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Commit 2d44ae4d authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

hrtimer: clean up cpu->base locking tricks 



In order to more easily allow for the scheduler to use timers, clean up
the locking a bit.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 48d5e258

kernel/hrtimer.c

+19 −1
Original line number Original line Diff line number Diff line
@@ -1063,7 +1063,9 @@ void hrtimer_interrupt(struct clock_event_device *dev) 
		basenow = ktime_add(now, base->offset);

		basenow = ktime_add(now, base->offset);





		while ((node = base->first)) {

		while ((node = base->first)) {

			enum hrtimer_restart (*fn)(struct hrtimer *);

			struct hrtimer *timer;

			struct hrtimer *timer;

			int restart;





			timer = rb_entry(node, struct hrtimer, node);

			timer = rb_entry(node, struct hrtimer, node);
@@ -1091,13 +1093,29 @@ void hrtimer_interrupt(struct clock_event_device *dev) 
					 HRTIMER_STATE_CALLBACK, 0);

					 HRTIMER_STATE_CALLBACK, 0);

			timer_stats_account_hrtimer(timer);

			timer_stats_account_hrtimer(timer);





			fn = timer->function;

			if (timer->cb_mode == HRTIMER_CB_IRQSAFE_NO_SOFTIRQ) {

				/*

				 * Used for scheduler timers, avoid lock

				 * inversion with rq->lock and tasklist_lock.

				 *

				 * These timers are required to deal with

				 * enqueue expiry themselves and are not

				 * allowed to migrate.

				 */

				spin_unlock(&cpu_base->lock);

				restart = fn(timer);

				spin_lock(&cpu_base->lock);

			} else

				restart = fn(timer);



			/*

			/*

			 * Note: We clear the CALLBACK bit after

			 * Note: We clear the CALLBACK bit after

			 * enqueue_hrtimer to avoid reprogramming of

			 * enqueue_hrtimer to avoid reprogramming of

			 * the event hardware. This happens at the end

			 * the event hardware. This happens at the end

			 * of this function anyway.

			 * of this function anyway.

			 */

			 */

			if (timer->function(timer) != HRTIMER_NORESTART) {

			if (restart != HRTIMER_NORESTART) {

				BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);

				BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);

				enqueue_hrtimer(timer, base, 0);

				enqueue_hrtimer(timer, base, 0);

			}

			}

kernel/time/tick-sched.c

+0 −8
Original line number Original line Diff line number Diff line
@@ -514,7 +514,6 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) 
{

{

	struct tick_sched *ts =

	struct tick_sched *ts =

		container_of(timer, struct tick_sched, sched_timer);

		container_of(timer, struct tick_sched, sched_timer);

	struct hrtimer_cpu_base *base = timer->base->cpu_base;

	struct pt_regs *regs = get_irq_regs();

	struct pt_regs *regs = get_irq_regs();

	ktime_t now = ktime_get();

	ktime_t now = ktime_get();

	int cpu = smp_processor_id();

	int cpu = smp_processor_id();
@@ -552,15 +551,8 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) 
			touch_softlockup_watchdog();

			touch_softlockup_watchdog();

			ts->idle_jiffies++;

			ts->idle_jiffies++;

		}

		}

		/*

		 * update_process_times() might take tasklist_lock, hence

		 * drop the base lock. sched-tick hrtimers are per-CPU and

		 * never accessible by userspace APIs, so this is safe to do.

		 */

		spin_unlock(&base->lock);

		update_process_times(user_mode(regs));

		update_process_times(user_mode(regs));

		profile_tick(CPU_PROFILING);

		profile_tick(CPU_PROFILING);

		spin_lock(&base->lock);

	}

	}





	/* Do not restart, when we are in the idle loop */

	/* Do not restart, when we are in the idle loop */