关于 16.01.md Cond 的例子 about the-golang-standard-library-by-example

[niyanchun]

@lycheng 我再Mac上面测试了一下这个程序，没有问题。但是在Ubuntu上面测会出现你说的这种问题，我debug了一下，看了一下调用栈：

(dlv) bt
0 0x0000000000453693 in runtime.futex
at /usr/local/go/src/runtime/sys_linux_amd64.s:388
1 0x00000000004238de in runtime.futexsleep
at /usr/local/go/src/runtime/os_linux.go:62
2 0x000000000040c370 in runtime.notetsleep_internal
at /usr/local/go/src/runtime/lock_futex.go:174
3 0x000000000040c4e2 in runtime.notetsleepg
at /usr/local/go/src/runtime/lock_futex.go:206
4 0x000000000043fff8 in runtime.timerproc
at /usr/local/go/src/runtime/time.go:209
5 0x00000000004525f0 in runtime.goexit
at /usr/local/go/src/runtime/asm_amd64.s:2086
(dlv) goroutine
Thread 9327 at /usr/local/go/src/runtime/sys_linux_amd64.s:388
Goroutine 15:
Runtime: /usr/local/go/src/runtime/lock_futex.go:206 runtime.notetsleepg (0x40c4e2)
User: /usr/local/go/src/runtime/lock_futex.go:206 runtime.notetsleepg (0x40c4e2)
Go: /usr/local/go/src/runtime/time.go:97 runtime.addtimerLocked (0x43fc2e)
(dlv) goroutines
[15 goroutines]
Goroutine 1 - User: /usr/local/go/src/runtime/time.go:59 time.Sleep (0x43fa55)
Goroutine 2 - User: /usr/local/go/src/runtime/proc.go:260 runtime.gopark (0x4283fa)
Goroutine 3 - User: /usr/local/go/src/runtime/proc.go:260 runtime.gopark (0x4283fa)
Goroutine 4 - User: /usr/local/go/src/runtime/proc.go:260 runtime.gopark (0x4283fa)
Goroutine 5 - User: /usr/local/go/src/runtime/sema.go:267 sync.runtime_notifyListWait (0x436341)
Goroutine 6 - User: /usr/local/go/src/runtime/sema.go:267 sync.runtime_notifyListWait (0x436341)
Goroutine 7 - User: /usr/local/go/src/runtime/sema.go:267 sync.runtime_notifyListWait (0x436341)
Goroutine 8 - User: /usr/local/go/src/runtime/sema.go:267 sync.runtime_notifyListWait (0x436341)
Goroutine 9 - User: /usr/local/go/src/runtime/sema.go:267 sync.runtime_notifyListWait (0x436341)
Goroutine 10 - User: /usr/local/go/src/runtime/sema.go:267 sync.runtime_notifyListWait (0x436341)
Goroutine 11 - User: /usr/local/go/src/runtime/sema.go:267 sync.runtime_notifyListWait (0x436341)
Goroutine 12 - User: /usr/local/go/src/runtime/sema.go:267 sync.runtime_notifyListWait (0x436341)
Goroutine 13 - User: /usr/local/go/src/runtime/sema.go:267 sync.runtime_notifyListWait (0x436341)
Goroutine 14 - User: /usr/local/go/src/runtime/sema.go:267 sync.runtime_notifyListWait (0x436341)

• Goroutine 15 - User: /usr/local/go/src/runtime/lock_futex.go:206 runtime.notetsleepg (0x40c4e2)

有的goroutine卡在没有收到广播信号，所以我想问题出在当main goroutine执行cond.Broadcast()的时候，有的goroutine还没有执行到cond.Wait()。然后我测了一下，如果在main goroutine执行cond.Broadcast()前加上time.Sleep，保证所有的（当然不能完全保证）goroutine都运行到cond.Wait()，这样就不会出现上面的情况了。你可以试一下~

[lycheng]

是的，这个我自己测试的时候发现了

谢谢