Re: [patch 4/5] posix-cpu-timers: Defer timer handling to task_work

[Thomas Gleixner <tglx@linutronix.de>]

On Thu, 1 Aug 2019, Oleg Nesterov wrote:
> On 08/01, Thomas Gleixner wrote:
> >
> > +static void __run_posix_cpu_timers(struct task_struct *tsk)
> > +{
> > +	/* FIXME: Init it proper in fork or such */
> > +	init_task_work(&tsk->cpu_timer_work, posix_cpu_timers_work);
> > +	task_work_add(tsk, &tsk->cpu_timer_work, true);
> > +}
> 
> What if update_process_times/run_posix_cpu_timers is called again before
> this task does task_work_run() ?
> 
> somehow it should check that ->cpu_timer_work is not already queued...

Right.

> Or suppose that this is called when task_work_run() executes this
> cpu_timer_work. Looks like you need another flag checked by
> __run_posix_cpu_timers() and cleare in posix_cpu_timers_work() ?

That's a non issue. The only thing which can happen is that it runs through
the task_work once more to figure out there is nothing to do.

Thanks,

	tglx