net/http: cherry-pick http2 serveConn goroutine removal PRs

src/net/http/http2.go

@@ -87,11 +87,17 @@ func (s *Server) setHTTP2Config(conf http2ExternalServerConfig) {
 		panic("http: HTTP/2 Server already registered")
 	}
 	s.h2Config = conf
-	s.h2Config.ServeConnFunc(s.serveHTTP2Conn)
+	s.h2Config.ServeConnFunc(func(ctx context.Context, nc net.Conn, h Handler, sawClientPreface bool, upgradeReq *Request, settings []byte) {
+		s.serveHTTP2Conn(ctx, nc, h, sawClientPreface, upgradeReq, settings, nil)
+	})
 	s.configureHTTP2()
 }
 
-func (s *Server) serveHTTP2Conn(ctx context.Context, nc net.Conn, h Handler, sawClientPreface bool, upgradeReq *Request, settings []byte) {
+// serveHTTP2Conn serves nc with the HTTP/2 server. It may return before the
+// connection is done being served (an idle HTTP/2 connection doesn't hold
+// onto a goroutine); onClose, if non-nil, runs once the connection is done
+// and has been closed.
+func (s *Server) serveHTTP2Conn(ctx context.Context, nc net.Conn, h Handler, sawClientPreface bool, upgradeReq *Request, settings []byte, onClose func()) {
 	s.setupHTTP2_ServeTLS()
 	var serverUpgradeReq *http2.ServerRequest
 	if upgradeReq != nil {
@@ -106,6 +112,7 @@ func (s *Server) serveHTTP2Conn(ctx context.Context, nc net.Conn, h Handler, saw
 		SawClientPreface: sawClientPreface,
 		UpgradeRequest:   serverUpgradeReq,
 		Settings:         settings,
+		OnClose:          onClose,
 	})
 }
 

src/net/http/internal/http2/export_test.go

@@ -82,6 +82,7 @@ func (sc *serverConn) TestFlowControlConsumed() (consumed int32) {
 
 func (sc *serverConn) TestStreamExists(id uint32) bool {
 	ch := make(chan bool, 1)
+	sc.beginServeSend()
 	sc.serveMsgCh <- func(int) {
 		ch <- (sc.streams[id] != nil)
 	}
@@ -90,13 +91,22 @@ func (sc *serverConn) TestStreamExists(id uint32) bool {
 
 func (sc *serverConn) TestStreamState(id uint32) streamState {
 	ch := make(chan streamState, 1)
+	sc.beginServeSend()
 	sc.serveMsgCh <- func(int) {
 		state, _ := sc.state(id)
 		ch <- state
 	}
 	return <-ch
 }
 
+// TestServeParked reports whether the connection's serve goroutine has
+// exited because the connection is idle. See serverConn.serveLoop.
+func (sc *serverConn) TestServeParked() bool {
+	sc.parkMu.Lock()
+	defer sc.parkMu.Unlock()
+	return sc.parked
+}
+
 func (sc *serverConn) StartGracefulShutdown() { sc.startGracefulShutdown() }
 
 func (sc *serverConn) TestHPACKEncoder() *hpack.Encoder {

src/net/http/internal/http2/gotrack.go

@@ -57,6 +57,33 @@ func (g goroutineLock) checkNotOn() {
 	}
 }
 
+// A goroutineLocker is a goroutineLock whose owning goroutine can be
+// atomically replaced, for values whose owning goroutine changes over
+// their lifetime (such as the server's serve loop, which parks when
+// the connection is idle and resumes on a new goroutine).
+type goroutineLocker struct {
+	v atomic.Uint64
+}
+
+// setOwner records the current goroutine as the owner.
+func (g *goroutineLocker) setOwner() {
+	g.v.Store(uint64(newGoroutineLock()))
+}
+
+func (g *goroutineLocker) check() {
+	if !DebugGoroutines {
+		return
+	}
+	goroutineLock(g.v.Load()).check()
+}
+
+func (g *goroutineLocker) checkNotOn() {
+	if !DebugGoroutines {
+		return
+	}
+	goroutineLock(g.v.Load()).checkNotOn()
+}
+
 var goroutineSpace = []byte("goroutine ")
 
 func curGoroutineID() uint64 {