Add hrtimer_start_on() support

This patch adds hrtimer_start_on(), which allows arming timers on
remote CPUs.  This is needed to avoided timer interrupts on "shielded"
CPUs and is also useful for implementing semi-partitioned schedulers.

2 files changed, 37 insertions, 0 deletions

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index d19a5c2d2270..93def50764dd 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -176,6 +176,7 @@ enum  hrtimer_base_type {
  * @nr_hangs:           Total number of hrtimer interrupt hangs
  * @max_hang_time:      Maximum time spent in hrtimer_interrupt
  * @clock_base:         array of clock bases for this cpu
+ * @to_pull:            LITMUS^RT list of timers to be pulled on this cpu
  */
 struct hrtimer_cpu_base {
         raw_spinlock_t                  lock;
@@ -191,8 +192,32 @@ struct hrtimer_cpu_base {
         ktime_t                         max_hang_time;
 #endif
         struct hrtimer_clock_base       clock_base[HRTIMER_MAX_CLOCK_BASES];
+        struct list_head                to_pull;
 };
 
+#ifdef CONFIG_ARCH_HAS_SEND_PULL_TIMERS
+
+#define HRTIMER_START_ON_INACTIVE       0
+#define HRTIMER_START_ON_QUEUED         1
+
+/*
+ * struct hrtimer_start_on_info - save timer info on remote cpu
+ * @list:       list of hrtimer_start_on_info on remote cpu (to_pull)
+ * @timer:      timer to be triggered on remote cpu
+ * @time:       time event
+ * @mode:       timer mode
+ * @state:      activity flag
+ */
+struct hrtimer_start_on_info {
+        struct list_head        list;
+        struct hrtimer          *timer;
+        ktime_t                 time;
+        enum hrtimer_mode       mode;
+        atomic_t                state;
+};
+
+#endif
+
 static inline void hrtimer_set_expires(struct hrtimer *timer, ktime_t time)
 {
         timer->node.expires = time;
@@ -366,6 +391,13 @@ __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
                          unsigned long delta_ns,
                          const enum hrtimer_mode mode, int wakeup);
 
+#ifdef CONFIG_ARCH_HAS_SEND_PULL_TIMERS
+extern void hrtimer_start_on_info_init(struct hrtimer_start_on_info *info);
+extern int hrtimer_start_on(int cpu, struct hrtimer_start_on_info *info,
+                        struct hrtimer *timer, ktime_t time,
+                        const enum hrtimer_mode mode);
+#endif
+
 extern int hrtimer_cancel(struct hrtimer *timer);
 extern int hrtimer_try_to_cancel(struct hrtimer *timer);
 
diff --git a/include/linux/smp.h b/include/linux/smp.h
index c8488763277f..4f78ea77662c 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -84,6 +84,11 @@ int smp_call_function_any(const struct cpumask *mask,
 void kick_all_cpus_sync(void);
 
 /*
+ * sends a 'pull timer' event to a remote CPU
+ */
+extern void smp_send_pull_timers(int cpu);
+
+/*
  * Generic and arch helpers
  */
 #ifdef CONFIG_USE_GENERIC_SMP_HELPERS