161 lines
3.5 KiB
Go
161 lines
3.5 KiB
Go
/*
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* Copyright (C) THL A29 Limited, a Tencent company. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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*/
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package lockfree
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import (
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"runtime"
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"sync"
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"sync/atomic"
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"time"
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)
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// blockStrategy 阻塞策略
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type blockStrategy interface {
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// block 阻塞
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block(actual *uint64, expected uint64)
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// release 释放阻塞
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release()
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}
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// SchedBlockStrategy 调度等待策略
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// 调用runtime.Gosched()方法使当前 g 主动让出 cpu 资源。
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type SchedBlockStrategy struct {
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}
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func (s *SchedBlockStrategy) block(actual *uint64, expected uint64) {
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runtime.Gosched()
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}
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func (s *SchedBlockStrategy) release() {
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}
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// SleepBlockStrategy 休眠等待策略
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// 调用 Sleep 方法使当前 g 主动让出 cpu 资源。
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// sleep poll 参考值:
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// 轮询时长为 10us 时，cpu 开销约 2-3% 左右。
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// 轮询时长为 5us 时，cpu 开销约在 10% 左右。
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// 轮询时长小于 5us 时，cpu 开销接近 100% 满载。
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type SleepBlockStrategy struct {
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t time.Duration
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}
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func NewSleepBlockStrategy(wait time.Duration) *SleepBlockStrategy {
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return &SleepBlockStrategy{
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t: wait,
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}
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}
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func (s *SleepBlockStrategy) block(actual *uint64, expected uint64) {
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time.Sleep(s.t)
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}
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func (s *SleepBlockStrategy) release() {
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}
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// ProcYieldBlockStrategy CPU空指令策略
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type ProcYieldBlockStrategy struct {
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cycle uint32
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}
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func NewProcYieldBlockStrategy(cycle uint32) *ProcYieldBlockStrategy {
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return &ProcYieldBlockStrategy{
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cycle: cycle,
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}
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}
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func (s *ProcYieldBlockStrategy) block(actual *uint64, expected uint64) {
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procyield(s.cycle)
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}
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func (s *ProcYieldBlockStrategy) release() {
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}
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// OSYieldBlockStrategy 操作系统调度策略
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type OSYieldBlockStrategy struct {
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}
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func NewOSYieldWaitStrategy() *OSYieldBlockStrategy {
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return &OSYieldBlockStrategy{}
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}
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func (s *OSYieldBlockStrategy) block(actual *uint64, expected uint64) {
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osyield()
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}
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func (s *OSYieldBlockStrategy) release() {
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}
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// ChanBlockStrategy chan阻塞策略
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type ChanBlockStrategy struct {
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bc chan struct{}
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b uint32
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}
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func NewChanBlockStrategy() *ChanBlockStrategy {
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return &ChanBlockStrategy{
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bc: make(chan struct{}),
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}
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}
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func (s *ChanBlockStrategy) block(actual *uint64, expected uint64) {
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// 0：未阻塞；1：阻塞
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if atomic.CompareAndSwapUint32(&s.b, 0, 1) {
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// 设置成功的话，表示阻塞，需要进行二次判断
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if atomic.LoadUint64(actual) == expected {
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// 表示阻塞失败，因为结果是一致的，此处需要重新将状态调整回来
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if atomic.CompareAndSwapUint32(&s.b, 1, 0) {
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// 表示回调成功，直接退出即可
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return
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} else {
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// 表示有其他协程release了，则读取对应chan即可
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<-s.bc
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}
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} else {
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// 如果说结果不一致，则表示阻塞，等待被释放即可
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<-s.bc
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}
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}
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// 没有设置成功，不用关注
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}
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func (s *ChanBlockStrategy) release() {
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if atomic.CompareAndSwapUint32(&s.b, 1, 0) {
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// 表示可以释放，即chan是等待状态
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s.bc <- struct{}{}
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}
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// 无法设置则不用关心
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return
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}
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// ConditionBlockStrategy condition 阻塞策略
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type ConditionBlockStrategy struct {
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cond *sync.Cond
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}
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func NewConditionBlockStrategy() *ConditionBlockStrategy {
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return &ConditionBlockStrategy{
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cond: sync.NewCond(&sync.Mutex{}),
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}
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}
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func (s *ConditionBlockStrategy) block(actual *uint64, expected uint64) {
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s.cond.L.Lock()
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defer s.cond.L.Unlock()
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if atomic.LoadUint64(actual) == expected {
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return
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}
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s.cond.Wait()
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}
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func (s *ConditionBlockStrategy) release() {
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s.cond.L.Lock()
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defer s.cond.L.Unlock()
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s.cond.Broadcast()
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}
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