并行执行Go例程的问题

Question

In my code there are three concurrent routines. I try to give a brief overview of my code,

Routine 1 {
do something

*Send int to Routine 2
Send int to Routine 3
Print Something
Print Something*

do something
}

Routine 2 {
do something

*Send int to Routine 1
Send int to Routine 3
Print Something
Print Something*

do something
}

Routine 3 {
do something

*Send int to Routine 1
Send int to Routine 2
Print Something
Print Something*

do something
}

main {
routine1
routine2
routine3
}

I want that, while codes between two do something (codes between two star marks) is executing, flow of control must not go to other go routines. For example, when routine1 is executing the events between two stars (sending and printing events), routine 2 and 3 must be blocked (means flow of execution does not pass to routine 2 or 3 from routine 1).After completing last print event, flow of execution may pass to routine 2 or 3.Can anybody help me by specifying, how can I achieve this ? Is it possible to implement above specification by WaitGroup ? Can anybody show me by giving a simple example how to implement above specified example by using WaitGroup. Thanks.

NB:May be this is repeat question of this. I tried by using that sync-lock mechanism, however, may be because I have a large code that's why I could not put lock-unlock properly, and it's creating deadlock situation (or may be my method is error producing). Can anybody help me by a simple procedure thus I can achieve this. I give a simple example of my code here where Here I want to put two prints and sending event inside mutex (for routine 1) thus routine 2 can't interrupt it. Can you help me how is it possible. One possible solution given, http://play.golang.org/p/-uoQSqBJKS which gives error.

Answer 1

Why do you want to do this?

The deadlock problem is, if you don't allow other goroutines to be scheduled, then your channel sends can't proceed, unless there's buffering. Go's channels have finite buffering, so you end up with a race condition on draining before they get sent on while full. You could introduce infinite buffering, or put each send in its own goroutine, but it again comes down to: why are you trying to do this; what are you trying to achieve?

Another thing: if you only want to ensure mutual exclusion of the three sets of code between *s, then yes, you can use mutexes. If you want to ensure that no code interrupts your block, regardless of where it was suspended, then you might need to use runtime.LockOSThread and runtime.UnlockOSThread. These are fairly low level and you need to know what you're doing, and they're rarely needed. Of you want there to be no other goroutines running, you'll have to have runtime.GOMAXPROCS(1), which is currently the default.