Re: [patch 7/7] posix-timers: Prepare for PREEMPT_RT

[Peter Zijlstra]

On Wed, Jul 31, 2019 at 12:33:55AM +0200, Thomas Gleixner wrote:
> +static struct k_itimer *timer_wait_running(struct k_itimer *timer,
> +                                        unsigned long *flags)
> +{
> +     const struct k_clock *kc = READ_ONCE(timer->kclock);
> +     timer_t timer_id = READ_ONCE(timer->it_id);
> +
> +     /* Prevent kfree(timer) after dropping the lock */
> +     rcu_read_lock();
> +     unlock_timer(timer, *flags);
> +
> +     if (kc->timer_arm == common_hrtimer_arm)
> +             hrtimer_cancel_wait_running(&timer->it.real.timer);
> +     else if (kc == &alarm_clock)
> +             hrtimer_cancel_wait_running(&timer->it.alarm.alarmtimer.timer);

        else WARN();

> +     rcu_read_unlock();
> +
> +     /* Relock the timer. It might be not longer hashed. */
> +     return lock_timer(timer_id, flags);
> +}