MT#55283 conditionally wake timer threads

If the timer thread is already scheduled to wake before the timer that
we want to schedule, then there is no need to wake it up for nothing.

Change-Id: I5e6174bb0347954dfc5d012befe31625fad9961a

daemon/timerthread.c

@@ -14,6 +14,7 @@ static void timerthread_thread_init(struct timerthread_thread *tt, struct timert
 	mutex_init(&tt->lock);
 	cond_init(&tt->cond);
 	tt->parent = parent;
+	ZERO(tt->next_wake);
 }
 
 void timerthread_init(struct timerthread *tt, unsigned int num, void (*func)(void *)) {
@@ -72,6 +73,7 @@ static void timerthread_run(void *p) {
 		rtpe_now = tt_obj->next_check;
 		ZERO(tt_obj->next_check);
 		tt_obj->last_run = rtpe_now;
+		ZERO(tt->next_wake);
 		mutex_unlock(&tt->lock);
 
 		// run and release
@@ -88,6 +90,7 @@ sleep:;
 		sleeptime = MIN(10000000, sleeptime); /* 100 ms at the most */
 		struct timeval tv = rtpe_now;
 		timeval_add_usec(&tv, sleeptime);
+		tt->next_wake = tv;
 		cond_timedwait(&tt->cond, &tt->lock, &tv);
 	}
 
@@ -114,7 +117,9 @@ void timerthread_obj_schedule_abs_nl(struct timerthread_obj *tt_obj, const struc
 		obj_hold(tt_obj); /* if it wasn't removed, we make a new reference */
 	tt_obj->next_check = *tv;
 	g_tree_insert(tt->tree, tt_obj, tt_obj);
-	cond_signal(&tt->cond);
+	// need to wake the thread?
+	if (tt->next_wake.tv_sec && timeval_cmp(tv, &tt->next_wake) < 0)
+		cond_signal(&tt->cond);
 }
 
 void timerthread_obj_deschedule(struct timerthread_obj *tt_obj) {

include/timerthread.h

@@ -14,6 +14,7 @@ struct timerthread_thread {
 	GTree *tree; // XXX investigate other structures
 	mutex_t lock;
 	cond_t cond;
+	struct timeval next_wake;
 };
 
 struct timerthread {