Messages in this thread Patch in this message | | | From | John Stultz <> | Subject | [PATCH 1/3] [RFC] hrtimer: Fix clock_was_set so it is safe to call from atomic | Date | Mon, 2 Jul 2012 22:16:04 -0400 |
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NOTE:This is a prerequisite patch that's required to address the widely observed leap-second related futex/hrtimer issues.
Currently clock_was_set() is unsafe to be called from atomic context, as it calls on_each_cpu(). This causes problems when we need to adjust the time from update_wall_time().
To fix this, if clock_was_set is called we're in_atomic, we schedule a timer to fire for immedately after we're out of interrupt context to then notify the hrtimer subsystem.
CC: Prarit Bhargava <prarit@redhat.com> CC: stable@vger.kernel.org CC: Thomas Gleixner <tglx@linutronix.de> Reported-by: Jan Engelhardt <jengelh@inai.de> Signed-off-by: John Stultz <johnstul@us.ibm.com> --- kernel/hrtimer.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index ae34bf5..393fd4d 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -746,7 +746,7 @@ static inline void retrigger_next_event(void *arg) { } * resolution timer interrupts. On UP we just disable interrupts and * call the high resolution interrupt code. */ -void clock_was_set(void) +static void do_clock_was_set(unsigned long data) { #ifdef CONFIG_HIGH_RES_TIMERS /* Retrigger the CPU local events everywhere */ @@ -755,6 +755,21 @@ void clock_was_set(void) timerfd_clock_was_set(); } +static struct timer_list clock_was_set_timer; + +void clock_was_set(void) +{ + /* + * We can't call on_each_cpu() from atomic context, + * so if we're in_atomic, schedule the clock_was_set + * via a timer_list timer for right after. + */ + if (in_atomic()) + mod_timer(&clock_was_set_timer, jiffies); + else + do_clock_was_set(0); +} + /* * During resume we might have to reprogram the high resolution timer * interrupt (on the local CPU): @@ -1152,6 +1167,8 @@ static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id, base = hrtimer_clockid_to_base(clock_id); timer->base = &cpu_base->clock_base[base]; timerqueue_init(&timer->node); + init_timer(&clock_was_set_timer); + clock_was_set_timer.function = do_clock_was_set; #ifdef CONFIG_TIMER_STATS timer->start_site = NULL; -- 1.7.9.5
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