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authorJohn Stultz <johnstul@us.ibm.com>2012-07-10 18:43:19 -0400
committerThomas Gleixner <tglx@linutronix.de>2012-07-11 23:34:37 +0200
commitf55a6faa384304c89cfef162768e88374d3312cb (patch)
tree522b895184e6ff0ff935d5b883eb67f8ea45e993
parent055c9fa8874fa7261eec7a268366565db84af474 (diff)
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 <johnstul@us.ibm.com> Reported-by: Jan Engelhardt <jengelh@inai.de> Reviewed-by: Ingo Molnar <mingo@kernel.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Prarit Bhargava <prarit@redhat.com> 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 <tglx@linutronix.de>
-rw-r--r--include/linux/hrtimer.h9
-rw-r--r--kernel/hrtimer.c20
2 files changed, 28 insertions, 1 deletions
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();
}