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// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build !plan9 && !windows
// +build !plan9,!windows
package main
import (
"os"
"runtime"
"sync/atomic"
"time"
"unsafe"
)
/*
#include <pthread.h>
#include <stdint.h>
extern uint32_t threadExited;
void setExited(void *x);
*/
import "C"
var mainThread C.pthread_t
func init() {
registerInit("LockOSThreadMain", func() {
// init is guaranteed to run on the main thread.
mainThread = C.pthread_self()
})
register("LockOSThreadMain", LockOSThreadMain)
registerInit("LockOSThreadAlt", func() {
// Lock the OS thread now so main runs on the main thread.
runtime.LockOSThread()
})
register("LockOSThreadAlt", LockOSThreadAlt)
}
func LockOSThreadMain() {
// This requires GOMAXPROCS=1 from the beginning to reliably
// start a goroutine on the main thread.
if runtime.GOMAXPROCS(-1) != 1 {
println("requires GOMAXPROCS=1")
os.Exit(1)
}
ready := make(chan bool, 1)
go func() {
// Because GOMAXPROCS=1, this *should* be on the main
// thread. Stay there.
runtime.LockOSThread()
self := C.pthread_self()
if C.pthread_equal(mainThread, self) == 0 {
println("failed to start goroutine on main thread")
os.Exit(1)
}
// Exit with the thread locked, which should exit the
// main thread.
ready <- true
}()
<-ready
time.Sleep(1 * time.Millisecond)
// Check that this goroutine is still running on a different
// thread.
self := C.pthread_self()
if C.pthread_equal(mainThread, self) != 0 {
println("goroutine migrated to locked thread")
os.Exit(1)
}
println("OK")
}
func LockOSThreadAlt() {
// This is running locked to the main OS thread.
var subThread C.pthread_t
ready := make(chan bool, 1)
C.threadExited = 0
go func() {
// This goroutine must be running on a new thread.
runtime.LockOSThread()
subThread = C.pthread_self()
// Register a pthread destructor so we can tell this
// thread has exited.
var key C.pthread_key_t
C.pthread_key_create(&key, (*[0]byte)(unsafe.Pointer(C.setExited)))
C.pthread_setspecific(key, unsafe.Pointer(new(int)))
ready <- true
// Exit with the thread locked.
}()
<-ready
for {
time.Sleep(1 * time.Millisecond)
// Check that this goroutine is running on a different thread.
self := C.pthread_self()
if C.pthread_equal(subThread, self) != 0 {
println("locked thread reused")
os.Exit(1)
}
if atomic.LoadUint32((*uint32)(&C.threadExited)) != 0 {
println("OK")
return
}
}
}
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