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authorPéter Szilágyi <peterke@gmail.com>2017-02-03 20:04:57 +0800
committerPéter Szilágyi <peterke@gmail.com>2017-02-03 20:04:57 +0800
commit9b5c7153c93f077862333efe0217c74ac1514d2b (patch)
tree10d9af8fdbb581513895e02a05fe593956793b35
parentd52b0c32a01b38dc008be563646af2dfbcb392d4 (diff)
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event: use sync.Once for init for faster/cleaner locking
-rw-r--r--event/feed.go16
1 files changed, 5 insertions, 11 deletions
diff --git a/event/feed.go b/event/feed.go
index 4568304df..b1b597f17 100644
--- a/event/feed.go
+++ b/event/feed.go
@@ -33,9 +33,8 @@ var errBadChannel = errors.New("event: Subscribe argument does not have sendable
//
// The zero value is ready to use.
type Feed struct {
- // sendLock has a one-element buffer and is empty when held.
- // It protects sendCases.
- sendLock chan struct{}
+ once sync.Once // ensures that init only runs once
+ sendLock chan struct{} // sendLock has a one-element buffer and is empty when held.It protects sendCases.
removeSub chan interface{} // interrupts Send
sendCases caseList // the active set of select cases used by Send
@@ -60,9 +59,6 @@ func (e feedTypeError) Error() string {
}
func (f *Feed) init() {
- if f.sendLock != nil {
- return
- }
f.removeSub = make(chan interface{})
f.sendLock = make(chan struct{}, 1)
f.sendLock <- struct{}{}
@@ -75,6 +71,8 @@ func (f *Feed) init() {
// The channel should have ample buffer space to avoid blocking other subscribers.
// Slow subscribers are not dropped.
func (f *Feed) Subscribe(channel interface{}) Subscription {
+ f.once.Do(f.init)
+
chanval := reflect.ValueOf(channel)
chantyp := chanval.Type()
if chantyp.Kind() != reflect.Chan || chantyp.ChanDir()&reflect.SendDir == 0 {
@@ -84,7 +82,6 @@ func (f *Feed) Subscribe(channel interface{}) Subscription {
f.mu.Lock()
defer f.mu.Unlock()
- f.init()
if !f.typecheck(chantyp.Elem()) {
panic(feedTypeError{op: "Subscribe", got: chantyp, want: reflect.ChanOf(reflect.SendDir, f.etype)})
}
@@ -130,10 +127,7 @@ func (f *Feed) remove(sub *feedSub) {
// Send delivers to all subscribed channels simultaneously.
// It returns the number of subscribers that the value was sent to.
func (f *Feed) Send(value interface{}) (nsent int) {
- f.mu.Lock()
- f.init()
- f.mu.Unlock()
-
+ f.once.Do(f.init)
<-f.sendLock
// Add new cases from the inbox after taking the send lock.