From f55a6faa384304c89cfef162768e88374d3312cb Mon Sep 17 00:00:00 2001 From: John Stultz Date: Tue, 10 Jul 2012 18:43:19 -0400 Subject: [PATCH] hrtimer: Provide clock_was_set_delayed() clock_was_set() cannot be called from hard interrupt context because it calls on_each_cpu(). For fixing the widely reported leap seconds issue it is necessary to call it from hard interrupt context, i.e. the timer tick code, which does the timekeeping updates. Provide a new function which denotes it in the hrtimer cpu base structure of the cpu on which it is called and raise the hrtimer softirq. We then execute the clock_was_set() notificiation from softirq context in run_hrtimer_softirq(). The hrtimer softirq is rarely used, so polling the flag there is not a performance issue. [ tglx: Made it depend on CONFIG_HIGH_RES_TIMERS. We really should get rid of all this ifdeffery ASAP ] Signed-off-by: John Stultz Reported-by: Jan Engelhardt Reviewed-by: Ingo Molnar Acked-by: Peter Zijlstra Acked-by: Prarit Bhargava Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1341960205-56738-2-git-send-email-johnstul@us.ibm.com Signed-off-by: Thomas Gleixner --- include/linux/hrtimer.h | 9 ++++++++- kernel/hrtimer.c | 20 ++++++++++++++++++++ 2 files changed, 28 insertions(+), 1 deletion(-) diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index fd0dc30c9f15..c9ec9400ee5b 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -165,6 +165,7 @@ enum hrtimer_base_type { * @lock: lock protecting the base and associated clock bases * and timers * @active_bases: Bitfield to mark bases with active timers + * @clock_was_set: Indicates that clock was set from irq context. * @expires_next: absolute time of the next event which was scheduled * via clock_set_next_event() * @hres_active: State of high resolution mode @@ -177,7 +178,8 @@ enum hrtimer_base_type { */ struct hrtimer_cpu_base { raw_spinlock_t lock; - unsigned long active_bases; + unsigned int active_bases; + unsigned int clock_was_set; #ifdef CONFIG_HIGH_RES_TIMERS ktime_t expires_next; int hres_active; @@ -286,6 +288,8 @@ extern void hrtimer_peek_ahead_timers(void); # define MONOTONIC_RES_NSEC HIGH_RES_NSEC # define KTIME_MONOTONIC_RES KTIME_HIGH_RES +extern void clock_was_set_delayed(void); + #else # define MONOTONIC_RES_NSEC LOW_RES_NSEC @@ -306,6 +310,9 @@ static inline int hrtimer_is_hres_active(struct hrtimer *timer) { return 0; } + +static inline void clock_was_set_delayed(void) { } + #endif extern void clock_was_set(void); diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index ae34bf51682b..3c24fb2c25c8 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -717,6 +717,19 @@ static int hrtimer_switch_to_hres(void) return 1; } +/* + * Called from timekeeping code to reprogramm the hrtimer interrupt + * device. If called from the timer interrupt context we defer it to + * softirq context. + */ +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); +} + #else static inline int hrtimer_hres_active(void) { return 0; } @@ -1395,6 +1408,13 @@ 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(); }