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Commit 7300711e authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

clockevents: broadcast fixup possible waiters 



Until the C1E patches arrived there where no users of periodic broadcast
before switching to oneshot mode. Now we need to trigger a possible
waiter for a periodic broadcast when switching to oneshot mode.
Otherwise we can starve them for ever.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 7cfb0435

kernel/time/tick-broadcast.c

+36 −1
Original line number Diff line number Diff line
@@ -491,6 +491,18 @@ static void tick_broadcast_clear_oneshot(int cpu) 
	cpu_clear(cpu, tick_broadcast_oneshot_mask);

}



static void tick_broadcast_init_next_event(cpumask_t *mask, ktime_t expires)

{

	struct tick_device *td;

	int cpu;



	for_each_cpu_mask_nr(cpu, *mask) {

		td = &per_cpu(tick_cpu_device, cpu);

		if (td->evtdev)

			td->evtdev->next_event = expires;

	}

}



/**

 * tick_broadcast_setup_oneshot - setup the broadcast device

 */
@@ -498,8 +510,31 @@ void tick_broadcast_setup_oneshot(struct clock_event_device *bc) 
{

	/* Set it up only once ! */

	if (bc->event_handler != tick_handle_oneshot_broadcast) {

		int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;

		int cpu = smp_processor_id();

		cpumask_t mask;



		bc->event_handler = tick_handle_oneshot_broadcast;

		clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);



		/* Take the do_timer update */

		tick_do_timer_cpu = cpu;



		/*

		 * We must be careful here. There might be other CPUs

		 * waiting for periodic broadcast. We need to set the

		 * oneshot_mask bits for those and program the

		 * broadcast device to fire.

		 */

		mask = tick_broadcast_mask;

		cpu_clear(cpu, mask);

		cpus_or(tick_broadcast_oneshot_mask,

			tick_broadcast_oneshot_mask, mask);



		if (was_periodic && !cpus_empty(mask)) {

			tick_broadcast_init_next_event(&mask, tick_next_period);

			tick_broadcast_set_event(tick_next_period, 1);

		} else

			bc->next_event.tv64 = KTIME_MAX;

	}

}