go runtime_error ai_generated true

fatal error: concurrent map writes

ID: go/fatal-error-concurrent-map-writes

Also available as: JSON · Markdown · 中文
94%Fix Rate
87%Confidence
1Evidence
2023-02-28First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
go1.20 active — — —
go1.21 active — — —
go1.22 active — — —

Root Cause

Multiple goroutines are writing to the same map without synchronization, triggering Go's runtime race detector.

generic

中文

多个 goroutine 在没有同步的情况下写入同一个映射，触发了 Go 运行时的竞态检测器。

Official Documentation

https://go.dev/doc/articles/race_detector

Workarounds

  1. 94% success Protect the map with a sync.RWMutex: var mu sync.RWMutex; mu.Lock(); m[key] = value; mu.Unlock() 
    Protect the map with a sync.RWMutex: var mu sync.RWMutex; mu.Lock(); m[key] = value; mu.Unlock()
  2. 92% success Use sync.Map for concurrent access: var m sync.Map; m.Store(key, value); value, ok := m.Load(key) 
    Use sync.Map for concurrent access: var m sync.Map; m.Store(key, value); value, ok := m.Load(key)
  3. 90% success Restructure code to use a single goroutine that owns the map and communicates via channels 
    Restructure code to use a single goroutine that owns the map and communicates via channels

中文步骤

  1. 使用 sync.RWMutex 保护映射：var mu sync.RWMutex; mu.Lock(); m[key] = value; mu.Unlock()
  2. 使用 sync.Map 进行并发访问：var m sync.Map; m.Store(key, value); value, ok := m.Load(key)
  3. 重构代码，使用单个 goroutine 拥有映射并通过通道进行通信

Dead Ends

Common approaches that don't work:

  1. Use a map with a mutex but lock only for writes, not reads 70% fail

    Reads without locking can still cause data races and panic

  2. Replace map with sync.Map without understanding its semantics 60% fail

    sync.Map is optimized for specific patterns (append-only, write-once); misuse can be slower or incorrect

  3. Ignore the error and rely on -race flag to catch it later 95% fail

    The error is fatal and crashes the program immediately; cannot be ignored