syncs: add Mutex/RWMutex alias/wrappers for future mutex debugging

Updates #17852

Change-Id: I477340fb8e40686870e981ade11cd61597c34a20
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

util/eventbus/bus.go

@@ -8,8 +8,8 @@ import (
 	"log"
 	"reflect"
 	"slices"
-	"sync"
 
+	"tailscale.com/syncs"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/set"
 )
@@ -34,12 +34,12 @@ type Bus struct {
 	routeDebug hook[RoutedEvent]
 	logf       logger.Logf
 
-	topicsMu sync.Mutex
+	topicsMu syncs.Mutex
 	topics   map[reflect.Type][]*subscribeState
 
 	// Used for introspection/debugging only, not in the normal event
 	// publishing path.
-	clientsMu sync.Mutex
+	clientsMu syncs.Mutex
 	clients   set.Set[*Client]
 }
 
@@ -306,7 +306,7 @@ func (w *worker) StopAndWait() {
 type stopFlag struct {
 	// guards the lazy construction of stopped, and the value of
 	// alreadyStopped.
-	mu             sync.Mutex
+	mu             syncs.Mutex
 	stopped        chan struct{}
 	alreadyStopped bool
 }

util/eventbus/client.go

@@ -5,8 +5,8 @@ package eventbus
 
 import (
 	"reflect"
-	"sync"
 
+	"tailscale.com/syncs"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/set"
 )
@@ -22,7 +22,7 @@ type Client struct {
 	bus          *Bus
 	publishDebug hook[PublishedEvent]
 
-	mu   sync.Mutex
+	mu   syncs.Mutex
 	pub  set.Set[publisher]
 	sub  *subscribeState // Lazily created on first subscribe
 	stop stopFlag        // signaled on Close

util/eventbus/debug.go

@@ -11,10 +11,10 @@ import (
 	"runtime"
 	"slices"
 	"strings"
-	"sync"
 	"sync/atomic"
 	"time"
 
+	"tailscale.com/syncs"
 	"tailscale.com/types/logger"
 )
 
@@ -147,7 +147,7 @@ func (d *Debugger) SubscribeTypes(client *Client) []reflect.Type {
 
 // A hook collects hook functions that can be run as a group.
 type hook[T any] struct {
-	sync.Mutex
+	syncs.Mutex
 	fns []hookFn[T]
 }
 

util/eventbus/subscribe.go

@@ -8,9 +8,9 @@ import (
 	"fmt"
 	"reflect"
 	"runtime"
-	"sync"
 	"time"
 
+	"tailscale.com/syncs"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/cibuild"
 )
@@ -51,7 +51,7 @@ type subscribeState struct {
 	snapshot   chan chan []DeliveredEvent
 	debug      hook[DeliveredEvent]
 
-	outputsMu sync.Mutex
+	outputsMu syncs.Mutex
 	outputs   map[reflect.Type]subscriber
 }