github.com/likebike/go--@v0.0.0-20190911215757-0bd925d16e96/go/src/runtime/testdata/testprog/lockosthread.go (about)

     1  // Copyright 2017 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package main
     6  
     7  import (
     8  	"os"
     9  	"runtime"
    10  	"time"
    11  )
    12  
    13  var mainTID int
    14  
    15  func init() {
    16  	registerInit("LockOSThreadMain", func() {
    17  		// init is guaranteed to run on the main thread.
    18  		mainTID = gettid()
    19  	})
    20  	register("LockOSThreadMain", LockOSThreadMain)
    21  
    22  	registerInit("LockOSThreadAlt", func() {
    23  		// Lock the OS thread now so main runs on the main thread.
    24  		runtime.LockOSThread()
    25  	})
    26  	register("LockOSThreadAlt", LockOSThreadAlt)
    27  }
    28  
    29  func LockOSThreadMain() {
    30  	// gettid only works on Linux, so on other platforms this just
    31  	// checks that the runtime doesn't do anything terrible.
    32  
    33  	// This requires GOMAXPROCS=1 from the beginning to reliably
    34  	// start a goroutine on the main thread.
    35  	if runtime.GOMAXPROCS(-1) != 1 {
    36  		println("requires GOMAXPROCS=1")
    37  		os.Exit(1)
    38  	}
    39  
    40  	ready := make(chan bool, 1)
    41  	go func() {
    42  		// Because GOMAXPROCS=1, this *should* be on the main
    43  		// thread. Stay there.
    44  		runtime.LockOSThread()
    45  		if mainTID != 0 && gettid() != mainTID {
    46  			println("failed to start goroutine on main thread")
    47  			os.Exit(1)
    48  		}
    49  		// Exit with the thread locked, which should exit the
    50  		// main thread.
    51  		ready <- true
    52  	}()
    53  	<-ready
    54  	time.Sleep(1 * time.Millisecond)
    55  	// Check that this goroutine is still running on a different
    56  	// thread.
    57  	if mainTID != 0 && gettid() == mainTID {
    58  		println("goroutine migrated to locked thread")
    59  		os.Exit(1)
    60  	}
    61  	println("OK")
    62  }
    63  
    64  func LockOSThreadAlt() {
    65  	// This is running locked to the main OS thread.
    66  
    67  	var subTID int
    68  	ready := make(chan bool, 1)
    69  	go func() {
    70  		// This goroutine must be running on a new thread.
    71  		runtime.LockOSThread()
    72  		subTID = gettid()
    73  		ready <- true
    74  		// Exit with the thread locked.
    75  	}()
    76  	<-ready
    77  	runtime.UnlockOSThread()
    78  	for i := 0; i < 100; i++ {
    79  		time.Sleep(1 * time.Millisecond)
    80  		// Check that this goroutine is running on a different thread.
    81  		if subTID != 0 && gettid() == subTID {
    82  			println("locked thread reused")
    83  			os.Exit(1)
    84  		}
    85  		exists, supported := tidExists(subTID)
    86  		if !supported || !exists {
    87  			goto ok
    88  		}
    89  	}
    90  	println("sub thread", subTID, "still running")
    91  	return
    92  ok:
    93  	println("OK")
    94  }