hrtimer: Store cpu-number in struct hrtimer_cpu_base

commit cddd02489f52ccf635ed65931214729a23b93cd6 upstream.

In lowres mode, hrtimers are serviced by the tick instead of a clock
event. Now it works well as long as the tick stays periodic but we
must also make sure that the hrtimers are serviced in dynticks mode.

Part of that job consist in kicking a dynticks hrtimer target in order
to make it reconsider the next tick to schedule to correctly handle the
hrtimer's expiring time. And that part isn't handled by the hrtimers
subsystem.

To prepare for fixing this, we need __hrtimer_start_range_ns() to be
able to resolve the CPU target associated to a hrtimer's object
'cpu_base' so that the kick can be centralized there.

So lets store it in the 'struct hrtimer_cpu_base' to resolve the CPU
without overhead. It is set once at CPU's online notification.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1403393357-2070-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[bwh: Backported to 3.16 as dependency of commit b9023b91dd02
 "tick: broadcast-hrtimer: Fix a race in bc_set_next":
 - Adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index e7a8d3fa91d574e322a01a4cc1fff3a30a513a15..bb4ffff31c69bdd50b8a66716df6d58d5af76ff6 100644 (file)
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -165,6 +165,7 @@ enum  hrtimer_base_type {
  * struct hrtimer_cpu_base - the per cpu clock bases
  * @lock:              lock protecting the base and associated clock bases
  *                     and timers
+ * @cpu:               cpu number
  * @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
@@ -179,6 +180,7 @@ enum  hrtimer_base_type {
  */
 struct hrtimer_cpu_base {
        raw_spinlock_t                  lock;
+       unsigned int                    cpu;
        unsigned int                    active_bases;
        unsigned int                    clock_was_set;
 #ifdef CONFIG_HIGH_RES_TIMERS

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index dbad6176fb6746581c9714bf595558692ec40235..aaf2b480d111274298438d798ceca44d88fb5a1d 100644 (file)
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1687,6 +1687,7 @@ static void init_hrtimers_cpu(int cpu)
        }
 
        cpu_base->active_bases = 0;
+       cpu_base->cpu = cpu;
        hrtimer_init_hres(cpu_base);
 }