Question about kthread_mod_delayed_work() allowed context

[Grygorii Strashko]

Hi All,

I'd like to ask question about allowed calling context for kthread_mod_delayed_work().

The comment to kthread_mod_delayed_work() says:

 * This function is safe to call from any context including IRQ handler.
 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
 * for details.
 */

But it has del_timer_sync() inside which seems can't be called from hard_irq context:
kthread_mod_delayed_work()
  |-__kthread_cancel_work()
     |- del_timer_sync()
	|- WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE));

My use case is related to PTP processing using PTP auxiliary worker:
(commit d9535cb7b760 ("ptp: introduce ptp auxiliary worker")):
 - periodic work A is started and res-schedules itself for every dtX
 - on IRQ - the work A need to be scheduled immediately

Any advice on how to proceed?
Can kthread_queue_work() be used even if there is delayed work is
scheduled already (in general, don't care if work A will be executed one
more time after timer expiration)?

--
Best regards,
grygorii