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>

diff --git a/device/device.go b/device/device.go
index c440679c0c84f9e41d04caa92910d1366734e311..9e2d001b9f6f490125cc0529c768081f6272e6e4 100644 (file)
--- a/device/device.go
+++ b/device/device.go
@@ -27,7 +27,6 @@ type Device struct {
        // synchronized resources (locks acquired in order)
 
        state struct {
-               starting sync.WaitGroup
                stopping sync.WaitGroup
                sync.Mutex
                changing AtomicBool
@@ -35,7 +34,6 @@ type Device struct {
        }
 
        net struct {
-               starting sync.WaitGroup
                stopping sync.WaitGroup
                sync.RWMutex
                bind          conn.Bind // bind interface
@@ -297,23 +295,18 @@ func NewDevice(tunDevice tun.Device, logger *Logger) *Device {
        // start workers
 
        cpus := runtime.NumCPU()
-       device.state.starting.Wait()
        device.state.stopping.Wait()
        for i := 0; i < cpus; i += 1 {
-               device.state.starting.Add(3)
                device.state.stopping.Add(3)
                go device.RoutineEncryption()
                go device.RoutineDecryption()
                go device.RoutineHandshake()
        }
 
-       device.state.starting.Add(2)
        device.state.stopping.Add(2)
        go device.RoutineReadFromTUN()
        go device.RoutineTUNEventReader()
 
-       device.state.starting.Wait()
-
        return device
 }
 
@@ -370,8 +363,6 @@ func (device *Device) Close() {
                return
        }
 
-       device.state.starting.Wait()
-
        device.log.Info.Println("Device closing")
        device.state.changing.Set(true)
        device.state.Lock()
@@ -527,11 +518,9 @@ func (device *Device) BindUpdate() error {
 
                // start receiving routines
 
-               device.net.starting.Add(2)
                device.net.stopping.Add(2)
                go device.RoutineReceiveIncoming(ipv4.Version, netc.bind)
                go device.RoutineReceiveIncoming(ipv6.Version, netc.bind)
-               device.net.starting.Wait()
 
                device.log.Debug.Println("UDP bind has been updated")
        }

diff --git a/device/peer.go b/device/peer.go
index 78204bbd5c3ec5f55c518066a24479dc61aa7945..02e145c0d01230e18a6e44cb596eefcbe53c7e3a 100644 (file)
--- 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()
 

diff --git a/device/receive.go b/device/receive.go
index 0a8228cf7f481e915961b95b280f0a75a6d3f4d0..839b735f60ff7f7fba6c8380a5caefe959190fef 100644 (file)
--- a/device/receive.go
+++ b/device/receive.go
@@ -111,7 +111,6 @@ func (device *Device) RoutineReceiveIncoming(IP int, bind conn.Bind) {
        }()
 
        logDebug.Println("Routine: receive incoming IPv" + strconv.Itoa(IP) + " - started")
-       device.net.starting.Done()
 
        // receive datagrams until conn is closed
 
@@ -246,7 +245,6 @@ func (device *Device) RoutineDecryption() {
                device.state.stopping.Done()
        }()
        logDebug.Println("Routine: decryption worker - started")
-       device.state.starting.Done()
 
        for {
                select {
@@ -321,7 +319,6 @@ func (device *Device) RoutineHandshake() {
        }()
 
        logDebug.Println("Routine: handshake worker - started")
-       device.state.starting.Done()
 
        for {
                if elem.buffer != nil {
@@ -521,8 +518,6 @@ func (peer *Peer) RoutineSequentialReceiver() {
 
        logDebug.Println(peer, "- Routine: sequential receiver - started")
 
-       peer.routines.starting.Done()
-
        for {
                if elem != nil {
                        if !elem.IsDropped() {

diff --git a/device/send.go b/device/send.go
index cb3e3f623ce3c5c8139a2918fcd2d7f7dcbfefd2..0801b714b3eea632456c302bcf97dd0a5aa9cb40 100644 (file)
--- a/device/send.go
+++ b/device/send.go
@@ -262,7 +262,6 @@ func (device *Device) RoutineReadFromTUN() {
        }()
 
        logDebug.Println("Routine: TUN reader - started")
-       device.state.starting.Done()
 
        var elem *QueueOutboundElement
 
@@ -372,7 +371,6 @@ func (peer *Peer) RoutineNonce() {
                peer.routines.stopping.Done()
        }()
 
-       peer.routines.starting.Done()
        logDebug.Println(peer, "- Routine: nonce worker - started")
 
 NextPacket:
@@ -507,7 +505,6 @@ func (device *Device) RoutineEncryption() {
        }()
 
        logDebug.Println("Routine: encryption worker - started")
-       device.state.starting.Done()
 
        for {
 
@@ -596,8 +593,6 @@ func (peer *Peer) RoutineSequentialSender() {
 
        logDebug.Println(peer, "- Routine: sequential sender - started")
 
-       peer.routines.starting.Done()
-
        for {
                select {
 

diff --git a/device/tun.go b/device/tun.go
index 1f88f33174caa043d31c8c6e2919d0b0b863ec0b..3816f9b2e44fbb28b5d62778c09061052ba5f483 100644 (file)
--- a/device/tun.go
+++ b/device/tun.go
@@ -20,7 +20,6 @@ func (device *Device) RoutineTUNEventReader() {
        logError := device.log.Error
 
        logDebug.Println("Routine: event worker - started")
-       device.state.starting.Done()
 
        for event := range device.tun.device.Events() {
                if event&tun.EventMTUUpdate != 0 {