2 files changed, 82 insertions, 5 deletions

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 485a634fd6e2..28259c336679 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -112,6 +112,7 @@ enum hrtimer_cb_mode {
 struct hrtimer {
         struct rb_node                  node;
         ktime_t                         _expires;
+        ktime_t                         _softexpires;
         enum hrtimer_restart            (*function)(struct hrtimer *);
         struct hrtimer_clock_base       *base;
         unsigned long                   state;
@@ -220,20 +221,37 @@ static inline int hrtimer_is_hres_active(struct hrtimer *timer)
 static inline void hrtimer_set_expires(struct hrtimer *timer, ktime_t time)
 {
         timer->_expires = time;
+        timer->_softexpires = time;
 }
+
+static inline void hrtimer_set_expires_range(struct hrtimer *timer, ktime_t time, ktime_t delta)
+{
+        timer->_softexpires = time;
+        timer->_expires = ktime_add_safe(time, delta);
+}
+
+static inline void hrtimer_set_expires_range_ns(struct hrtimer *timer, ktime_t time, unsigned long delta)
+{
+        timer->_softexpires = time;
+        timer->_expires = ktime_add_safe(time, ns_to_ktime(delta));
+}
+
 static inline void hrtimer_set_expires_tv64(struct hrtimer *timer, s64 tv64)
 {
         timer->_expires.tv64 = tv64;
+        timer->_softexpires.tv64 = tv64;
 }
 
 static inline void hrtimer_add_expires(struct hrtimer *timer, ktime_t time)
 {
         timer->_expires = ktime_add_safe(timer->_expires, time);
+        timer->_softexpires = ktime_add_safe(timer->_softexpires, time);
 }
 
 static inline void hrtimer_add_expires_ns(struct hrtimer *timer, unsigned long ns)
 {
         timer->_expires = ktime_add_ns(timer->_expires, ns);
+        timer->_softexpires = ktime_add_ns(timer->_softexpires, ns);
 }
 
 static inline ktime_t hrtimer_get_expires(const struct hrtimer *timer)
@@ -241,10 +259,19 @@ static inline ktime_t hrtimer_get_expires(const struct hrtimer *timer)
         return timer->_expires;
 }
 
+static inline ktime_t hrtimer_get_softexpires(const struct hrtimer *timer)
+{
+        return timer->_softexpires;
+}
+
 static inline s64 hrtimer_get_expires_tv64(const struct hrtimer *timer)
 {
         return timer->_expires.tv64;
 }
+static inline s64 hrtimer_get_softexpires_tv64(const struct hrtimer *timer)
+{
+        return timer->_softexpires.tv64;
+}
 
 static inline s64 hrtimer_get_expires_ns(const struct hrtimer *timer)
 {
@@ -334,7 +361,7 @@ static inline int hrtimer_start_expires(struct hrtimer *timer,
 
 static inline int hrtimer_restart(struct hrtimer *timer)
 {
-        return hrtimer_start(timer, timer->_expires, HRTIMER_MODE_ABS);
+        return hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
 }
 
 /* Query timers: */
@@ -391,6 +418,8 @@ extern long hrtimer_nanosleep_restart(struct restart_block *restart_block);
 extern void hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
                                  struct task_struct *tsk);
 
+extern int schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
+                                                const enum hrtimer_mode mode);
 extern int schedule_hrtimeout(ktime_t *expires, const enum hrtimer_mode mode);
 
 /* Soft interrupt function to run the hrtimer queues: */
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index ae307feec74c..01483004183d 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1309,7 +1309,20 @@ void hrtimer_interrupt(struct clock_event_device *dev)
 
                         timer = rb_entry(node, struct hrtimer, node);
 
-                        if (basenow.tv64 < hrtimer_get_expires_tv64(timer)) {
+                        /*
+                         * The immediate goal for using the softexpires is
+                         * minimizing wakeups, not running timers at the
+                         * earliest interrupt after their soft expiration.
+                         * This allows us to avoid using a Priority Search
+                         * Tree, which can answer a stabbing querry for
+                         * overlapping intervals and instead use the simple
+                         * BST we already have.
+                         * We don't add extra wakeups by delaying timers that
+                         * are right-of a not yet expired timer, because that
+                         * timer will have to trigger a wakeup anyway.
+                         */
+
+                        if (basenow.tv64 < hrtimer_get_softexpires_tv64(timer)) {
                                 ktime_t expires;
 
                                 expires = ktime_sub(hrtimer_get_expires(timer),
@@ -1681,14 +1694,20 @@ void __init hrtimers_init(void)
 }
 
 /**
- * schedule_hrtimeout - sleep until timeout
+ * schedule_hrtimeout_range - sleep until timeout
  * @expires:    timeout value (ktime_t)
+ * @delta:      slack in expires timeout (ktime_t)
  * @mode:       timer mode, HRTIMER_MODE_ABS or HRTIMER_MODE_REL
  *
  * Make the current task sleep until the given expiry time has
  * elapsed. The routine will return immediately unless
  * the current task state has been set (see set_current_state()).
  *
+ * The @delta argument gives the kernel the freedom to schedule the
+ * actual wakeup to a time that is both power and performance friendly.
+ * The kernel give the normal best effort behavior for "@expires+@delta",
+ * but may decide to fire the timer earlier, but no earlier than @expires.
+ *
  * You can set the task state as follows -
  *
  * %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
@@ -1702,7 +1721,7 @@ void __init hrtimers_init(void)
  *
  * Returns 0 when the timer has expired otherwise -EINTR
  */
-int __sched schedule_hrtimeout(ktime_t *expires,
+int __sched schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
                                const enum hrtimer_mode mode)
 {
         struct hrtimer_sleeper t;
@@ -1726,7 +1745,7 @@ int __sched schedule_hrtimeout(ktime_t *expires,
         }
 
         hrtimer_init_on_stack(&t.timer, CLOCK_MONOTONIC, mode);
-        hrtimer_set_expires(&t.timer, *expires);
+        hrtimer_set_expires_range_ns(&t.timer, *expires, delta);
 
         hrtimer_init_sleeper(&t, current);
 
@@ -1744,4 +1763,33 @@ int __sched schedule_hrtimeout(ktime_t *expires,
 
         return !t.task ? 0 : -EINTR;
 }
+EXPORT_SYMBOL_GPL(schedule_hrtimeout_range);
+
+/**
+ * schedule_hrtimeout - sleep until timeout
+ * @expires:    timeout value (ktime_t)
+ * @mode:       timer mode, HRTIMER_MODE_ABS or HRTIMER_MODE_REL
+ *
+ * Make the current task sleep until the given expiry time has
+ * elapsed. The routine will return immediately unless
+ * the current task state has been set (see set_current_state()).
+ *
+ * You can set the task state as follows -
+ *
+ * %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
+ * pass before the routine returns.
+ *
+ * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
+ * delivered to the current task.
+ *
+ * The current task state is guaranteed to be TASK_RUNNING when this
+ * routine returns.
+ *
+ * Returns 0 when the timer has expired otherwise -EINTR
+ */
+int __sched schedule_hrtimeout(ktime_t *expires,
+                               const enum hrtimer_mode mode)
+{
+        return schedule_hrtimeout_range(expires, 0, mode);
+}
 EXPORT_SYMBOL_GPL(schedule_hrtimeout);