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Commit d8c66c5d authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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block: fix lockdep warning on io_context release put_io_context() 



11a3122f "block: strip out locking optimization in put_io_context()"
removed ioc_lock depth lockdep annoation along with locking
optimization; however, while recursing from put_io_context() is no
longer possible, ioc_release_fn() may still end up putting the last
reference of another ioc through elevator, which wlil grab ioc->lock
triggering spurious (as the ioc is always different one) A-A deadlock
warning.

As this can only happen one time from ioc_release_fn(), using non-zero
subclass from ioc_release_fn() is enough.  Use subclass 1.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent f6302f1b

block/blk-ioc.c

+14 −7
Original line number Diff line number Diff line
@@ -80,8 +80,15 @@ static void ioc_release_fn(struct work_struct *work) 
	struct io_context *ioc = container_of(work, struct io_context,

					      release_work);

	struct request_queue *last_q = NULL;

	unsigned long flags;



	spin_lock_irq(&ioc->lock);

	/*

	 * Exiting icq may call into put_io_context() through elevator

	 * which will trigger lockdep warning.  The ioc's are guaranteed to

	 * be different, use a different locking subclass here.  Use

	 * irqsave variant as there's no spin_lock_irq_nested().

	 */

	spin_lock_irqsave_nested(&ioc->lock, flags, 1);



	while (!hlist_empty(&ioc->icq_list)) {

		struct io_cq *icq = hlist_entry(ioc->icq_list.first,
@@ -103,15 +110,15 @@ static void ioc_release_fn(struct work_struct *work) 
			 */

			if (last_q) {

				spin_unlock(last_q->queue_lock);

				spin_unlock_irq(&ioc->lock);

				spin_unlock_irqrestore(&ioc->lock, flags);

				blk_put_queue(last_q);

			} else {

				spin_unlock_irq(&ioc->lock);

				spin_unlock_irqrestore(&ioc->lock, flags);

			}



			last_q = this_q;

			spin_lock_irq(this_q->queue_lock);

			spin_lock(&ioc->lock);

			spin_lock_irqsave(this_q->queue_lock, flags);

			spin_lock_nested(&ioc->lock, 1);

			continue;

		}

		ioc_exit_icq(icq);
@@ -119,10 +126,10 @@ static void ioc_release_fn(struct work_struct *work) 


	if (last_q) {

		spin_unlock(last_q->queue_lock);

		spin_unlock_irq(&ioc->lock);

		spin_unlock_irqrestore(&ioc->lock, flags);

		blk_put_queue(last_q);

	} else {

		spin_unlock_irq(&ioc->lock);

		spin_unlock_irqrestore(&ioc->lock, flags);

	}



	kmem_cache_free(iocontext_cachep, ioc);