From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: [PATCH RT 2/4] Revert "timers: do not raise softirq unconditionally" Date: Tue, 17 Mar 2015 12:30:15 -0400 Message-ID: <20150317163059.464641932@goodmis.org> References: <20150317163013.873592599@goodmis.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Cc: Thomas Gleixner , Carsten Emde , Sebastian Andrzej Siewior , John Kacur , Paul Gortmaker To: linux-kernel@vger.kernel.org, linux-rt-users Return-path: Received: from mail.kernel.org ([198.145.29.136]:37272 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932702AbbCQQbD (ORCPT ); Tue, 17 Mar 2015 12:31:03 -0400 Content-Disposition: inline; filename=0037-Revert-timers-do-not-raise-softirq-unconditionally.patch Sender: linux-rt-users-owner@vger.kernel.org List-ID: 3.12.38-rt53-rc2 stable review patch. If anyone has any objections, please let me know. ------------------ From: "Steven Rostedt (Red Hat)" This reverts commit e8886d18e87ca7a578cd85467418a0de693588ca Signed-off-by: Steven Rostedt Conflicts: kernel/timer.c --- include/linux/hrtimer.h | 3 ++- kernel/hrtimer.c | 31 ++++++++++++++++++++++++------- kernel/timer.c | 46 ++-------------------------------------------- 3 files changed, 28 insertions(+), 52 deletions(-) diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index bdbf77db0f4d..79a7a35e1a6e 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -461,8 +461,9 @@ extern int schedule_hrtimeout_range_clock(ktime_t *expires, unsigned long delta, const enum hrtimer_mode mode, int clock); extern int schedule_hrtimeout(ktime_t *expires, const enum hrtimer_mode mode); -/* Called from the periodic timer tick */ +/* Soft interrupt function to run the hrtimer queues: */ extern void hrtimer_run_queues(void); +extern void hrtimer_run_pending(void); /* Bootup initialization: */ extern void __init hrtimers_init(void); diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index c967b718ab37..ba64ab0d5792 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -1716,6 +1716,30 @@ static void run_hrtimer_softirq(struct softirq_action *h) } /* + * Called from timer softirq every jiffy, expire hrtimers: + * + * For HRT its the fall back code to run the softirq in the timer + * softirq context in case the hrtimer initialization failed or has + * not been done yet. + */ +void hrtimer_run_pending(void) +{ + if (hrtimer_hres_active()) + return; + + /* + * This _is_ ugly: We have to check in the softirq context, + * whether we can switch to highres and / or nohz mode. The + * clocksource switch happens in the timer interrupt with + * xtime_lock held. Notification from there only sets the + * check bit in the tick_oneshot code, otherwise we might + * deadlock vs. xtime_lock. + */ + if (tick_check_oneshot_change(!hrtimer_is_hres_enabled())) + hrtimer_switch_to_hres(); +} + +/* * Called from hardirq context every jiffy */ void hrtimer_run_queues(void) @@ -1728,13 +1752,6 @@ void hrtimer_run_queues(void) if (hrtimer_hres_active()) return; - /* - * Check whether we can switch to highres mode. - */ - if (tick_check_oneshot_change(!hrtimer_is_hres_enabled()) - && hrtimer_switch_to_hres()) - return; - for (index = 0; index < HRTIMER_MAX_CLOCK_BASES; index++) { base = &cpu_base->clock_base[index]; if (!timerqueue_getnext(&base->active)) diff --git a/kernel/timer.c b/kernel/timer.c index 0ee72212b99c..2d9ba1b9f698 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -1464,6 +1464,8 @@ static void run_timer_softirq(struct softirq_action *h) { struct tvec_base *base = __this_cpu_read(tvec_bases); + hrtimer_run_pending(); + #if defined(CONFIG_IRQ_WORK) && defined(CONFIG_PREEMPT_RT_FULL) irq_work_run(); #endif @@ -1477,52 +1479,8 @@ static void run_timer_softirq(struct softirq_action *h) */ void run_local_timers(void) { - struct tvec_base *base = __this_cpu_read(tvec_bases); - hrtimer_run_queues(); - /* - * We can access this lockless as we are in the timer - * interrupt. If there are no timers queued, nothing to do in - * the timer softirq. - */ -#ifdef CONFIG_PREEMPT_RT_FULL - -#ifndef CONFIG_SMP - /* - * The spin_do_trylock() later may fail as the lock may be hold before - * the interrupt arrived. The spin-lock debugging code will raise a - * warning if the try_lock fails on UP. Since this is only an - * optimization for the FULL_NO_HZ case (not to run the timer softirq on - * an nohz_full CPU) we don't really care and shedule the softirq. - */ raise_softirq(TIMER_SOFTIRQ); - return; -#endif - - /* On RT, irq work runs from softirq */ - if (irq_work_needs_cpu()) { - raise_softirq(TIMER_SOFTIRQ); - return; - } - - if (!spin_do_trylock(&base->lock)) { - raise_softirq(TIMER_SOFTIRQ); - return; - } -#endif - - if (!base->active_timers) - goto out;