mirror of
https://github.com/golang/go
synced 2024-11-18 09:14:43 -07:00
50 lines
881 B
Go
50 lines
881 B
Go
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// run
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// Copyright 2022 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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import (
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"sync/atomic"
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"unsafe"
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)
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var one interface{} = 1
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type eface struct {
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typ unsafe.Pointer
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data unsafe.Pointer
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}
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func f(c chan struct{}) {
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var x atomic.Value
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go func() {
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x.Swap(one) // writing using the old marker
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}()
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for i := 0; i < 100000; i++ {
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v := x.Load() // reading using the new marker
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p := (*eface)(unsafe.Pointer(&v)).typ
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if uintptr(p) == ^uintptr(0) {
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// We read the old marker, which the new reader
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// doesn't know is a case where it should retry
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// instead of returning it.
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panic("bad typ field")
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}
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}
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c <- struct{}{}
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}
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func main() {
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c := make(chan struct{}, 10)
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for i := 0; i < 10; i++ {
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go f(c)
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}
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for i := 0; i < 10; i++ {
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<-c
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}
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}
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