1 files changed, 59 insertions, 0 deletions
diff --git a/src/time/internal_test.go b/src/time/internal_test.go
new file mode 100644
index 000000000..edd523bc8
--- /dev/null
+++ b/src/time/internal_test.go
@@ -0,0 +1,59 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package time
+
+func init() {
+	// force US/Pacific for time zone tests
+	ForceUSPacificForTesting()
+}
+
+var Interrupt = interrupt
+var DaysIn = daysIn
+
+func empty(arg interface{}, seq uintptr) {}
+
+// Test that a runtimeTimer with a duration so large it overflows
+// does not cause other timers to hang.
+//
+// This test has to be in internal_test.go since it fiddles with
+// unexported data structures.
+func CheckRuntimeTimerOverflow() {
+	// We manually create a runtimeTimer to bypass the overflow
+	// detection logic in NewTimer: we're testing the underlying
+	// runtime.addtimer function.
+	r := &runtimeTimer{
+		when: runtimeNano() + (1<<63 - 1),
+		f:    empty,
+		arg:  nil,
+	}
+	startTimer(r)
+
+	// Start a goroutine that should send on t.C right away.
+	t := NewTimer(1)
+
+	defer func() {
+		// Subsequent tests won't work correctly if we don't stop the
+		// overflow timer and kick the timer proc back into service.
+		//
+		// The timer proc is now sleeping and can only be awoken by
+		// adding a timer to the *beginning* of the heap. We can't
+		// wake it up by calling NewTimer since other tests may have
+		// left timers running that should have expired before ours.
+		// Instead we zero the overflow timer duration and start it
+		// once more.
+		stopTimer(r)
+		t.Stop()
+		r.when = 0
+		startTimer(r)
+	}()
+
+	// If the test fails, we will hang here until the timeout in the testing package
+	// fires, which is 10 minutes. It would be nice to catch the problem sooner,
+	// but there is no reliable way to guarantee that timerproc schedules without
+	// doing something involving timerproc itself. Previous failed attempts have
+	// tried calling runtime.Gosched and runtime.GC, but neither is reliable.
+	// So we fall back to hope: We hope we don't hang here.
+	<-t.C
+}