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https://github.com/golang/go
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d2a9e7164e
This CL moves code from code.google.com/p/dvyukov-go-perf-dashboard, which was previously reviewed. LGTM=adg R=adg CC=golang-codereviews https://golang.org/cl/95190043
67 lines
1.2 KiB
Go
67 lines
1.2 KiB
Go
// Copyright 2013 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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// +build linux darwin freebsd
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package main
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import (
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"sync"
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"syscall"
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)
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// FileMutex is similar to sync.RWMutex, but also synchronizes across processes.
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// This implementation is based on flock syscall.
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type FileMutex struct {
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mu sync.RWMutex
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fd int
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}
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func MakeFileMutex(filename string) *FileMutex {
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if filename == "" {
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return &FileMutex{fd: -1}
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}
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fd, err := syscall.Open(filename, syscall.O_CREAT|syscall.O_RDONLY, mkdirPerm)
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if err != nil {
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panic(err)
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}
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return &FileMutex{fd: fd}
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}
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func (m *FileMutex) Lock() {
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m.mu.Lock()
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if m.fd != -1 {
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if err := syscall.Flock(m.fd, syscall.LOCK_EX); err != nil {
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panic(err)
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}
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}
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}
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func (m *FileMutex) Unlock() {
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if m.fd != -1 {
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if err := syscall.Flock(m.fd, syscall.LOCK_UN); err != nil {
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panic(err)
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}
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}
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m.mu.Unlock()
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}
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func (m *FileMutex) RLock() {
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m.mu.RLock()
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if m.fd != -1 {
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if err := syscall.Flock(m.fd, syscall.LOCK_SH); err != nil {
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panic(err)
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}
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}
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}
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func (m *FileMutex) RUnlock() {
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if m.fd != -1 {
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if err := syscall.Flock(m.fd, syscall.LOCK_UN); err != nil {
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panic(err)
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}
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}
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m.mu.RUnlock()
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}
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