David Vrabel
2013-Jun-20 19:13 UTC
[PATCH 1/2] hrtimers: provide a hrtimers_late_resume() call
From: David Vrabel <david.vrabel@citrix.com>
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 <david.vrabel@citrix.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
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