linux-kernel - Re: [PATCH v1] PM: sleep: core: Clear device async state upfront during suspend

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Message-ID: <12845851.O9o76ZdvQC@rafael.j.wysocki>
Date: Wed, 04 Feb 2026 14:54:54 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Linux PM <linux-pm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
 Saravana Kannan <saravanak@...gle.com>, Xuewen Yan <xuewen.yan@...soc.com>
Subject:
 Re: [PATCH v1] PM: sleep: core: Clear device async state upfront during
 suspend

On Wednesday, February 4, 2026 2:37:20 PM CET Ulf Hansson wrote:
> On Tue, 3 Feb 2026 at 21:37, Rafael J. Wysocki <rafael@...nel.org> wrote:
> >
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > In all of the system suspend transition phases, async state of all
> > devices needs to be cleared before starting async processing for any of
> > them because the latter may race with power.work_in_progress updates for
> > the device's parent or suppliers and if it touches bit fields from the
> > same group (for example, power.must_resume or power.wakeup_path), bit
> > field corruption is possible.
> >
> > Rearrange the code accordingly.
> >
> > Fixes: aa7a9275ab81 ("PM: sleep: Suspend async parents after suspending children")
> > Fixes: 443046d1ad66 ("PM: sleep: Make suspend of devices more asynchronous")
> > Reported-by: Xuewen Yan <xuewen.yan@...soc.com>
> > Closes: https://lore.kernel.org/linux-pm/20260203063459.12808-1-xuewen.yan@unisoc.com/
> > Cc: All applicable <stable@...r.kernel.org>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Looks good to me!
> 
> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Thanks!

In the meantime though I have decided to commit the patch below instead
because it is simpler and basically no overhead.

Please let me know if you have any concerns regarding it.

---
>From 0491f3f9f664e7e0131eb4d2a8b19c49562e5c64 Mon Sep 17 00:00:00 2001
From: Xuewen Yan <xuewen.yan@...soc.com>
Date: Wed, 4 Feb 2026 13:25:09 +0100
Subject: [PATCH] PM: sleep: core: Avoid bit field races related to work_in_progress

In all of the system suspend transition phases, the async processing of
a device may be carried out in parallel with power.work_in_progress
updates for the device's parent or suppliers and if it touches bit
fields from the same group (for example, power.must_resume or
power.wakeup_path), bit field corruption is possible.

To avoid that, turn work_in_progress in struct dev_pm_info into a proper
bool field and relocate it to save space.

Fixes: aa7a9275ab81 ("PM: sleep: Suspend async parents after suspending children")
Fixes: 443046d1ad66 ("PM: sleep: Make suspend of devices more asynchronous")
Signed-off-by: Xuewen Yan <xuewen.yan@...soc.com>
Closes: https://lore.kernel.org/linux-pm/20260203063459.12808-1-xuewen.yan@unisoc.com/
Cc: All applicable <stable@...r.kernel.org>
[ rjw: Added subject and changelog ]
Link: https://patch.msgid.link/CAB8ipk_VX2VPm706Jwa1=8NSA7_btWL2ieXmBgHr2JcULEP76g@mail.gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 include/linux/pm.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/pm.h b/include/linux/pm.h
index 98a899858ece..afcaaa37a812 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -681,10 +681,10 @@ struct dev_pm_info {
 	struct list_head	entry;
 	struct completion	completion;
 	struct wakeup_source	*wakeup;
+	bool			work_in_progress;	/* Owned by the PM core */
 	bool			wakeup_path:1;
 	bool			syscore:1;
 	bool			no_pm_callbacks:1;	/* Owned by the PM core */
-	bool			work_in_progress:1;	/* Owned by the PM core */
 	bool			smart_suspend:1;	/* Owned by the PM core */
 	bool			must_resume:1;		/* Owned by the PM core */
 	bool			may_skip_resume:1;	/* Set by subsystems */
-- 
2.51.0