1 files changed, 67 insertions, 0 deletions
diff --git a/src/time/sleep_test.go b/src/time/sleep_test.go
index e0172bf5e0..c48e704eb7 100644
--- a/src/time/sleep_test.go
+++ b/src/time/sleep_test.go
@@ -7,6 +7,7 @@ package time_test
 import (
 	"errors"
 	"fmt"
+	"math/rand"
 	"runtime"
 	"strings"
 	"sync"
@@ -561,6 +562,72 @@ func TestTimerModifiedEarlier(t *testing.T) {
 	}
 }
 
+// Test that rapidly moving timers earlier and later doesn't cause
+// some of the sleep times to be lost.
+// Issue 47762
+func TestAdjustTimers(t *testing.T) {
+	var rnd = rand.New(rand.NewSource(Now().UnixNano()))
+
+	timers := make([]*Timer, 100)
+	states := make([]int, len(timers))
+	indices := rnd.Perm(len(timers))
+
+	for len(indices) != 0 {
+		var ii = rnd.Intn(len(indices))
+		var i = indices[ii]
+
+		var timer = timers[i]
+		var state = states[i]
+		states[i]++
+
+		switch state {
+		case 0:
+			timers[i] = NewTimer(0)
+		case 1:
+			<-timer.C // Timer is now idle.
+
+		// Reset to various long durations, which we'll cancel.
+		case 2:
+			if timer.Reset(1 * Minute) {
+				panic("shouldn't be active (1)")
+			}
+		case 4:
+			if timer.Reset(3 * Minute) {
+				panic("shouldn't be active (3)")
+			}
+		case 6:
+			if timer.Reset(2 * Minute) {
+				panic("shouldn't be active (2)")
+			}
+
+		// Stop and drain a long-duration timer.
+		case 3, 5, 7:
+			if !timer.Stop() {
+				t.Logf("timer %d state %d Stop returned false", i, state)
+				<-timer.C
+			}
+
+		// Start a short-duration timer we expect to select without blocking.
+		case 8:
+			if timer.Reset(0) {
+				t.Fatal("timer.Reset returned true")
+			}
+		case 9:
+			now := Now()
+			<-timer.C
+			dur := Since(now)
+			if dur > 750*Millisecond {
+				t.Errorf("timer %d took %v to complete", i, dur)
+			}
+
+		// Timer is done. Swap with tail and remove.
+		case 10:
+			indices[ii] = indices[len(indices)-1]
+			indices = indices[:len(indices)-1]
+		}
+	}
+}
+
 // Benchmark timer latency when the thread that creates the timer is busy with
 // other work and the timers must be serviced by other threads.
 // https://golang.org/issue/38860