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: <09ff685f-a688-4b92-a38f-c58b598b464f@acm.org>
Date: Mon, 1 Dec 2025 16:40:54 -0800
From: Bart Van Assche <bvanassche@....org>
To: "Rafael J. Wysocki" <rafael@...nel.org>, YangYang <yang.yang@...o.com>
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 12/1/25 10:47 AM, Rafael J. Wysocki wrote:
> Generally speaking, if blk_queue_enter() or __bio_queue_enter() may
> run in parallel with device_suspend_late() for q->dev, the driver of
> that device is defective, because it is responsible for preventing
> this situation from happening.  The most straightforward way to
> achieve that is to provide a .suspend() callback for q->dev that will
> runtime-resume it (and, of course, q->dev will need to be prepared for
> system suspend as appropriate after that).

Isn't the suspend / hibernation order such that no block I/O is
submitted while block devices transition to a lower power state? I'm
surprised to read that individual drivers are responsible for preventing
that blk_queue_enter() or __bio_queue_enter() run concurrently with
device_suspend_late().

Regarding the UFSHCI driver: if a UFS controller is already runtime
suspended, we want it to remain suspended during system suspend.

Thanks,

Bart.