go runtime_error ai_generated true

fatal error: concurrent map read and map write

ID: go/concurrent-map-read-and-write

Also available as: JSON · Markdown · 中文
80%Fix Rate
90%Confidence
0Evidence
2024-03-05First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.18 active — — —
1.21 active — — —

Root Cause

One goroutine read a map while another wrote to it. The runtime's map implementation detects this inconsistent access and aborts the program.

generic

中文

一个 goroutine 读 map 的同时另一个 goroutine 写同一个 map。运行时检测到这种不一致访问会终止程序。

Workarounds

  1. 93% success 
    var mu sync.RWMutex
// writer
mu.Lock(); m[k]=v; mu.Unlock()
// reader
mu.RLock(); v := m[k]; mu.RUnlock()
  2. 85% success 
    type req struct{ key string; resp chan int }
// single owner goroutine processes reqs serially

Dead Ends

Common approaches that don't work:

  1. 85% fail

    Copying a map being concurrently written also races and may panic or produce corrupted data.

  2. 87% fail

    Timing-based synchronization is unreliable and breaks under load or different GOMAXPROCS.