mirror of
https://github.com/golang/go
synced 2024-09-24 01:30:13 -06:00
4b7d5f0b94
Make sure that we're moving or zeroing pointers atomically. Anything that is a multiple of pointer size and at least pointer aligned might have pointers in it. All the code looks ok except for the 1-pointer-sized moves. Fixes #13160 Update #12552 Change-Id: Ib97d9b918fa9f4cc5c56c67ed90255b7fdfb7b45 Reviewed-on: https://go-review.googlesource.com/16668 Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Run-TryBot: Keith Randall <khr@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
71 lines
1.5 KiB
Go
71 lines
1.5 KiB
Go
// run
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// Copyright 2015 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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"fmt"
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"runtime"
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)
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const N = 100000
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func main() {
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// Allocate more Ps than processors. This raises
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// the chance that we get interrupted by the OS
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// in exactly the right (wrong!) place.
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p := runtime.NumCPU()
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runtime.GOMAXPROCS(2 * p)
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// Allocate some pointers.
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ptrs := make([]*int, p)
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for i := 0; i < p; i++ {
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ptrs[i] = new(int)
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}
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// Arena where we read and write pointers like crazy.
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collider := make([]*int, p)
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done := make(chan struct{}, 2*p)
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// Start writers. They alternately write a pointer
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// and nil to a slot in the collider.
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for i := 0; i < p; i++ {
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i := i
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go func() {
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for j := 0; j < N; j++ {
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// Write a pointer using memmove.
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copy(collider[i:i+1], ptrs[i:i+1])
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// Write nil using memclr.
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// (This is a magic loop that gets lowered to memclr.)
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r := collider[i : i+1]
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for k := range r {
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r[k] = nil
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}
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}
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done <- struct{}{}
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}()
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}
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// Start readers. They read pointers from slots
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// and make sure they are valid.
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for i := 0; i < p; i++ {
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i := i
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go func() {
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for j := 0; j < N; j++ {
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var ptr [1]*int
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copy(ptr[:], collider[i:i+1])
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if ptr[0] != nil && ptr[0] != ptrs[i] {
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panic(fmt.Sprintf("bad pointer read %p!", ptr[0]))
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}
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}
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done <- struct{}{}
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}()
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}
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for i := 0; i < 2*p; i++ {
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<-done
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}
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}
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