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

[Rafael J. Wysocki (Intel)]

On Fri, Sep 4, 2026 at 4:17 PM Rafael J. Wysocki (Intel)
<rafael@xxxxxxxxxx> wrote:
>
> 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.

And so applied as 7.4 material, thanks!