> @@ -489,6 +491,12 @@ static void loop_make_request(struct request_queue *q, struct bio *old_bio)
> goto out;
> if (unlikely(rw == WRITE && (lo->lo_flags & LO_FLAGS_READ_ONLY)))
> goto out;
> + if (lo->lo_bio_count >= q->nr_congestion_on) {
> + spin_unlock_irq(&lo->lo_lock);
> + wait_event(lo->lo_req_wait, lo->lo_bio_count <
> + q->nr_congestion_off);
> + spin_lock_irq(&lo->lo_lock);
> + }
This makes me nervous. You are reading lo_bio_count outside the lock. If
you race with the prepare_to_wait() and condition check in
__wait_event(), then you will sleep forever.
md has private helpers for this, seems it would be a good idea to move
these into the regular wait includes and use them here too.
--
Jens Axboe
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