linux-kernel - Re: General protection fault with use_blk

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Date:   Wed, 28 Mar 2018 20:13:08 -0700
From:   "Zephaniah E. Loss-Cutler-Hull" <warp@...allh.com>
To:     Jens Axboe <axboe@...nel.dk>,
        "Zephaniah E. Loss-Cutler-Hull" <warp-spam_kernel@...allh.com>,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-scsi@...r.kernel.org
Subject: Re: General protection fault with use_blk_mq=1.

On 03/28/2018 06:02 PM, Jens Axboe wrote:
> On 3/28/18 5:03 PM, Zephaniah E. Loss-Cutler-Hull wrote:
>> 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:
>>

>>
>> 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.

Regards,
Zephaniah E. Loss-Cutler-Hull.



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