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

Updates #17852

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

wgengine/magicsock/blockforever_conn.go

@@ -10,11 +10,13 @@ import (
 	"sync"
 	"syscall"
 	"time"
+
+	"tailscale.com/syncs"
 )
 
 // blockForeverConn is a net.PacketConn whose reads block until it is closed.
 type blockForeverConn struct {
-	mu     sync.Mutex
+	mu     syncs.Mutex
 	cond   *sync.Cond
 	closed bool
 }

wgengine/magicsock/endpoint.go

@@ -17,7 +17,6 @@ import (
 	"reflect"
 	"runtime"
 	"slices"
-	"sync"
 	"sync/atomic"
 	"time"
 
@@ -28,6 +27,7 @@ import (
 	"tailscale.com/net/packet"
 	"tailscale.com/net/stun"
 	"tailscale.com/net/tstun"
+	"tailscale.com/syncs"
 	"tailscale.com/tailcfg"
 	"tailscale.com/tstime/mono"
 	"tailscale.com/types/key"
@@ -73,7 +73,7 @@ type endpoint struct {
 	disco atomic.Pointer[endpointDisco] // if the peer supports disco, the key and short string
 
 	// mu protects all following fields.
-	mu sync.Mutex // Lock ordering: Conn.mu, then endpoint.mu
+	mu syncs.Mutex // Lock ordering: Conn.mu, then endpoint.mu
 
 	heartBeatTimer            *time.Timer    // nil when idle
 	lastSendExt               mono.Time      // last time there were outgoing packets sent to this peer from an external trigger (e.g. wireguard-go or disco pingCLI)

wgengine/magicsock/endpoint_tracker.go

@@ -6,9 +6,9 @@ package magicsock
 import (
 	"net/netip"
 	"slices"
-	"sync"
 	"time"
 
+	"tailscale.com/syncs"
 	"tailscale.com/tailcfg"
 	"tailscale.com/tempfork/heap"
 	"tailscale.com/util/mak"
@@ -107,7 +107,7 @@ func (eh endpointHeap) Min() *endpointTrackerEntry {
 //
 // See tailscale/tailscale#7877 for more information.
 type endpointTracker struct {
-	mu        sync.Mutex
+	mu        syncs.Mutex
 	endpoints map[netip.Addr]*endpointHeap
 }
 

wgengine/magicsock/magicsock.go

@@ -286,7 +286,7 @@ type Conn struct {
 	// mu guards all following fields; see userspaceEngine lock
 	// ordering rules against the engine. For derphttp, mu must
 	// be held before derphttp.Client.mu.
-	mu     sync.Mutex
+	mu     syncs.Mutex
 	muCond *sync.Cond
 
 	onlyTCP443 atomic.Bool

wgengine/magicsock/rebinding_conn.go

@@ -8,7 +8,6 @@ import (
 	"fmt"
 	"net"
 	"net/netip"
-	"sync"
 	"sync/atomic"
 	"syscall"
 
@@ -16,6 +15,7 @@ import (
 	"tailscale.com/net/batching"
 	"tailscale.com/net/netaddr"
 	"tailscale.com/net/packet"
+	"tailscale.com/syncs"
 	"tailscale.com/types/nettype"
 )
 
@@ -31,7 +31,7 @@ type RebindingUDPConn struct {
 	// Neither is expected to be nil, sockets are bound on creation.
 	pconnAtomic atomic.Pointer[nettype.PacketConn]
 
-	mu    sync.Mutex // held while changing pconn (and pconnAtomic)
+	mu    syncs.Mutex // held while changing pconn (and pconnAtomic)
 	pconn nettype.PacketConn
 	port  uint16
 }

wgengine/magicsock/relaymanager.go

@@ -15,6 +15,7 @@ import (
 	"tailscale.com/net/packet"
 	"tailscale.com/net/stun"
 	udprelay "tailscale.com/net/udprelay/endpoint"
+	"tailscale.com/syncs"
 	"tailscale.com/tailcfg"
 	"tailscale.com/tstime"
 	"tailscale.com/types/key"
@@ -58,7 +59,7 @@ type relayManager struct {
 	getServersCh        chan chan set.Set[candidatePeerRelay]
 	derpHomeChangeCh    chan derpHomeChangeEvent
 
-	discoInfoMu            sync.Mutex // guards the following field
+	discoInfoMu            syncs.Mutex // guards the following field
 	discoInfoByServerDisco map[key.DiscoPublic]*relayHandshakeDiscoInfo
 
 	// runLoopStoppedCh is written to by runLoop() upon return, enabling event

wgengine/netlog/netlog.go

@@ -15,7 +15,6 @@ import (
 	"log"
 	"net/http"
 	"net/netip"
-	"sync"
 	"time"
 
 	"tailscale.com/health"
@@ -24,6 +23,7 @@ import (
 	"tailscale.com/net/netmon"
 	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tsaddr"
+	"tailscale.com/syncs"
 	"tailscale.com/types/ipproto"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/logid"
@@ -57,7 +57,7 @@ func (noopDevice) SetConnectionCounter(netlogfunc.ConnectionCounter) {}
 // unless the Tailnet administrator opts-into explicit logging.
 // The zero value is ready for use.
 type Logger struct {
-	mu   sync.Mutex // protects all fields below
+	mu   syncs.Mutex // protects all fields below
 	logf logger.Logf
 
 	// shutdownLocked shuts down the logger.