Go调度程序是否还管理运行时创建的非Go线程？

Question

As far as I know, Go runtime scheduler manages some number of OS Threads(probably more than GOMAXPROCS?) and Go routines by assigning Go routines to OS Threads continuously.

So this basically means that the execution of Go routines, including main goroutine , are managed by both of go scheduler and OS' thread scheudling.

Now here's my questions..

1. Does the execution of goroutine fully managed by OS' thread scheduling if I call runtime.LockOSThread() at the start of that goroutine?

2. Does the execution of non-Go thread also fully managed by OS' thread scheduling? In other words, if I create a non-Go Thread by CreateThread function (Windows), then the management non-Go Thread's execution is out of scope of Go's runtime scheduler?

3. What if I launch another goroutine with go func() in that non-Go Thread? How that non-Go Thread and goroutine's execution is managed?

4. Currently, I'm writing a program in Golang which runs a windows message loop in main() function of go program. Most of the time it worked well, but sometimes the message loop get blocked and resumed after few seconds and then large amount of old messages get pumped. (My another question: Windows Message Loop is getting blocked and resumed intermittently (golang))

   I had no idea why it occurs, so I suspected main goroutine's OS Thread switch by go scheduler. So I added runtime.LockOSThread() at the start of main() function to ensure windows message loop always run in the same thread. However, the problem still occured!

   I still have no idea why it occurs, but I'm suspecting this is because of Go scheduler because the same logic written in Python 3.4 didn't make any problems like this.

   So what I'm trying now is creating a new Windows Thread (non-Go Thread) by calling CreateThread(...) function, and running windows message loop in that thread.

   But I'm curious that whether this approach is different with calling runtime.LockOSThread() in main goroutine running windows message loop from Go runtime scheduler's perspective.

   So my question is, 'If I create a new non-Go Thread with CreateThread(...) function and run windows message loop in that thread, then does execution of that thread not affected by Go's runtime scheduler?'

Any helps or ideas will be greatly appreciated. Thanks.

Answer 1

If you run a new OS thread using the CreateThread() routine, Go's scheduler will not touch the thread. However, you will then have to implement a way for that thread to communicate with Goroutines. You can't, for instance, call a Go method directly from the thread created by CreateThread(). Instead, you will have to use some C-based system to poll events from a Goroutine.

As an aside, if you want to run the loop from the main OS thread, you should call LockOSThread() in init() rather than in main(). See https://github.com/golang/go/wiki/LockOSThread:

func init() {
    runtime.LockOSThread();
}
func main() {
    // Run loop here.
}