英文:
How to eliminate Data Race even with Mutex Locks around pointer variable
问题
一些初始代码在这里，
func (chm *ConcurrentHashMap) NFetchWorker() {for {key := <-NFetchWorkerPipechm.mu.RLock()data := chm.data[string(key)]chm.mu.RUnlock()if data.IsUsingNFetch {chm.mu.Lock()*(chm.data[string(key)].NFetch)--chm.mu.Unlock()}}}go NFetchWorker()
ConcurrentHashMap 结构体如下，
type ConcurrentHashMap struct {data map[string]DataBlockmu sync.RWMutex}
DataBlock 结构体如下，
type DataBlock struct {...NFetch *int32IsUsingNFetch bool...}
现在当我尝试使用 race 标志运行测试时，我得到以下警告，
Write at 0x00c00012e310 by goroutine 8:(*ConcurrentHashMap).NFetchWorker()
行号指向以下代码行，
*(chm.data[string(key)].NFetch)--
然而，如果我在 DataBlock.NFetch 中不使用指针，我就不会遇到这个问题。
但是，如果我这样做，我就失去了直接从映射中更改 NFetch 值的能力，而不需要重新分配一个新的结构体对象给映射中的哈希值，这在计算上相对昂贵。我想在不重新分配整个结构体的情况下更改 NFetch 的值，以避免数据竞争。有什么解决方案吗？
对于 Golang 来说还比较新手，我可能在这里做了一些非常愚蠢的事情，请随时指出。
更新：添加读取和写入操作函数
func (chm *ConcurrentHashMap) Get(key Key) Value {chm.mu.RLock()fetch, ok := chm.data[string(key)]chm.mu.RUnlock()if ok {if CheckValueValidity(&fetch) {NFetchWorkerPipe <- keyreturn fetch.Value} else {chm.mu.Lock()delete(chm.data, string(key))chm.mu.Unlock()}}return constants.NIL}
写入操作
func (chm *ConcurrentHashMap) Insert(key Key, value Value, options Options) {...chm.mu.Lock()chm.data[string(key)] = Block{Value: value,NFetch: nFetchOld,Expiry: time.Now().Add(delay),IsUsingNFetch: foundNFetch,IsUsingExpiry: foundTTL,mu: mutex,}chm.mu.Unlock()}
英文:
Some starter code goes here,
func (chm *ConcurrentHashMap) NFetchWorker() {for {key := <-NFetchWorkerPipechm.mu.RLock()data := chm.data[string(key)]chm.mu.RUnlock()if data.IsUsingNFetch {chm.mu.Lock()*(chm.data[string(key)].NFetch)--chm.mu.Unlock()}}}go NFetchWorker()
Struct ConcurrentHashMap looks like this,
type ConcurrentHashMap struct {data map[string]DataBlockmu sync.RWMutex}
Struct DataBlock looks like this,
type DataBlock struct {...NFetch *int32IsUsingNFetch bool...}
Now when I try to run tests with race flag enabled. I get,
Write at 0x00c00012e310 by goroutine 8:(*ConcurrentHashMap).NFetchWorker()
The line numbers point to this line.
*(chm.data[string(key)].NFetch)--
However I don't face this issue when I do not use pointer in DataBlock.NFetch.
But if I do that I lose the ability to make changes to NFetch directly from map without reassigning a whole new struct object to that hash in map, which would be relatively computationally expensive. I want to change the value of NFetch without reassigning the whole struct again for one small change while being free from DATA RACE. Any solutions??
Fairly New to Golang, I could be doing something really stupid here, feel free to point it out.
UPDATE: Adding Read and Write Op function
func (chm *ConcurrentHashMap) Get(key Key) Value {chm.mu.RLock()fetch, ok := chm.data[string(key)]chm.mu.RUnlock()if ok {if CheckValueValidity(&fetch) {NFetchWorkerPipe <- keyreturn fetch.Value} else {chm.mu.Lock()delete(chm.data, string(key))chm.mu.Unlock()}}return constants.NIL}
Write Op
func (chm *ConcurrentHashMap) Insert(key Key, value Value, options Options) {...chm.mu.Lock()chm.data[string(key)] = Block{Value: value,NFetch: nFetchOld,Expiry: time.Now().Add(delay),IsUsingNFetch: foundNFetch,IsUsingExpiry: foundTTL,mu: mutex,}chm.mu.Unlock()}
答案1
得分: 2
问题出在CheckValueValidity函数中，你在没有锁定的情况下访问了NFetch。指针在没有锁定的情况下不应该被访问。
以下是翻译好的代码：
func CheckValueValidity(value *Block) bool {if value.IsUsingExpiry && !value.Expiry.After(time.Now()) {return false}if value.IsUsingNFetch && *(value.NFetch) <= 0 {return false}return true}
这段代码应该可以工作：
func (chm *ConcurrentHashMap) Get(key Key) Value {chm.mu.RLock()fetch, ok := chm.data[string(key)]isValid := CheckValueValidity(&fetch)chm.mu.RUnlock()if ok {if isValid {NFetchWorkerPipe <- keyreturn fetch.Value} else {chm.mu.Lock()delete(chm.data, string(key))chm.mu.Unlock()}}return constants.NIL}
英文:
The problem is in the CheckValueValidity where you are accessing NFetch without locking it. Pointers should never be accessed without locking them.
func CheckValueValidity(value *Block) bool {if value.IsUsingExpiry && !value.Expiry.After(time.Now()) {return false}if value.IsUsingNFetch && *(value.NFetch) <= 0 {return false}return true}
This code should work
func (chm *ConcurrentHashMap) Get(key Key) Value {chm.mu.RLock()fetch, ok := chm.data[string(key)]isValid := CheckValueValidity(&fetch)chm.mu.RUnlock()if ok {if isValid {NFetchWorkerPipe <- keyreturn fetch.Value} else {chm.mu.Lock()delete(chm.data, string(key))chm.mu.Unlock()}}return constants.NIL}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论