Re: [PATCH 7/8] mq-deadline: add blk-mq adaptation of the deadline IO scheduler

[Jens Axboe]

On 02/02/2017 02:19 AM, Paolo Valente wrote:
> The scheme is clear.  One comment, in case it could make sense and
> avoid more complexity: since put_rq_priv is invoked in two different
> contexts, process or interrupt, I didn't feel so confusing that, when
> put_rq_priv is invoked in the context where the lock cannot be held
> (unless one is willing to pay with irq disabling all the times), the
> lock is not held, while, when invoked in the context where the lock
> can be held, the lock is actually held, or must be taken.

If you grab the same lock from put_rq_priv, yes, you must make it IRQ
disabling in all contexts, and use _irqsave() from put_rq_priv. If it's
just freeing resources, you could potentially wait and do that when
someone else needs them, since that part will come from proces context.
That would need two locks, though.

As I said above, I would not worry about the IRQ disabling lock.

-- 
Jens Axboe