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>

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index f994bb8..9f850ca 100644 (file)
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1063,7 +1063,9 @@ void hrtimer_interrupt(struct clock_event_device *dev)
                basenow = ktime_add(now, base->offset);
 
                while ((node = base->first)) {
+                       enum hrtimer_restart (*fn)(struct hrtimer *);
                        struct hrtimer *timer;
+                       int restart;
 
                        timer = rb_entry(node, struct hrtimer, node);
 
@@ -1091,13 +1093,29 @@ void hrtimer_interrupt(struct clock_event_device *dev)
                                         HRTIMER_STATE_CALLBACK, 0);
                        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
                         * enqueue_hrtimer to avoid reprogramming of
                         * the event hardware. This happens at the end
                         * of this function anyway.
                         */
-                       if (timer->function(timer) != HRTIMER_NORESTART) {
+                       if (restart != HRTIMER_NORESTART) {
                                BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
                                enqueue_hrtimer(timer, base, 0);
                        }

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 5f9fb64..1a21b6f 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -514,7 +514,6 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
 {
        struct tick_sched *ts =
                container_of(timer, struct tick_sched, sched_timer);
-       struct hrtimer_cpu_base *base = timer->base->cpu_base;
        struct pt_regs *regs = get_irq_regs();
        ktime_t now = ktime_get();
        int cpu = smp_processor_id();
@@ -552,15 +551,8 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
                        touch_softlockup_watchdog();
                        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));
                profile_tick(CPU_PROFILING);
-               spin_lock(&base->lock);
        }
 
        /* Do not restart, when we are in the idle loop */