4 files changed, 39 insertions, 9 deletions

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 0d2f7c8a33d6..7400900de94a 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -30,8 +30,11 @@ struct hrtimer_cpu_base;
  * Mode arguments of xxx_hrtimer functions:
  */
 enum hrtimer_mode {
-        HRTIMER_MODE_ABS,       /* Time value is absolute */
-        HRTIMER_MODE_REL,       /* Time value is relative to now */
+        HRTIMER_MODE_ABS = 0x0,         /* Time value is absolute */
+        HRTIMER_MODE_REL = 0x1,         /* Time value is relative to now */
+        HRTIMER_MODE_PINNED = 0x02,     /* Timer is bound to CPU */
+        HRTIMER_MODE_ABS_PINNED = 0x02,
+        HRTIMER_MODE_REL_PINNED = 0x03,
 };
 
 /*
diff --git a/include/linux/timer.h b/include/linux/timer.h
index 6cdb6f3331f1..ccf882eed8f8 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -163,7 +163,10 @@ extern void add_timer_on(struct timer_list *timer, int cpu);
 extern int del_timer(struct timer_list * timer);
 extern int mod_timer(struct timer_list *timer, unsigned long expires);
 extern int mod_timer_pending(struct timer_list *timer, unsigned long expires);
+extern int mod_timer_pinned(struct timer_list *timer, unsigned long expires);
 
+#define TIMER_NOT_PINNED        0
+#define TIMER_PINNED            1
 /*
  * The jiffies value which is added to now, when there is no timer
  * in the timer wheel:
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index cb8a15c19583..c71bcd549241 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -193,7 +193,8 @@ struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
  * Switch the timer base to the current CPU when possible.
  */
 static inline struct hrtimer_clock_base *
-switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base)
+switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
+                    int pinned)
 {
         struct hrtimer_clock_base *new_base;
         struct hrtimer_cpu_base *new_cpu_base;
@@ -907,9 +908,9 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
         ret = remove_hrtimer(timer, base);
 
         /* Switch the timer base, if necessary: */
-        new_base = switch_hrtimer_base(timer, base);
+        new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
 
-        if (mode == HRTIMER_MODE_REL) {
+        if (mode & HRTIMER_MODE_REL) {
                 tim = ktime_add_safe(tim, new_base->get_time());
                 /*
                  * CONFIG_TIME_LOW_RES is a temporary way for architectures
diff --git a/kernel/timer.c b/kernel/timer.c
index 5c1e84beaf4a..3424dfd11d50 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -604,7 +604,8 @@ static struct tvec_base *lock_timer_base(struct timer_list *timer,
 }
 
 static inline int
-__mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
+__mod_timer(struct timer_list *timer, unsigned long expires,
+                                                bool pending_only, int pinned)
 {
         struct tvec_base *base, *new_base;
         unsigned long flags;
@@ -668,7 +669,7 @@ out_unlock:
  */
 int mod_timer_pending(struct timer_list *timer, unsigned long expires)
 {
-        return __mod_timer(timer, expires, true);
+        return __mod_timer(timer, expires, true, TIMER_NOT_PINNED);
 }
 EXPORT_SYMBOL(mod_timer_pending);
 
@@ -702,11 +703,33 @@ int mod_timer(struct timer_list *timer, unsigned long expires)
         if (timer->expires == expires && timer_pending(timer))
                 return 1;
 
-        return __mod_timer(timer, expires, false);
+        return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);
 }
 EXPORT_SYMBOL(mod_timer);
 
 /**
+ * mod_timer_pinned - modify a timer's timeout
+ * @timer: the timer to be modified
+ * @expires: new timeout in jiffies
+ *
+ * mod_timer_pinned() is a way to update the expire field of an
+ * active timer (if the timer is inactive it will be activated)
+ * and not allow the timer to be migrated to a different CPU.
+ *
+ * mod_timer_pinned(timer, expires) is equivalent to:
+ *
+ *     del_timer(timer); timer->expires = expires; add_timer(timer);
+ */
+int mod_timer_pinned(struct timer_list *timer, unsigned long expires)
+{
+        if (timer->expires == expires && timer_pending(timer))
+                return 1;
+
+        return __mod_timer(timer, expires, false, TIMER_PINNED);
+}
+EXPORT_SYMBOL(mod_timer_pinned);
+
+/**
  * add_timer - start a timer
  * @timer: the timer to be added
  *
@@ -1356,7 +1379,7 @@ signed long __sched schedule_timeout(signed long timeout)
         expire = timeout + jiffies;
 
         setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);
-        __mod_timer(&timer, expire, false);
+        __mod_timer(&timer, expire, false, TIMER_NOT_PINNED);
         schedule();
         del_singleshot_timer_sync(&timer);