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

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Message-ID: <CAPDyKFrDRRU_WxKFZ-ni9Wc8JboYB3uUHpoOM_ppzghyJ3V1ow@mail.gmail.com>
Date: Wed, 4 Feb 2026 14:37:20 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: "Rafael J. Wysocki" <rafael@...nel.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 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>

Kind regards
Uffe

> ---
>  drivers/base/power/main.c |   33 ++++++++++++++++++++++++++++++---
>  1 file changed, 30 insertions(+), 3 deletions(-)
>
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -1527,11 +1527,20 @@ static int dpm_noirq_suspend_devices(pm_
>         mutex_lock(&dpm_list_mtx);
>
>         /*
> +        * Clear the async state for all devices upfront to prevent the
> +        * power.work_in_progress updates from racing with power.must_resume
> +        * updates carried out by dpm_superior_set_must_resume(), since these
> +        * flags belong to the same group of bit fields and they should not be
> +        * updated at the same time without synchronization.
> +        */
> +       list_for_each_entry_reverse(dev, &dpm_late_early_list, power.entry)
> +               dpm_clear_async_state(dev);
> +
> +       /*
>          * Start processing "async" leaf devices upfront so they don't need to
>          * wait for the "sync" devices they don't depend on.
>          */
>         list_for_each_entry_reverse(dev, &dpm_late_early_list, power.entry) {
> -               dpm_clear_async_state(dev);
>                 if (dpm_leaf_device(dev))
>                         dpm_async_with_cleanup(dev, async_suspend_noirq);
>         }
> @@ -1732,11 +1741,20 @@ int dpm_suspend_late(pm_message_t state)
>         mutex_lock(&dpm_list_mtx);
>
>         /*
> +        * Clear the async state for all devices upfront to prevent the
> +        * power.work_in_progress updates from racing with power.wakeup_path
> +        * updates carried out by dpm_propagate_wakeup_to_parent(), since these
> +        * flags belong to the same group of bit fields and they should not be
> +        * updated at the same time without synchronization.
> +        */
> +       list_for_each_entry_reverse(dev, &dpm_suspended_list, power.entry)
> +               dpm_clear_async_state(dev);
> +
> +       /*
>          * Start processing "async" leaf devices upfront so they don't need to
>          * wait for the "sync" devices they don't depend on.
>          */
>         list_for_each_entry_reverse(dev, &dpm_suspended_list, power.entry) {
> -               dpm_clear_async_state(dev);
>                 if (dpm_leaf_device(dev))
>                         dpm_async_with_cleanup(dev, async_suspend_late);
>         }
> @@ -2023,11 +2041,20 @@ int dpm_suspend(pm_message_t state)
>         mutex_lock(&dpm_list_mtx);
>
>         /*
> +        * Clear the async state for all devices upfront to prevent the
> +        * power.work_in_progress updates from racing with power.wakeup_path
> +        * updates carried out by dpm_propagate_wakeup_to_parent(), since these
> +        * flags belong to the same group of bit fields and they should not be
> +        * updated at the same time without synchronization.
> +        */
> +       list_for_each_entry_reverse(dev, &dpm_prepared_list, power.entry)
> +               dpm_clear_async_state(dev);
> +
> +       /*
>          * Start processing "async" leaf devices upfront so they don't need to
>          * wait for the "sync" devices they don't depend on.
>          */
>         list_for_each_entry_reverse(dev, &dpm_prepared_list, power.entry) {
> -               dpm_clear_async_state(dev);
>                 if (dpm_leaf_device(dev))
>                         dpm_async_with_cleanup(dev, async_suspend);
>         }
>
>
>