How to correctly use sync.Cond?

Question

I\'m having trouble figuring out how to correctly use sync.Cond. From what I can tell, a race condition exists between locking the Locker and invoking the condition\'s Wait meth

Answer 1

You need to make sure that c.Broadcast is called after your call to c.Wait. The correct version of your program would be:

package main

import (
    "fmt"
    "sync"
)

func main() {
    m := &sync.Mutex{}
    c := sync.NewCond(m)
    m.Lock()
    go func() {
        m.Lock() // Wait for c.Wait()
        c.Broadcast()
        m.Unlock()
    }()
    c.Wait() // Unlocks m, waits, then locks m again
    m.Unlock()
}

https://play.golang.org/p/O1r8v8yW6h