Make OncePer.Once reentrant
The value constructor passed to OncePer.Once may call back into
Once. Replace the global mutex with a temporary channel stored
in the map using the key, and have callers for the same key
wait on the channel if they find it instead of a real value.
Test: TestOncePerReentrant
Change-Id: Ifa88a3c48981b5076b83f47fbdee5d26311725c6
diff --git a/android/onceper_test.go b/android/onceper_test.go
index d2ca9ad..f27799b 100644
--- a/android/onceper_test.go
+++ b/android/onceper_test.go
@@ -133,3 +133,14 @@
t.Errorf(`second call to Once with the NewCustomOnceKey from equal key should return "a": %q`, b)
}
}
+
+func TestOncePerReentrant(t *testing.T) {
+ once := OncePer{}
+ key1 := NewOnceKey("key")
+ key2 := NewOnceKey("key")
+
+ a := once.Once(key1, func() interface{} { return once.Once(key2, func() interface{} { return "a" }) })
+ if a != "a" {
+ t.Errorf(`reentrant Once should return "a": %q`, a)
+ }
+}