runtime: convert p.timer0When to atomic type

Updates #53821

Change-Id: I523ec61116d290ecf7b7e3eb96e468695766cb4d
Reviewed-on: https://go-review.googlesource.com/c/go/+/424396
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/runtime/proc.go

@@ -3329,7 +3329,7 @@ func dropg() {
 func checkTimers(pp *p, now int64) (rnow, pollUntil int64, ran bool) {
 	// If it's not yet time for the first timer, or the first adjusted
 	// timer, then there is nothing to do.
-	next := int64(atomic.Load64(&pp.timer0When))
+	next := int64(pp.timer0When.Load())
 	nextAdj := int64(atomic.Load64(&pp.timerModifiedEarliest))
 	if next == 0 || (nextAdj != 0 && nextAdj < next) {
 		next = nextAdj
@@ -4787,7 +4787,7 @@ func (pp *p) destroy() {
 		pp.timers = nil
 		pp.numTimers = 0
 		pp.deletedTimers = 0
-		atomic.Store64(&pp.timer0When, 0)
+		pp.timer0When.Store(0)
 		unlock(&pp.timersLock)
 		unlock(&plocal.timersLock)
 	}

src/runtime/runtime2.go

@@ -670,9 +670,8 @@ type p struct {
 	_ uint32 // Alignment for atomic fields below
 
 	// The when field of the first entry on the timer heap.
-	// This is updated using atomic functions.
 	// This is 0 if the timer heap is empty.
-	timer0When uint64
+	timer0When atomic.Uint64
 
 	// The earliest known nextwhen field of a timer with
 	// timerModifiedEarlier status. Because the timer may have been

src/runtime/time.go

@@ -301,7 +301,7 @@ func doaddtimer(pp *p, t *timer) {
 	pp.timers = append(pp.timers, t)
 	siftupTimer(pp.timers, i)
 	if t == pp.timers[0] {
-		atomic.Store64(&pp.timer0When, uint64(t.when))
+		pp.timer0When.Store(uint64(t.when))
 	}
 	atomic.Xadd(&pp.numTimers, 1)
 }
@@ -754,7 +754,7 @@ func addAdjustedTimers(pp *p, moved []*timer) {
 //
 //go:nowritebarrierrec
 func nobarrierWakeTime(pp *p) int64 {
-	next := int64(atomic.Load64(&pp.timer0When))
+	next := int64(pp.timer0When.Load())
 	nextAdj := int64(atomic.Load64(&pp.timerModifiedEarliest))
 	if next == 0 || (nextAdj != 0 && nextAdj < next) {
 		next = nextAdj
@@ -1003,9 +1003,9 @@ func verifyTimerHeap(pp *p) {
 // The caller must have locked the timers for pp.
 func updateTimer0When(pp *p) {
 	if len(pp.timers) == 0 {
-		atomic.Store64(&pp.timer0When, 0)
+		pp.timer0When.Store(0)
 	} else {
-		atomic.Store64(&pp.timer0When, uint64(pp.timers[0].when))
+		pp.timer0When.Store(uint64(pp.timers[0].when))
 	}
 }
 
@@ -1039,7 +1039,7 @@ func timeSleepUntil() int64 {
 			continue
 		}
 
-		w := int64(atomic.Load64(&pp.timer0When))
+		w := int64(pp.timer0When.Load())
 		if w != 0 && w < next {
 			next = w
 		}