From: David Vrabel <[email protected]> Xen suspends (and resumes) without disabling non-boot CPUs as doing so adds considerable delay to live migrations. A 4 VCPU guest had more than 200 ms of additional downtime if disable_nonboot_cpus() was called prior to suspending.
As a consequence, only high resolution timers on the current CPU are retriggered when resuming. The Xen resume path worked around this with a call to clock_was_set() to retrigger timers on all the CPUs. A subsequent change will make clock_was_set() internal to hrtimers so add an new call (hrtimers_late_resume()) to do the same job. Signed-off-by: David Vrabel <[email protected]> Cc: Thomas Gleixner <[email protected]> --- drivers/xen/manage.c | 8 ++++++-- include/linux/hrtimer.h | 1 + kernel/hrtimer.c | 9 +++++++++ 3 files changed, 16 insertions(+), 2 deletions(-) diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c index 412b96c..75bc2d5 100644 --- a/drivers/xen/manage.c +++ b/drivers/xen/manage.c @@ -166,8 +166,12 @@ out_resume: dpm_resume_end(si.cancelled ? PMSG_THAW : PMSG_RESTORE); - /* Make sure timer events get retriggered on all CPUs */ - clock_was_set(); + /* + * syscore_resume() ends up calling hrtimer_resume() but this + * only retriggers timer events on the current CPU. We need + * to retrigger the events on all the other CPUS. + */ + hrtimers_late_resume(); out_thaw: #ifdef CONFIG_PREEMPT diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index d19a5c2..13df0fa 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -323,6 +323,7 @@ extern void timerfd_clock_was_set(void); static inline void timerfd_clock_was_set(void) { } #endif extern void hrtimers_resume(void); +extern void hrtimers_late_resume(void); extern ktime_t ktime_get(void); extern ktime_t ktime_get_real(void); diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index fd4b13b..34384b4 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -784,6 +784,15 @@ void hrtimers_resume(void) timerfd_clock_was_set(); } +/* + * If non-boot CPUs were online during resume, we need to retrigger + * the events for all the non-boot CPUs. + */ +void hrtimers_late_resume(void) +{ + clock_was_set(); +} + static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer) { #ifdef CONFIG_TIMER_STATS -- 1.7.2.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
