Re: The "clockevents: Prevent timer interrupt starvation" patch causes lockups

[Eric Naim]

On 4/15/26 5:35 AM, Hanabishi wrote:
> On 14/04/2026 20:55, Thomas Gleixner wrote:
>> The one below should cover all possible holes.
>>
>> Thanks,
>>
>>          tglx
>> ---
>> diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
>> index b4d730604972..5e22697b098d 100644
>> --- a/kernel/time/clockevents.c
>> +++ b/kernel/time/clockevents.c
>> @@ -94,6 +94,9 @@ static int __clockevents_switch_state(struct
>> clock_event_device *dev,
>>       if (dev->features & CLOCK_EVT_FEAT_DUMMY)
>>           return 0;
>>   +    /* On state transitions clear the forced flag unconditionally */
>> +    dev->next_event_forced = 0;
>> +
>>       /* Transition with new state-specific callbacks */
>>       switch (state) {
>>       case CLOCK_EVT_STATE_DETACHED:
>> @@ -366,8 +369,10 @@ int clockevents_program_event(struct clock_event_device
>> *dev, ktime_t expires, b
>>       if (delta > (int64_t)dev->min_delta_ns) {
>>           delta = min(delta, (int64_t) dev->max_delta_ns);
>>           cycles = ((u64)delta * dev->mult) >> dev->shift;
>> -        if (!dev->set_next_event((unsigned long) cycles, dev))
>> +        if (!dev->set_next_event((unsigned long) cycles, dev)) {
>> +            dev->next_event_forced = 0;
>>               return 0;
>> +        }
>>       }
>>         if (dev->next_event_forced)
>> diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
>> index 7e57fa31ee26..115e0bf01276 100644
>> --- a/kernel/time/tick-broadcast.c
>> +++ b/kernel/time/tick-broadcast.c
>> @@ -108,6 +108,7 @@ static struct clock_event_device
>> *tick_get_oneshot_wakeup_device(int cpu)
>>     static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
>>   {
>> +    wd->next_event_forced = 0;
>>       /*
>>        * If we woke up early and the tick was reprogrammed in the
>>        * meantime then this may be spurious but harmless.
> 
> Ok, it does fix the problem! Thank you.
> The patch itself does not apply cleanly for 7.0 though and I had to adapt it a
> bit.
> 

Sorry for the delay folks! This patch fixes the regression and a user recently
confirmed it as well.

Feel free to add:
Tested-by: Eric Naim <dnaim@xxxxxxxxxxx>

-- 
Regards,
  Eric