device: remove starting waitgroups

In each case, the starting waitgroup did nothing but ensure
that the goroutine has launched.

Nothing downstream depends on the order in which goroutines launch,
and if the Go runtime scheduler is so broken that goroutines
don't get launched reasonably promptly, we have much deeper problems.

Given all that, simplify the code.

Passed a race-enabled stress test 25,000 times without failure.

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>

1 files changed, 1 insertions, 7 deletions

diff --git a/device/peer.go b/device/peer.go
index 78204bb..02e145c 100644
--- a/device/peer.go
+++ b/device/peer.go
@@ -66,8 +66,7 @@ type Peer struct {
 	}
 
 	routines struct {
-		sync.Mutex                // held when stopping / starting routines
-		starting   sync.WaitGroup // routines pending start
+		sync.Mutex                // held when stopping routines
 		stopping   sync.WaitGroup // routines pending stop
 		stop       chan struct{}  // size 0, stop all go routines in peer
 	}
@@ -189,10 +188,8 @@ func (peer *Peer) Start() {
 
 	// reset routine state
 
-	peer.routines.starting.Wait()
 	peer.routines.stopping.Wait()
 	peer.routines.stop = make(chan struct{})
-	peer.routines.starting.Add(PeerRoutineNumber)
 	peer.routines.stopping.Add(PeerRoutineNumber)
 
 	// prepare queues
@@ -213,7 +210,6 @@ func (peer *Peer) Start() {
 	go peer.RoutineSequentialSender()
 	go peer.RoutineSequentialReceiver()
 
-	peer.routines.starting.Wait()
 	peer.isRunning.Set(true)
 }
 
@@ -270,8 +266,6 @@ func (peer *Peer) Stop() {
 		return
 	}
 
-	peer.routines.starting.Wait()
-
 	peer.routines.Lock()
 	defer peer.routines.Unlock()