Revert "time: add Ticker.Reset"

This reverts CL 217362 (6e5652bebede2d53484a872f6d1dfeb498b0b50c.)

Reason for revert: Causing failures on arm64 bots. See #33184 for more info

Change-Id: I72ba40047e4138767d95aaa68842893c3508c52f
Reviewed-on: https://go-review.googlesource.com/c/go/+/220638
Reviewed-by: Ian Lance Taylor <iant@golang.org>

6 files changed, 3 insertions, 55 deletions

diff --git a/api/next.txt b/api/next.txt
index cab86a9904..ecc3c4f0b6 100644
--- a/api/next.txt
+++ b/api/next.txt
@@ -1,2 +1 @@
 pkg testing, method (*T) Deadline() (time.Time, bool)
-pkg time, method (*Ticker) Reset(Duration)
diff --git a/doc/go1.15.html b/doc/go1.15.html
index ed240d85cc..a3a089e07e 100644
--- a/doc/go1.15.html
+++ b/doc/go1.15.html
@@ -80,13 +80,3 @@ TODO
 <p>
 TODO
 </p>
-
-<dl id="time"><dt><a href="/pkg/time/">time</a></dt>
-  <dd>
-    <p><!-- golang.org/issue/33184 -->
-       The new method
-       <a href="/pkg/time#Ticker.Reset"><code>Ticker.Reset</code></a>
-       supports changing the duration of a ticker.
-    </p>
-  </dd>
-</dl><!-- time -->
diff --git a/src/runtime/time.go b/src/runtime/time.go
index 9e1129537a..af5db4cc58 100644
--- a/src/runtime/time.go
+++ b/src/runtime/time.go
@@ -233,12 +233,6 @@ func resetTimer(t *timer, when int64) {
 	resettimer(t, when)
 }
 
-// modTimer modifies an existing timer.
-//go:linkname modTimer time.modTimer
-func modTimer(t *timer, when, period int64, f func(interface{}, uintptr), arg interface{}, seq uintptr) {
-	modtimer(t, when, period, f, arg, seq)
-}
-
 // Go runtime.
 
 // Ready the goroutine arg.
@@ -408,7 +402,7 @@ func dodeltimer0(pp *p) bool {
 }
 
 // modtimer modifies an existing timer.
-// This is called by the netpoll code or time.Ticker.Reset.
+// This is called by the netpoll code.
 func modtimer(t *timer, when, period int64, f func(interface{}, uintptr), arg interface{}, seq uintptr) {
 	if when < 0 {
 		when = maxWhen
diff --git a/src/time/sleep.go b/src/time/sleep.go
index bd0ed9aaba..37de846b11 100644
--- a/src/time/sleep.go
+++ b/src/time/sleep.go
@@ -39,7 +39,6 @@ func when(d Duration) int64 {
 func startTimer(*runtimeTimer)
 func stopTimer(*runtimeTimer) bool
 func resetTimer(*runtimeTimer, int64)
-func modTimer(t *runtimeTimer, when, period int64, f func(interface{}, uintptr), arg interface{}, seq uintptr)
 
 // The Timer type represents a single event.
 // When the Timer expires, the current time will be sent on C,
diff --git a/src/time/tick.go b/src/time/tick.go
index 152d5a706b..e4cd43aa82 100644
--- a/src/time/tick.go
+++ b/src/time/tick.go
@@ -46,15 +46,6 @@ func (t *Ticker) Stop() {
 	stopTimer(&t.r)
 }
 
-// Reset stops a ticker and resets its period to the specified duration.
-// The next tick will arrive after the new period elapses.
-func (t *Ticker) Reset(d Duration) {
-	if t.r.f == nil {
-		panic("time: Reset called on uninitialized Ticker")
-	}
-	modTimer(&t.r, when(d), int64(d), t.r.f, t.r.arg, t.r.seq)
-}
-
 // Tick is a convenience wrapper for NewTicker providing access to the ticking
 // channel only. While Tick is useful for clients that have no need to shut down
 // the Ticker, be aware that without a way to shut it down the underlying
diff --git a/src/time/tick_test.go b/src/time/tick_test.go
index d05b345efb..71ea3672b8 100644
--- a/src/time/tick_test.go
+++ b/src/time/tick_test.go
@@ -36,17 +36,13 @@ func TestTicker(t *testing.T) {
 	for i := 0; i < 5; i++ {
 		ticker := NewTicker(delta)
 		t0 := Now()
-		for i := 0; i < count/2; i++ {
-			<-ticker.C
-		}
-		ticker.Reset(delta * 2)
-		for i := count / 2; i < count; i++ {
+		for i := 0; i < count; i++ {
 			<-ticker.C
 		}
 		ticker.Stop()
 		t1 := Now()
 		dt := t1.Sub(t0)
-		target := 3 * delta * Duration(count/2)
+		target := delta * Duration(count)
 		slop := target * 2 / 10
 		if dt < target-slop || dt > target+slop {
 			errs = append(errs, fmt.Sprintf("%d %s ticks took %s, expected [%s,%s]", count, delta, dt, target-slop, target+slop))
@@ -122,24 +118,3 @@ func BenchmarkTicker(b *testing.B) {
 		ticker.Stop()
 	})
 }
-
-func BenchmarkTickerReset(b *testing.B) {
-	benchmark(b, func(n int) {
-		ticker := NewTicker(Nanosecond)
-		for i := 0; i < n; i++ {
-			ticker.Reset(Nanosecond * 2)
-		}
-		ticker.Stop()
-	})
-}
-
-func BenchmarkTickerResetNaive(b *testing.B) {
-	benchmark(b, func(n int) {
-		ticker := NewTicker(Nanosecond)
-		for i := 0; i < n; i++ {
-			ticker.Stop()
-			ticker = NewTicker(Nanosecond * 2)
-		}
-		ticker.Stop()
-	})
-}