sysctl -a causes kernel trap 12

[Xin Li]

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On 01/07/13 16:02, Konstantin Belousov wrote:
> On Mon, Jan 07, 2013 at 03:54:23PM -0800, Xin Li wrote:
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>> 
>> Hi,
>> 
>> I've recently (by mid-December I think) noticed that sysctl -a
>> can sometimes cause kernel trap 12.  Tried enabling INVARIANTS
>> and the problem mysteriously disappeared.  After some experiments
>> on this, it seems that this can be triggered by sysctl -a but the
>> system have an 1 in 10 chance to survive.  When INVARIANTS is
>> enabled however, I can not trigger the panic.  "sysctl hw"
>> triggers the panic sometimes, but not always.
>> 
>> Do anybody have clue on this?  The system hangs hard when it
>> panics so kernel debugger won't work.  When it panics, the fault
>> instruction pointer is always 0x20:0xffffffff808d61c9, which is 
>> sys/kern/subr_turnstile.c:297:
>> 
>>> /* Resort td on the list if needed. */ if 
>>> (!turnstile_adjust_thread(ts, td)) {
>>> mtx_unlock_spin(&ts->ts_lock); // 297 // return; }
>> 
>> This sounds like a race condition but I haven't yet able to track
>> it down...
> 
> Could you try to isolate the sub-leaf under hw which causes the
> panic ? Just shot in the dark, do you have Intel GPU gemified
> driver loaded ?

It seems that it was not hw itself that causes the problem (I thought
about isolating to sub-leaf and at one point believed it was
hw.acpi.battery but doing so repeatedly doesn't panic the system, with
or without INVARIANTS; doing 'sysctl hw' sometimes causes panic but
not always).

The laptop is running nVidia but it's using i7-3610QM which does have
Intel GPU, but I have not loaded drm2.ko and the panic is reproducible
in single user mode.

Cheers,
- -- 
Xin LI <delphij at delphij.net>    https://www.delphij.net/
FreeBSD - The Power to Serve!           Live free or die
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