3 files changed, 21 insertions, 6 deletions
diff --git a/src/runtime/mgcscavenge.go b/src/runtime/mgcscavenge.go
index 0273c8d234..0a67f74150 100644
--- a/src/runtime/mgcscavenge.go
+++ b/src/runtime/mgcscavenge.go
@@ -268,8 +268,7 @@ func scavengeSleep(ns int64) bool {
 	// because we can't close over any variables without
 	// failing escape analysis.
 	now := nanotime()
-	scavenge.timer.when = now + ns
-	startTimer(scavenge.timer)
+	resetTimer(scavenge.timer, now+ns)
 
 	// Mark ourself as asleep and go to sleep.
 	scavenge.parked = true
diff --git a/src/runtime/netpoll.go b/src/runtime/netpoll.go
index 7d18dcaeea..536dae3d4f 100644
--- a/src/runtime/netpoll.go
+++ b/src/runtime/netpoll.go
@@ -239,13 +239,12 @@ func poll_runtime_pollSetDeadline(pd *pollDesc, d int64, mode int) {
 	if pd.rt.f == nil {
 		if pd.rd > 0 {
 			pd.rt.f = rtf
-			pd.rt.when = pd.rd
 			// Copy current seq into the timer arg.
 			// Timer func will check the seq against current descriptor seq,
 			// if they differ the descriptor was reused or timers were reset.
 			pd.rt.arg = pd
 			pd.rt.seq = pd.rseq
-			addtimer(&pd.rt)
+			resettimer(&pd.rt, pd.rd)
 		}
 	} else if pd.rd != rd0 || combo != combo0 {
 		pd.rseq++ // invalidate current timers
@@ -259,10 +258,9 @@ func poll_runtime_pollSetDeadline(pd *pollDesc, d int64, mode int) {
 	if pd.wt.f == nil {
 		if pd.wd > 0 && !combo {
 			pd.wt.f = netpollWriteDeadline
-			pd.wt.when = pd.wd
 			pd.wt.arg = pd
 			pd.wt.seq = pd.wseq
-			addtimer(&pd.wt)
+			resettimer(&pd.wt, pd.wd)
 		}
 	} else if pd.wd != wd0 || combo != combo0 {
 		pd.wseq++ // invalidate current timers
diff --git a/src/runtime/time.go b/src/runtime/time.go
index d667d11244..5521b8a807 100644
--- a/src/runtime/time.go
+++ b/src/runtime/time.go
@@ -116,6 +116,15 @@ func stopTimer(t *timer) bool {
 	return deltimer(t)
 }
 
+// resetTimer resets an inactive timer, adding it to the heap.
+//go:linkname resetTimer time.resetTimer
+func resetTimer(t *timer, when int64) {
+	if raceenabled {
+		racerelease(unsafe.Pointer(t))
+	}
+	resettimer(t, when)
+}
+
 // Go runtime.
 
 // Ready the goroutine arg.
@@ -236,6 +245,15 @@ func modtimer(t *timer, when, period int64, f func(interface{}, uintptr), arg in
 	}
 }
 
+// resettimer resets an existing inactive timer to turn it into an active timer,
+// with a new time for when the timer should fire.
+// This should be called instead of addtimer if the timer value has been,
+// or may have been, used previously.
+func resettimer(t *timer, when int64) {
+	t.when = when
+	addtimer(t)
+}
+
 // Timerproc runs the time-driven events.
 // It sleeps until the next event in the tb heap.
 // If addtimer inserts a new earlier event, it wakes timerproc early.