Re: [PATCH] sbitmap: silence bogus lockdep IRQ warning

[Jens Axboe <axboe@kernel.dk>]

On 12/9/18 9:58 AM, Guenter Roeck wrote:
> On Sun, Dec 09, 2018 at 07:26:47AM -0700, Jens Axboe wrote:
>>
>> Ming that lockdep spews the following trace. What this essentially says
>> is that the sbitmap swap_lock was used inconsistently in IRQ enabled
>> and disabled context, and that is usually indicative of a bug that will
>> cause a deadlock.
>>
>> For this case, it's a false positive. The swap_lock is used from process
>> context only, when we swap the bits in the word and cleared mask. We
>> also end up doing that when we are getting a driver tag, from the
>> blk_mq_mark_tag_wait(), and from there we hold the waitqueue lock with
>> IRQs disabled. However, this isn't from an actual IRQ, it's still
>> process context.
>>
>> Mark the swap_lock as not needing validation to silence this warning.
>>
> 
> checkpatch says:
> 
> $ scripts/checkpatch.pl jens2
> ERROR: lockdep_no_validate class is reserved for device->mutex.
> #357: FILE: lib/sbitmap.c:68:
> +		lockdep_set_novalidate_class(&sb->map[i].swap_lock);
> 
> ... which I think explains the warning I am seeing with this patch applied. 

Try the other patch I sent out earlier, that should work.

-- 
Jens Axboe