From 5ec2481b7b47a4005bb446d176e5d0257400c77d Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 5 Jul 2013 12:09:18 +0200 Subject: [PATCH] hrtimers: Move SMP function call to thread context smp_call_function_* must not be called from softirq context. But clock_was_set() which calls on_each_cpu() is called from softirq context to implement a delayed clock_was_set() for the timer interrupt handler. Though that almost never gets invoked. A recent change in the resume code uses the softirq based delayed clock_was_set to support Xens resume mechanism. linux-next contains a new warning which warns if smp_call_function_* is called from softirq context which gets triggered by that Xen change. Fix this by moving the delayed clock_was_set() call to a work context. Reported-and-tested-by: Artem Savkov Reported-by: Sasha Levin Cc: David Vrabel Cc: Ingo Molnar Cc: H. Peter Anvin , Cc: Konrad Wilk Cc: John Stultz Cc: xen-devel@lists.xen.org Cc: stable@vger.kernel.org Signed-off-by: Thomas Gleixner --- kernel/hrtimer.c | 37 +++++++++++++++---------------------- 1 file changed, 15 insertions(+), 22 deletions(-) diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index e86827e94c9a..b9b9420a1297 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -721,17 +721,20 @@ static int hrtimer_switch_to_hres(void) return 1; } +static void clock_was_set_work(struct work_struct *work) +{ + clock_was_set(); +} + +static DECLARE_WORK(hrtimer_work, clock_was_set_work); + /* - * Called from timekeeping code to reprogramm the hrtimer interrupt - * device. If called from the timer interrupt context we defer it to - * softirq context. + * Called from timekeeping and resume code to reprogramm the hrtimer + * interrupt device on all cpus. */ void clock_was_set_delayed(void) { - struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases); - - cpu_base->clock_was_set = 1; - __raise_softirq_irqoff(HRTIMER_SOFTIRQ); + schedule_work(&hrtimer_work); } #else @@ -775,12 +778,7 @@ void clock_was_set(void) * During resume we might have to reprogram the high resolution timer * interrupt on all online CPUs. However, all other CPUs will be * stopped with IRQs interrupts disabled so the clock_was_set() call - * must be deferred to the softirq. - * - * The one-shot timer has already been programmed to fire immediately - * (see tick_resume_oneshot()) and this interrupt will trigger the - * softirq to run early enough to correctly reprogram the timers on - * all CPUs. + * must be deferred. */ void hrtimers_resume(void) { @@ -789,8 +787,10 @@ void hrtimers_resume(void) WARN_ONCE(!irqs_disabled(), KERN_INFO "hrtimers_resume() called with IRQs enabled!"); - cpu_base->clock_was_set = 1; - __raise_softirq_irqoff(HRTIMER_SOFTIRQ); + /* Retrigger on the local CPU */ + retrigger_next_event(NULL); + /* And schedule a retrigger for all others */ + clock_was_set_delayed(); } static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer) @@ -1441,13 +1441,6 @@ void hrtimer_peek_ahead_timers(void) static void run_hrtimer_softirq(struct softirq_action *h) { - struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases); - - if (cpu_base->clock_was_set) { - cpu_base->clock_was_set = 0; - clock_was_set(); - } - hrtimer_peek_ahead_timers(); } -- 2.39.5