time: prevent a panic from leaving the timer mutex held
When deleting a timer, a panic due to nil deref
would leave a lock held, possibly leading to a deadlock
in a defer. Instead return false on a nil timer.
Fixes #5745.
R=golang-dev, daniel.morsing, dvyukov, rsc, iant
CC=golang-dev
https://golang.org/cl/10373047
diff --git a/src/pkg/time/sleep_test.go b/src/pkg/time/sleep_test.go
index 1322f06..603adc9 100644
--- a/src/pkg/time/sleep_test.go
+++ b/src/pkg/time/sleep_test.go
@@ -314,3 +314,23 @@
t.Fatalf("negative timeout didn't fire")
}
}
+
+// Test that a panic while deleting a timer does not leave
+// the timers mutex held, deadlocking a ticker.Stop in a defer.
+func TestIssue5745(t *testing.T) {
+ ticker := NewTicker(Hour)
+ defer func() {
+ // would deadlock here before the fix due to
+ // lock taken before the segfault.
+ ticker.Stop()
+
+ if r := recover(); r == nil {
+ t.Error("Expected panic, but none happened.")
+ }
+ }()
+
+ // cause a panic due to a segfault
+ var timer *Timer
+ timer.Stop()
+ t.Error("Should be unreachable.")
+}
