Re: [PATCH v3 01/22] timer: Allow to check when the timer callback has not finished yet

From: Thomas Gleixner
Date: Wed Nov 18 2015 - 17:33:39 EST

On Wed, 18 Nov 2015, Petr Mladek wrote:
> timer_pending() checks whether the list of callbacks is empty.
> Each callback is removed from the list before it is called,
> see call_timer_fn() in __run_timers().
> Sometimes we need to make sure that the callback has finished.
> For example, if we want to free some resources that are accessed
> by the callback.
> For this purpose, this patch adds timer_active(). It checks both
> the list of callbacks and the running_timer. It takes the base_lock
> to see a consistent state.
> I plan to use it to implement delayed works in kthread worker.
> But I guess that it will have wider use. In fact, I wonder if
> timer_pending() is misused in some situations.

Well. That's nice and good. But how will that new function solve
anything? After you drop the lock the state is not longer valid.


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