From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755184AbZGNP4o (ORCPT ); Tue, 14 Jul 2009 11:56:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754800AbZGNP4n (ORCPT ); Tue, 14 Jul 2009 11:56:43 -0400 Received: from www.tglx.de ([62.245.132.106]:60345 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752599AbZGNP4m (ORCPT ); Tue, 14 Jul 2009 11:56:42 -0400 Date: Tue, 14 Jul 2009 17:56:02 +0200 (CEST) From: Thomas Gleixner To: Linus Torvalds cc: Andrew Morton , LKML Subject: [GIT pull] timer fixes for 2.6.31 Message-ID: User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Linus, Please pull the latest timers-fixes-for-linus git tree from: git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git timers-fixes-for-linus Thanks, tglx ------------------> Heiko Carstens (1): timer stats: fix quick check optimization Thomas Gleixner (2): hrtimer: migration: do not check expiry time on current CPU hrtimer: Fix migration expiry check include/linux/clockchips.h | 9 ---- include/linux/hrtimer.h | 2 +- kernel/hrtimer.c | 110 +++++++++++++++++++++++++------------------ kernel/time/clockevents.c | 11 ---- 4 files changed, 65 insertions(+), 67 deletions(-) diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h index 20a100f..3a1dbba 100644 --- a/include/linux/clockchips.h +++ b/include/linux/clockchips.h @@ -143,12 +143,3 @@ extern void clockevents_notify(unsigned long reason, void *arg); #endif #endif - -#ifdef CONFIG_GENERIC_CLOCKEVENTS -extern ktime_t clockevents_get_next_event(int cpu); -#else -static inline ktime_t clockevents_get_next_event(int cpu) -{ - return (ktime_t) { .tv64 = KTIME_MAX }; -} -#endif diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index 54648e6..4759917 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -448,7 +448,7 @@ extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf, static inline void timer_stats_account_hrtimer(struct hrtimer *timer) { - if (likely(!timer->start_pid)) + if (likely(!timer->start_site)) return; timer_stats_update_stats(timer, timer->start_pid, timer->start_site, timer->function, timer->start_comm, 0); diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 9002958..49da79a 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -191,6 +191,46 @@ struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer, } } + +/* + * Get the preferred target CPU for NOHZ + */ +static int hrtimer_get_target(int this_cpu, int pinned) +{ +#ifdef CONFIG_NO_HZ + if (!pinned && get_sysctl_timer_migration() && idle_cpu(this_cpu)) { + int preferred_cpu = get_nohz_load_balancer(); + + if (preferred_cpu >= 0) + return preferred_cpu; + } +#endif + return this_cpu; +} + +/* + * With HIGHRES=y we do not migrate the timer when it is expiring + * before the next event on the target cpu because we cannot reprogram + * the target cpu hardware and we would cause it to fire late. + * + * Called with cpu_base->lock of target cpu held. + */ +static int +hrtimer_check_target(struct hrtimer *timer, struct hrtimer_clock_base *new_base) +{ +#ifdef CONFIG_HIGH_RES_TIMERS + ktime_t expires; + + if (!new_base->cpu_base->hres_active) + return 0; + + expires = ktime_sub(hrtimer_get_expires(timer), new_base->offset); + return expires.tv64 <= new_base->cpu_base->expires_next.tv64; +#else + return 0; +#endif +} + /* * Switch the timer base to the current CPU when possible. */ @@ -200,16 +240,8 @@ switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base, { struct hrtimer_clock_base *new_base; struct hrtimer_cpu_base *new_cpu_base; - int cpu, preferred_cpu = -1; - - cpu = smp_processor_id(); -#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP) - if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu)) { - preferred_cpu = get_nohz_load_balancer(); - if (preferred_cpu >= 0) - cpu = preferred_cpu; - } -#endif + int this_cpu = smp_processor_id(); + int cpu = hrtimer_get_target(this_cpu, pinned); again: new_cpu_base = &per_cpu(hrtimer_bases, cpu); @@ -217,7 +249,7 @@ again: if (base != new_base) { /* - * We are trying to schedule the timer on the local CPU. + * We are trying to move timer to new_base. * However we can't change timer's base while it is running, * so we keep it on the same CPU. No hassle vs. reprogramming * the event source in the high resolution case. The softirq @@ -233,38 +265,12 @@ again: spin_unlock(&base->cpu_base->lock); spin_lock(&new_base->cpu_base->lock); - /* Optimized away for NOHZ=n SMP=n */ - if (cpu == preferred_cpu) { - /* Calculate clock monotonic expiry time */ -#ifdef CONFIG_HIGH_RES_TIMERS - ktime_t expires = ktime_sub(hrtimer_get_expires(timer), - new_base->offset); -#else - ktime_t expires = hrtimer_get_expires(timer); -#endif - - /* - * Get the next event on target cpu from the - * clock events layer. - * This covers the highres=off nohz=on case as well. - */ - ktime_t next = clockevents_get_next_event(cpu); - - ktime_t delta = ktime_sub(expires, next); - - /* - * We do not migrate the timer when it is expiring - * before the next event on the target cpu because - * we cannot reprogram the target cpu hardware and - * we would cause it to fire late. - */ - if (delta.tv64 < 0) { - cpu = smp_processor_id(); - spin_unlock(&new_base->cpu_base->lock); - spin_lock(&base->cpu_base->lock); - timer->base = base; - goto again; - } + if (cpu != this_cpu && hrtimer_check_target(timer, new_base)) { + cpu = this_cpu; + spin_unlock(&new_base->cpu_base->lock); + spin_lock(&base->cpu_base->lock); + timer->base = base; + goto again; } timer->base = new_base; } @@ -1276,14 +1282,22 @@ void hrtimer_interrupt(struct clock_event_device *dev) expires_next.tv64 = KTIME_MAX; + spin_lock(&cpu_base->lock); + /* + * We set expires_next to KTIME_MAX here with cpu_base->lock + * held to prevent that a timer is enqueued in our queue via + * the migration code. This does not affect enqueueing of + * timers which run their callback and need to be requeued on + * this CPU. + */ + cpu_base->expires_next.tv64 = KTIME_MAX; + base = cpu_base->clock_base; for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) { ktime_t basenow; struct rb_node *node; - spin_lock(&cpu_base->lock); - basenow = ktime_add(now, base->offset); while ((node = base->first)) { @@ -1316,11 +1330,15 @@ void hrtimer_interrupt(struct clock_event_device *dev) __run_hrtimer(timer); } - spin_unlock(&cpu_base->lock); base++; } + /* + * Store the new expiry value so the migration code can verify + * against it. + */ cpu_base->expires_next = expires_next; + spin_unlock(&cpu_base->lock); /* Reprogramming necessary ? */ if (expires_next.tv64 != KTIME_MAX) { diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c index 1ad6dd4..a6dcd67 100644 --- a/kernel/time/clockevents.c +++ b/kernel/time/clockevents.c @@ -254,15 +254,4 @@ void clockevents_notify(unsigned long reason, void *arg) spin_unlock(&clockevents_lock); } EXPORT_SYMBOL_GPL(clockevents_notify); - -ktime_t clockevents_get_next_event(int cpu) -{ - struct tick_device *td; - struct clock_event_device *dev; - - td = &per_cpu(tick_cpu_device, cpu); - dev = td->evtdev; - - return dev->next_event; -} #endif