2023-06-06 01:47:24

by Yu Kuai

Subject: [PATCH -next] blk-ioc: fix recursive spin_lock/unlock_irq() in ioc_clear_queue()

From: Yu Kuai <[email protected]>

Recursive spin_lock/unlock_irq() is not safe, because spin_unlock_irq()
will enable irq unconditionally:

spin_lock_irq queue_lock -> disable irq
spin_lock_irq ioc->lock
spin_unlock_irq ioc->lock -> enable irq
/*
* AA dead lock will be triggered if current context is preempted by irq,
* and irq try to hold queue_lock again.
*/
spin_unlock_irq queue_lock

Fix this problem by using spin_lock/unlock() directly for 'ioc->lock'.

Fixes: 5a0ac57c48aa ("blk-ioc: protect ioc_destroy_icq() by 'queue_lock'")
Signed-off-by: Yu Kuai <[email protected]>
---
block/blk-ioc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index d5db92e62c43..25dd4db11121 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -179,9 +179,9 @@ void ioc_clear_queue(struct request_queue *q)
* Other context won't hold ioc lock to wait for queue_lock, see
* details in ioc_release_fn().
*/
- spin_lock_irq(&icq->ioc->lock);
+ spin_lock(&icq->ioc->lock);
ioc_destroy_icq(icq);
- spin_unlock_irq(&icq->ioc->lock);
+ spin_unlock(&icq->ioc->lock);
}
spin_unlock_irq(&q->queue_lock);
}
--
2.39.2

2023-06-07 06:02:01

by Christoph Hellwig

Subject: Re: [PATCH -next] blk-ioc: fix recursive spin_lock/unlock_irq() in ioc_clear_queue()

Looks good:

Reviewed-by: Christoph Hellwig <[email protected]>

2023-06-07 14:30:48

by Jens Axboe

Subject: Re: [PATCH -next] blk-ioc: fix recursive spin_lock/unlock_irq() in ioc_clear_queue()

On Tue, 06 Jun 2023 09:14:38 +0800, Yu Kuai wrote:
> Recursive spin_lock/unlock_irq() is not safe, because spin_unlock_irq()
> will enable irq unconditionally:
>
> spin_lock_irq queue_lock -> disable irq
> spin_lock_irq ioc->lock
> spin_unlock_irq ioc->lock -> enable irq
> /*
> * AA dead lock will be triggered if current context is preempted by irq,
> * and irq try to hold queue_lock again.
> */
> spin_unlock_irq queue_lock
>
> [...]

Applied, thanks!

[1/1] blk-ioc: fix recursive spin_lock/unlock_irq() in ioc_clear_queue()
commit: a7cfa0af0c88353b4eb59db5a2a0fbe35329b3f9

Best regards,
--
Jens Axboe