Re: [PATCH 1/2] clocksource/drivers/timer-ti-dm: Unregister CPU PM notifier outside of the timer lock

[Rafael J. Wysocki (Intel)]

On Thu, Aug 13, 2026 at 9:43 AM Bradley Morgan <include@xxxxxxxxx> wrote:
>
> omap_dm_timer_remove() calls cpu_pm_unregister_notifier() with
> dm_timer_lock held and interrupts disabled. Nothing sleeps in there
> today, but it pins the helper into a context where it can never be
> allowed to sleep, which is in the way of restoring the RCU grace
> period on the cpu_pm notifier chain.
>
> Do the list lookup under the lock and move the unregister after the
> unlock. Nothing can race it at that point: remove() owns the device,
> and once the timer is off the list nobody can reach it anymore.
>
> Signed-off-by: Bradley Morgan <include@xxxxxxxxx>
> ---
>  drivers/clocksource/timer-ti-dm.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/clocksource/timer-ti-dm.c b/drivers/clocksource/timer-ti-dm.c
> index bd06afb7d522..032e102bdd0a 100644
> --- a/drivers/clocksource/timer-ti-dm.c
> +++ b/drivers/clocksource/timer-ti-dm.c
> @@ -1530,7 +1530,7 @@ static int omap_dm_timer_probe(struct platform_device *pdev)
>   */
>  static void omap_dm_timer_remove(struct platform_device *pdev)
>  {
> -       struct dmtimer *timer;
> +       struct dmtimer *timer, *found = NULL;
>         unsigned long flags;
>         int ret = -EINVAL;
>
> @@ -1538,14 +1538,17 @@ static void omap_dm_timer_remove(struct platform_device *pdev)
>         list_for_each_entry(timer, &omap_timer_list, node)
>                 if (!strcmp(dev_name(&timer->pdev->dev),
>                             dev_name(&pdev->dev))) {
> -                       if (!(timer->capability & OMAP_TIMER_ALWON))
> -                               cpu_pm_unregister_notifier(&timer->nb);
>                         list_del(&timer->node);
> +                       found = timer;
>                         ret = 0;
>                         break;
>                 }
>         spin_unlock_irqrestore(&dm_timer_lock, flags);
>
> +       /* Unregister outside the lock: cpu_pm_unregister_notifier() may sleep. */
> +       if (found && !(found->capability & OMAP_TIMER_ALWON))
> +               cpu_pm_unregister_notifier(&found->nb);
> +
>         pm_runtime_disable(&pdev->dev);
>
>         if (ret)
> --

Nobody seems to be interested in this patch, but Sashiko only sees
pre-existing issues related to it:

https://sashiko.dev/#/patchset/20260813074343.26460-1-include%40grrlz.net

and the second patch in the series depends on it, so in the absence of
any objections or concerns, I'm going to apply them both.

Thanks!