On 3/28/18 9:13 PM, Zephaniah E. Loss-Cutler-Hull wrote:

On 03/28/2018 06:02 PM, Jens Axboe wrote:

quoted

On 3/28/18 5:03 PM, Zephaniah E. Loss-Cutler-Hull wrote:

quoted

I am not subscribed to any of the lists on the To list here, please CC
me on any replies.

I am encountering a fairly consistent crash anywhere from 15 minutes to
12 hours after boot with scsi_mod.use_blk_mq=1 dm_mod.use_blk_mq=1> 
The crash looks like:

quoted

quoted

Looking through the code, I'd guess that this is dying inside
blkg_rwstat_add, which calls percpu_counter_add_batch, which is what RIP
is pointing at.

Leaving the whole thing here for Paolo - it's crashing off insertion of
a request coming out of SG_IO. Don't think we've seen this BFQ failure
case before.

You can mitigate this by switching the scsi-mq devices to mq-deadline
instead.

I'm thinking that I should also be able to mitigate it by disabling
CONFIG_DEBUG_BLK_CGROUP.

That should remove that entire chunk of code.

Of course, that won't help if this is actually a symptom of a bigger
problem.

Yes, it's not a given that it will fully mask the issue at hand. But
turning off BFQ has a much higher chance of working for you.

This time actually CC'ing Paolo.


-- 
Jens Axboe