linux-kernel - Re: [PATCH 1/2] PM: runtime: Fix I/O hang due to race between resume and runtime disable

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Message-ID: <9e0301fe-9a22-4f5f-b42d-3bd3bae8d6da@acm.org>
Date: Mon, 1 Dec 2025 08:40:59 -0800
From: Bart Van Assche <bvanassche@....org>
To: YangYang <yang.yang@...o.com>, "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Jens Axboe <axboe@...nel.dk>, Pavel Machek <pavel@...nel.org>,
 Len Brown <lenb@...nel.org>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>, Danilo Krummrich <dakr@...nel.org>,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org
Subject: Re: [PATCH 1/2] PM: runtime: Fix I/O hang due to race between resume
 and runtime disable

On 11/27/25 3:29 AM, YangYang wrote:
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 66fb2071d..041d29ba4 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -323,12 +323,15 @@ int blk_queue_enter(struct request_queue *q, 
> blk_mq_req_flags_t flags)
>                   * reordered.
>                   */
>                  smp_rmb();
> -               wait_event(q->mq_freeze_wq,
> -                          (!q->mq_freeze_depth &&
> -                           blk_pm_resume_queue(pm, q)) ||
> -                          blk_queue_dying(q));
> +check:
> +               wait_event(q->mq_freeze_wq, !q->mq_freeze_depth);
> +
>                  if (blk_queue_dying(q))
>                          return -ENODEV;

This can't work. blk_mq_destroy_queue() freezes a request queue without
unfreezing it so the above code will introduce a deadlock and/or a use-
after-free if it executes concurrently with blk_mq_destroy_queue().

Bart.