futex_test.go

Documentation: runtime

     1  // Copyright 2013 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  // Futex is only available on DragonFly BSD, FreeBSD and Linux.
     6  // The race detector emits calls to split stack functions so it breaks
     7  // the test.
     8  
     9  //go:build (dragonfly || freebsd || linux) && !race
    10  // +build dragonfly freebsd linux
    11  // +build !race
    12  
    13  package runtime_test
    14  
    15  import (
    16  	"runtime"
    17  	"sync"
    18  	"sync/atomic"
    19  	"testing"
    20  	"time"
    21  )
    22  
    23  type futexsleepTest struct {
    24  	mtx uint32
    25  	ns  int64
    26  	msg string
    27  	ch  chan *futexsleepTest
    28  }
    29  
    30  var futexsleepTests = []futexsleepTest{
    31  	beforeY2038: {mtx: 0, ns: 86400 * 1e9, msg: "before the year 2038"},
    32  	afterY2038:  {mtx: 0, ns: (1<<31 + 100) * 1e9, msg: "after the year 2038"},
    33  }
    34  
    35  const (
    36  	beforeY2038 = iota
    37  	afterY2038
    38  )
    39  
    40  func TestFutexsleep(t *testing.T) {
    41  	if runtime.GOMAXPROCS(0) > 1 {
    42  		// futexsleep doesn't handle EINTR or other signals,
    43  		// so spurious wakeups may happen.
    44  		t.Skip("skipping; GOMAXPROCS>1")
    45  	}
    46  
    47  	start := time.Now()
    48  	var wg sync.WaitGroup
    49  	for i := range futexsleepTests {
    50  		tt := &futexsleepTests[i]
    51  		tt.mtx = 0
    52  		tt.ch = make(chan *futexsleepTest, 1)
    53  		wg.Add(1)
    54  		go func(tt *futexsleepTest) {
    55  			runtime.Entersyscall()
    56  			runtime.Futexsleep(&tt.mtx, 0, tt.ns)
    57  			runtime.Exitsyscall()
    58  			tt.ch <- tt
    59  			wg.Done()
    60  		}(tt)
    61  	}
    62  loop:
    63  	for {
    64  		select {
    65  		case tt := <-futexsleepTests[beforeY2038].ch:
    66  			t.Errorf("futexsleep test %q finished early after %s", tt.msg, time.Since(start))
    67  			break loop
    68  		case tt := <-futexsleepTests[afterY2038].ch:
    69  			// Looks like FreeBSD 10 kernel has changed
    70  			// the semantics of timedwait on userspace
    71  			// mutex to make broken stuff look broken.
    72  			switch {
    73  			case runtime.GOOS == "freebsd" && runtime.GOARCH == "386":
    74  				t.Log("freebsd/386 may not work correctly after the year 2038, see golang.org/issue/7194")
    75  			default:
    76  				t.Errorf("futexsleep test %q finished early after %s", tt.msg, time.Since(start))
    77  				break loop
    78  			}
    79  		case <-time.After(time.Second):
    80  			break loop
    81  		}
    82  	}
    83  	for i := range futexsleepTests {
    84  		tt := &futexsleepTests[i]
    85  		atomic.StoreUint32(&tt.mtx, 1)
    86  		runtime.Futexwakeup(&tt.mtx, 1)
    87  	}
    88  	wg.Wait()
    89  }
    90
View as plain text