From 95621285e5f196bf106bce507c63d79b9f6b5eb5 Mon Sep 17 00:00:00 2001
From: Richard Fuchs <rfuchs@sipwise.com>
Date: Tue, 6 Feb 2024 15:07:54 -0500
Subject: [PATCH] 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  | 7 ++++++-
 include/timerthread.h | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/daemon/timerthread.c b/daemon/timerthread.c
index 2f694523e..609a8b5b0 100644
--- a/daemon/timerthread.c
+++ b/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) {
diff --git a/include/timerthread.h b/include/timerthread.h
index 0e3c38132..58b65a34b 100644
--- a/include/timerthread.h
+++ b/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 {