2 files changed, 118 insertions, 30 deletions
diff --git a/les/execqueue.go b/les/execqueue.go
index ac779003b..614721bf0 100644
--- a/les/execqueue.go
+++ b/les/execqueue.go
@@ -16,56 +16,82 @@
 
 package les
 
-import (
-	"sync/atomic"
-)
+import "sync"
 
-// ExecQueue implements a queue that executes function calls in a single thread,
+// execQueue implements a queue that executes function calls in a single thread,
 // in the same order as they have been queued.
 type execQueue struct {
-	chn                 chan func()
-	cnt, stop, capacity int32
+	mu        sync.Mutex
+	cond      *sync.Cond
+	funcs     []func()
+	closeWait chan struct{}
 }
 
-// NewExecQueue creates a new execution queue.
-func newExecQueue(capacity int32) *execQueue {
-	q := &execQueue{
-		chn:      make(chan func(), capacity),
-		capacity: capacity,
-	}
+// newExecQueue creates a new execution queue.
+func newExecQueue(capacity int) *execQueue {
+	q := &execQueue{funcs: make([]func(), 0, capacity)}
+	q.cond = sync.NewCond(&q.mu)
 	go q.loop()
 	return q
 }
 
 func (q *execQueue) loop() {
-	for f := range q.chn {
-		atomic.AddInt32(&q.cnt, -1)
-		if atomic.LoadInt32(&q.stop) != 0 {
-			return
-		}
+	for f := q.waitNext(false); f != nil; f = q.waitNext(true) {
 		f()
 	}
+	close(q.closeWait)
 }
 
-// CanQueue returns true if more  function calls can be added to the execution queue.
+func (q *execQueue) waitNext(drop bool) (f func()) {
+	q.mu.Lock()
+	if drop {
+		// Remove the function that just executed. We do this here instead of when
+		// dequeuing so len(q.funcs) includes the function that is running.
+		q.funcs = append(q.funcs[:0], q.funcs[1:]...)
+	}
+	for !q.isClosed() {
+		if len(q.funcs) > 0 {
+			f = q.funcs[0]
+			break
+		}
+		q.cond.Wait()
+	}
+	q.mu.Unlock()
+	return f
+}
+
+func (q *execQueue) isClosed() bool {
+	return q.closeWait != nil
+}
+
+// canQueue returns true if more function calls can be added to the execution queue.
 func (q *execQueue) canQueue() bool {
-	return atomic.LoadInt32(&q.stop) == 0 && atomic.LoadInt32(&q.cnt) < q.capacity
+	q.mu.Lock()
+	ok := !q.isClosed() && len(q.funcs) < cap(q.funcs)
+	q.mu.Unlock()
+	return ok
 }
 
-// Queue adds a function call to the execution queue. Returns true if successful.
+// queue adds a function call to the execution queue. Returns true if successful.
 func (q *execQueue) queue(f func()) bool {
-	if atomic.LoadInt32(&q.stop) != 0 {
-		return false
+	q.mu.Lock()
+	ok := !q.isClosed() && len(q.funcs) < cap(q.funcs)
+	if ok {
+		q.funcs = append(q.funcs, f)
+		q.cond.Signal()
 	}
-	if atomic.AddInt32(&q.cnt, 1) > q.capacity {
-		atomic.AddInt32(&q.cnt, -1)
-		return false
-	}
-	q.chn <- f
-	return true
+	q.mu.Unlock()
+	return ok
 }
 
-// Stop stops the exec queue.
+// quit stops the exec queue.
+// quit waits for the current execution to finish before returning.
 func (q *execQueue) quit() {
-	atomic.StoreInt32(&q.stop, 1)
+	q.mu.Lock()
+	if !q.isClosed() {
+		q.closeWait = make(chan struct{})
+		q.cond.Signal()
+	}
+	q.mu.Unlock()
+	<-q.closeWait
 }
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)
+}