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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: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2008-01-25 21:08:31 +01:00 committed by Ingo Molnar
parent 48d5e25821
commit 2d44ae4d71
2 changed files with 19 additions and 9 deletions
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20
kernel/hrtimer.c
View File

@ -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);
} }

8
kernel/time/tick-sched.c
View File

@ -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 */