[ 958.083421] ------------[ cut here ]------------
[ 958.083436] Badness at /build/buildd/linux-source-2.6.22-2.6.22/lib/kref.c:33
[ 958.083439] Call Trace:
[ 958.083443] [c00000015d94b320] [c00000000000ff14] .show_stack+0x54/0x1f0
[ 958.083456] [c00000015d94b3d0] [c0000000001bfe3c] .report_bug+0xac/0x150
[ 958.083465] [c00000015d94b460] [c0000000003cfb08]
[ 958.083474] [c00000015d94b510] [c000000000004f0c] program_check_common+0x10c/0x180
[ 958.083480] --- Exception: 700 at .kref_get+0xc/0x30
[ 958.083488] LR = .of_node_get+0x20/0x40
[ 958.083492] [c00000015d94b800] [c0000000000c5a10]
[ 958.083502] [c00000015d94b880] [c000000000048c28] .__pmf_find_function+0x48/0x220
[ 958.083510] [c00000015d94b980] [c000000000048e50] .pmf_find_function+0x50/0xa0
[ 958.083517] [c00000015d94ba20] [c000000000048ec0] .pmf_call_function+0x20/0x60
[ 958.083524] [c00000015d94bab0] [d00000000045ba00] .pmf_get_detect+0x60/0xd0
[ 958.083539] [c00000015d94bb60] [d000000000414400] .detected_get+0x70/0xb0
[ 958.083548] [c00000015d94bbe0] [d0000000003384e4]
[ 958.083579] [c00000015d94bc80] [d00000000033ae34]
[ 958.083595] [c00000015d94bd40] [c000000000149930] .compat_sys_ioctl+0x160/0x4e0
[ 958.083603] [c00000015d94be30] [c0000000000086b4] syscall_exit+0x0/0x40
I've seen this bug myself but it went away when I did these two changes:
(1) upgrade to -rc2
(2) load snd-aoa-i2sbus at boot (/etc/modules)
so now when I load snd-aoa-i2sbus it doesn't happen any more, but I don't know
whether loading it at boot or the kernel upgrade fixed it.
Ben, does it still happen with rc3?
Found out the root cause of this. In prior releases we had snd-powermac added to
/etc/modules, since autoloading didn't work. Removing this allows things to work
properly, with no "badness" backtrace. However, I'd like to get this resolved so
that loading snd-powermac in this way doesn't cause horrible looking errors.
Ah OK, that explains. I guess, however, it's no regression but a remaining
problem since old versions. Could you try the older kernel whether the same
Actually it is a regression. Having this module loaded with 2.6.20 didn't cause
this, and snd-aoa still worked.
And regression or not, it shouldn't cause a crash :)
Thanks for confirmation. Any chance to test 2.6.21?
It's VERY important to know that it's a regression, for finding out the bug...
It seems it did not occur with 2.6.21. Started somewhere around 2.6.22-rc1 or rc2.
If it's due to any change in the aoa driver, there are only a few changes.
Suspicious ones are:
[ALSA] snd-aoa-i2sbus: use MODULE_DEVICE_TABLE instead of plain MODULE_ALIAS
uevent: use add_uevent_var() instead of open coding it
Other changes look pretty harmless.
Could you try to revert one of them?
fixed by commit 41e904dee22066ae7ac3a7f695b2c8bd43ce4e04, the bug wasn't in snd-aoa at all