Don Zickus <dzic...@redhat.com> writes:
> On Thu, Oct 27, 2011 at 02:43:22PM -0400, Jeff Moyer wrote:
>> >> This doesn't look like the same problem. Here we've got BUG: scheduling
>> >> while atomic. If it was the bug fixed by the above commits, then you
>> >> would hit a BUG_ON. I would start looking at the btrfs bits to see if
>> >> they're holding any locks in this code path.
>> >
>> > Ignore that one and move to IMG_0350.IMG. 'scheduling while atomic' is
>> > just noise. Besides Mike and Vivek told me to blame you for not pushing
>> > Jens harder on these fixes. :-)))))
>>
>> I'm looking at 0355, which shows the very top of the trace, and that
>> says BUG: scheduling while atomic. So the problem reported here *is*
>> different from the one fixed by the above two commits. In fact, I don't
>> see evidence of the multipath + flush issue in any of these pictures.
>
> You have to ignore the 'schedule while atomic' thing it is just a
>
> printk("BUG: scheduling while atomic"), it is _not_ a BUG(). :-)
> (hint read kernel/sched.c::__schedule_bug)
>
> I see those messages all the time, it really should be a WARN and not a
> misleading BUG, but whatever.
>
> His machine died because the NMI watchdog detected a lockup. The lockup
> was because in blk_insert_cloned_request(), spin_lock_irqsave disabled
> interrupts and spun forever waiting on the q->queue_lock (IMG_0350.JPG).
>
> Mike and Vivek both said that is what you fixed for 3.2. They also said
> the only caller of blk_insert_cloned_request() is multipath, hence that
> argument. I'll cc them. Or maybe I can have them walk over to your cube.
> :-)
Well then they know more than I do. The bug I fixed would not result in
infinite spinning on the queue lock. It resulted in a BUG_ON in
blk_insert_flush, since req->bio was NULL. So again, I really don't see
how this is related. We could put this all to rest by asking the victim
to try out those two patches.
Cheers,
Jeff
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