Re: [PATCH 2/2] blk-mq: convert WARN_ON in __blk_mq_run_hw_queue to printk

Jens Axboe
2018-01-17T16:07:44Z

On 1/17/18 9:05 AM, Christian Borntraeger wrote:
>
>
> On 01/17/2018 04:46 PM, Jens Axboe wrote:
>> On 1/17/18 5:34 AM, Ming Lei wrote:
>>> We know this WARN_ON is harmless and the stack trace isn't useful too,
>>> so convert it to printk(), and avoid to confuse people.
>>
>> I disagree, it is useful to know the exact path it happened from,
>> in case it's a valid warning. It could be an inline run and
>> we screwed up the logic, or it could be from a workqueue and
>> the reason would be entirely different.
>
> Then add a dump_stack or whatever, but WARN_ON does have fatal effects
> for some setups. If it can happen then WARN_ON is just wrong.

dump_stack() is fine - and the intent is for it to never happen, it
would be nice to close those holes so we're only catching cases that
are due to bad code.

--
Jens Axboe