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// 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"
"runtime/internal/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")
}
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