Does runtime.LockOSThread allow child goroutines to run in same OS thread?

Question

I understand that in Go, runtime.LockOSThread() will bind a goroutine to one OS thread and not allow other goroutines to execute in that thread. Is this also true for child goro

Answer 1

We can check it using pthread.h's pthread_self:

package main

// #include 
import "C"
import (
    "fmt"
    "runtime"
)

func main() {
    runtime.GOMAXPROCS(runtime.NumCPU())
    ch1 := make(chan bool)
    ch2 := make(chan bool)
    fmt.Println("main", C.pthread_self())
    go func() {
        runtime.LockOSThread()
        fmt.Println("locked", C.pthread_self())
        go func() {
            fmt.Println("locked child", C.pthread_self())
            ch1 <- true
        }()
        ch2 <- true
    }()
    <-ch1
    <-ch2
}

On my machine it prints something like this, main and locked always being sometimes the same, but sometimes different:

main 139711253194560
locked 139711219787520
locked child 139711236572928

EDIT I forgot about GOMAXPROCS. Added, the results are varying now.