les: fix goroutine leak in execQueue (#14480)

execQueue used an atomic counter to track whether the queue had been
closed, but the checking the counter didn't happen because the queue was
blocked on its channel.

Fix it by using a condition variable instead of sync/atomic. I tried an
implementation based on channels first, but it was hard to make it
reliable.

quit now waits for the queue loop to exit.

1 files changed, 62 insertions, 0 deletions

diff --git a/les/execqueue_test.go b/les/execqueue_test.go
new file mode 100644
index 000000000..cd45b03f2
--- /dev/null
+++ b/les/execqueue_test.go
@@ -0,0 +1,62 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package les
+
+import (
+	"testing"
+)
+
+func TestExecQueue(t *testing.T) {
+	var (
+		N        = 10000
+		q        = newExecQueue(N)
+		counter  int
+		execd    = make(chan int)
+		testexit = make(chan struct{})
+	)
+	defer q.quit()
+	defer close(testexit)
+
+	check := func(state string, wantOK bool) {
+		c := counter
+		counter++
+		qf := func() {
+			select {
+			case execd <- c:
+			case <-testexit:
+			}
+		}
+		if q.canQueue() != wantOK {
+			t.Fatalf("canQueue() == %t for %s", !wantOK, state)
+		}
+		if q.queue(qf) != wantOK {
+			t.Fatalf("canQueue() == %t for %s", !wantOK, state)
+		}
+	}
+
+	for i := 0; i < N; i++ {
+		check("queue below cap", true)
+	}
+	check("full queue", false)
+	for i := 0; i < N; i++ {
+		if c := <-execd; c != i {
+			t.Fatal("execution out of order")
+		}
+	}
+	q.quit()
+	check("closed queue", false)
+}