mutex_test.go

     1  // Copyright 2012 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 race_test
     6  
     7  import (
     8  	"sync"
     9  	"testing"
    10  	"time"
    11  )
    12  
    13  func TestNoRaceMutex(t *testing.T) {
    14  	var mu sync.Mutex
    15  	var x int16 = 0
    16  	_ = x
    17  	ch := make(chan bool, 2)
    18  	go func() {
    19  		mu.Lock()
    20  		defer mu.Unlock()
    21  		x = 1
    22  		ch <- true
    23  	}()
    24  	go func() {
    25  		mu.Lock()
    26  		x = 2
    27  		mu.Unlock()
    28  		ch <- true
    29  	}()
    30  	<-ch
    31  	<-ch
    32  }
    33  
    34  func TestRaceMutex(t *testing.T) {
    35  	var mu sync.Mutex
    36  	var x int16 = 0
    37  	_ = x
    38  	ch := make(chan bool, 2)
    39  	go func() {
    40  		x = 1
    41  		mu.Lock()
    42  		defer mu.Unlock()
    43  		ch <- true
    44  	}()
    45  	go func() {
    46  		x = 2
    47  		mu.Lock()
    48  		mu.Unlock()
    49  		ch <- true
    50  	}()
    51  	<-ch
    52  	<-ch
    53  }
    54  
    55  func TestRaceMutex2(t *testing.T) {
    56  	var mu1 sync.Mutex
    57  	var mu2 sync.Mutex
    58  	var x int8 = 0
    59  	_ = x
    60  	ch := make(chan bool, 2)
    61  	go func() {
    62  		mu1.Lock()
    63  		defer mu1.Unlock()
    64  		x = 1
    65  		ch <- true
    66  	}()
    67  	go func() {
    68  		mu2.Lock()
    69  		x = 2
    70  		mu2.Unlock()
    71  		ch <- true
    72  	}()
    73  	<-ch
    74  	<-ch
    75  }
    76  
    77  func TestNoRaceMutexPureHappensBefore(t *testing.T) {
    78  	var mu sync.Mutex
    79  	var x int16 = 0
    80  	_ = x
    81  	written := false
    82  	ch := make(chan bool, 2)
    83  	go func() {
    84  		x = 1
    85  		mu.Lock()
    86  		written = true
    87  		mu.Unlock()
    88  		ch <- true
    89  	}()
    90  	go func() {
    91  		time.Sleep(100 * time.Microsecond)
    92  		mu.Lock()
    93  		for !written {
    94  			mu.Unlock()
    95  			time.Sleep(100 * time.Microsecond)
    96  			mu.Lock()
    97  		}
    98  		mu.Unlock()
    99  		x = 1
   100  		ch <- true
   101  	}()
   102  	<-ch
   103  	<-ch
   104  }
   105  
   106  func TestNoRaceMutexSemaphore(t *testing.T) {
   107  	var mu sync.Mutex
   108  	ch := make(chan bool, 2)
   109  	x := 0
   110  	_ = x
   111  	mu.Lock()
   112  	go func() {
   113  		x = 1
   114  		mu.Unlock()
   115  		ch <- true
   116  	}()
   117  	go func() {
   118  		mu.Lock()
   119  		x = 2
   120  		mu.Unlock()
   121  		ch <- true
   122  	}()
   123  	<-ch
   124  	<-ch
   125  }
   126  
   127  // from doc/go_mem.html
   128  func TestNoRaceMutexExampleFromHtml(t *testing.T) {
   129  	var l sync.Mutex
   130  	a := ""
   131  
   132  	l.Lock()
   133  	go func() {
   134  		a = "hello, world"
   135  		l.Unlock()
   136  	}()
   137  	l.Lock()
   138  	_ = a
   139  }
   140  
   141  func TestRaceMutexOverwrite(t *testing.T) {
   142  	c := make(chan bool, 1)
   143  	var mu sync.Mutex
   144  	go func() {
   145  		mu = sync.Mutex{}
   146  		c <- true
   147  	}()
   148  	mu.Lock()
   149  	<-c
   150  }
   151
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