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

[Bradley Morgan]

On 4 September 2026 15:17:54 BST, "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.
>
>Thanks!
>
>
Ugh, I'll check / fix the pre existing issues now

Id like to wonder why Google didn't use their 3.8 flash, considering it's
like 10x more capable
--- Thanks!
https://lore.kernel.org/all/EE579805-42F2-4C58-B752-F28779EEB717@xxxxxxxxx/