3 files changed, 106 insertions, 0 deletions

diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index e83f79de863c..a93528bc16e9 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -246,6 +246,7 @@ void smp_pull_timers_interrupt(struct pt_regs *regs)
 {
         ack_APIC_irq();
         TRACE("pull timer interrupt\n");
+        hrtimer_pull();
 }
 
 struct smp_ops smp_ops = {
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index ff037f0b1b4e..b984b947f5db 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -166,6 +166,7 @@ struct hrtimer_clock_base {
  *                      event devices whether high resolution mode can be
  *                      activated.
  * @nr_events:          Total number of timer interrupt events
+ * @to_pull:            LITMUS^RT list of timers to be pulled on this cpu
  */
 struct hrtimer_cpu_base {
         spinlock_t                      lock;
@@ -175,6 +176,26 @@ struct hrtimer_cpu_base {
         int                             hres_active;
         unsigned long                   nr_events;
 #endif
+        struct list_head                to_pull;
+};
+
+#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;
 };
 
 static inline void hrtimer_set_expires(struct hrtimer *timer, ktime_t time)
@@ -343,6 +364,10 @@ __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
                          unsigned long delta_ns,
                          const enum hrtimer_mode mode, int wakeup);
 
+extern int hrtimer_start_on(int cpu, struct hrtimer_start_on_info *info,
+                        struct hrtimer *timer, ktime_t time,
+                        const enum hrtimer_mode mode);
+
 extern int hrtimer_cancel(struct hrtimer *timer);
 extern int hrtimer_try_to_cancel(struct hrtimer *timer);
 
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 3e1c36e7998f..509ecaea3016 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -46,6 +46,8 @@
 #include <linux/sched.h>
 #include <linux/timer.h>
 
+#include <litmus/litmus.h>
+
 #include <asm/uaccess.h>
 
 #include <trace/events/timer.h>
@@ -1016,6 +1018,83 @@ hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
 }
 EXPORT_SYMBOL_GPL(hrtimer_start);
 
+/**
+ *  hrtimer_pull - PULL_TIMERS_VECTOR callback on remote cpu
+ */
+void hrtimer_pull(void)
+{
+        struct hrtimer_cpu_base *base = &__get_cpu_var(hrtimer_bases);
+        struct hrtimer_start_on_info *info;
+        struct list_head *pos, *safe, list;
+
+        spin_lock(&base->lock);
+        list_replace_init(&base->to_pull, &list);
+        spin_unlock(&base->lock);
+
+        list_for_each_safe(pos, safe, &list) {
+                info = list_entry(pos, struct hrtimer_start_on_info, list);
+                TRACE("pulled timer 0x%x\n", info->timer);
+                list_del(pos);
+                hrtimer_start(info->timer, info->time, info->mode);
+        }
+}
+
+/**
+ *  hrtimer_start_on - trigger timer arming on remote cpu
+ *  @cpu:       remote cpu
+ *  @info:      save timer information for enqueuing on remote cpu
+ *  @timer:     timer to be pulled
+ *  @time:      expire time
+ *  @mode:      timer mode
+ */
+int hrtimer_start_on(int cpu, struct hrtimer_start_on_info* info,
+                struct hrtimer *timer, ktime_t time,
+                const enum hrtimer_mode mode)
+{
+        unsigned long flags;
+        struct hrtimer_cpu_base* base;
+        int in_use = 0, was_empty;
+
+        /* serialize access to info through the timer base */
+        lock_hrtimer_base(timer, &flags);
+
+        in_use = (atomic_read(&info->state) != HRTIMER_START_ON_INACTIVE);
+        if (!in_use) {
+                INIT_LIST_HEAD(&info->list);
+                info->timer = timer;
+                info->time  = time;
+                info->mode  = mode;
+                /* mark as in use */
+                atomic_set(&info->state, HRTIMER_START_ON_QUEUED);
+        }
+
+        unlock_hrtimer_base(timer, &flags);
+
+        if (!in_use) {
+                /* initiate pull  */
+                preempt_disable();
+                if (cpu == smp_processor_id()) {
+                        /* start timer locally; we may get called
+                         * with rq->lock held, do not wake up anything
+                         */
+                        __hrtimer_start_range_ns(info->timer, info->time,
+                                                 0, info->mode, 0);
+                } else {
+                        base = &per_cpu(hrtimer_bases, cpu);
+                        spin_lock_irqsave(&base->lock, flags);
+                        was_empty = list_empty(&base->to_pull);
+                        list_add(&info->list, &base->to_pull);
+                        spin_unlock_irqrestore(&base->lock, flags);
+                        if (was_empty)
+                                /* only send IPI if other no else
+                                 * has done so already
+                                 */
+                                smp_send_pull_timers(cpu);
+                }
+                preempt_enable();
+        }
+        return in_use;
+}
 
 /**
  * hrtimer_try_to_cancel - try to deactivate a timer
@@ -1597,6 +1676,7 @@ static void __cpuinit init_hrtimers_cpu(int cpu)
                 cpu_base->clock_base[i].cpu_base = cpu_base;
 
         hrtimer_init_hres(cpu_base);
+        INIT_LIST_HEAD(&cpu_base->to_pull);
 }
 
 #ifdef CONFIG_HOTPLUG_CPU