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// run
// Copyright 2022 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 (
"sync/atomic"
"unsafe"
)
var one interface{} = 1
type eface struct {
typ unsafe.Pointer
data unsafe.Pointer
}
func f(c chan struct{}) {
var x atomic.Value
go func() {
x.Swap(one) // writing using the old marker
}()
for i := 0; i < 100000; i++ {
v := x.Load() // reading using the new marker
p := (*eface)(unsafe.Pointer(&v)).typ
if uintptr(p) == ^uintptr(0) {
// We read the old marker, which the new reader
// doesn't know is a case where it should retry
// instead of returning it.
panic("bad typ field")
}
}
c <- struct{}{}
}
func main() {
c := make(chan struct{}, 10)
for i := 0; i < 10; i++ {
go f(c)
}
for i := 0; i < 10; i++ {
<-c
}
}
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