// Copyright 2023 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package main import ( "fmt" "io" "log" "net" "internal/runtime/atomic" "sync" "time" _ "unsafe" // for go:linkname ) // The bug is that netpollWaiters increases monotonically. // This doesn't cause a problem until it overflows. // Use linkname to see the value. // //go:linkname netpollWaiters runtime.netpollWaiters var netpollWaiters atomic.Uint32 func init() { register("NetpollWaiters", NetpollWaiters) } func NetpollWaiters() { listener, err := net.Listen("tcp", "127.0.0.1:0") if err != nil { log.Fatal(err) } var wg sync.WaitGroup wg.Add(1) go func() { defer wg.Done() conn, err := listener.Accept() if err != nil { log.Fatal(err) } defer conn.Close() if _, err := io.Copy(io.Discard, conn); err != nil { log.Fatal(err) } }() wg.Add(1) go func() { defer wg.Done() conn, err := net.Dial("tcp", listener.Addr().String()) if err != nil { log.Fatal(err) } defer conn.Close() for i := 0; i < 10; i++ { fmt.Fprintf(conn, "%d\n", i) time.Sleep(time.Millisecond) } }() wg.Wait() if v := netpollWaiters.Load(); v != 0 { log.Fatalf("current waiters %v", v) } fmt.Println("OK") }