github.com/hlts2/go@v0.0.0-20170904000733-812b34efaed8/src/runtime/race/testdata/rwmutex_test.go (about)

     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 TestRaceMutexRWMutex(t *testing.T) {
    14  	var mu1 sync.Mutex
    15  	var mu2 sync.RWMutex
    16  	var x int16 = 0
    17  	ch := make(chan bool, 2)
    18  	go func() {
    19  		mu1.Lock()
    20  		defer mu1.Unlock()
    21  		x = 1
    22  		ch <- true
    23  	}()
    24  	go func() {
    25  		mu2.Lock()
    26  		x = 2
    27  		mu2.Unlock()
    28  		ch <- true
    29  	}()
    30  	<-ch
    31  	<-ch
    32  }
    33  
    34  func TestNoRaceRWMutex(t *testing.T) {
    35  	var mu sync.RWMutex
    36  	var x, y int64 = 0, 1
    37  	ch := make(chan bool, 2)
    38  	go func() {
    39  		mu.Lock()
    40  		defer mu.Unlock()
    41  		x = 2
    42  		ch <- true
    43  	}()
    44  	go func() {
    45  		mu.RLock()
    46  		y = x
    47  		mu.RUnlock()
    48  		ch <- true
    49  	}()
    50  	<-ch
    51  	<-ch
    52  }
    53  
    54  func TestRaceRWMutexMultipleReaders(t *testing.T) {
    55  	var mu sync.RWMutex
    56  	var x, y int64 = 0, 1
    57  	ch := make(chan bool, 4)
    58  	go func() {
    59  		mu.Lock()
    60  		defer mu.Unlock()
    61  		x = 2
    62  		ch <- true
    63  	}()
    64  	// Use three readers so that no matter what order they're
    65  	// scheduled in, two will be on the same side of the write
    66  	// lock above.
    67  	go func() {
    68  		mu.RLock()
    69  		y = x + 1
    70  		mu.RUnlock()
    71  		ch <- true
    72  	}()
    73  	go func() {
    74  		mu.RLock()
    75  		y = x + 2
    76  		mu.RUnlock()
    77  		ch <- true
    78  	}()
    79  	go func() {
    80  		mu.RLock()
    81  		y = x + 3
    82  		mu.RUnlock()
    83  		ch <- true
    84  	}()
    85  	<-ch
    86  	<-ch
    87  	<-ch
    88  	<-ch
    89  	_ = y
    90  }
    91  
    92  func TestNoRaceRWMutexMultipleReaders(t *testing.T) {
    93  	var mu sync.RWMutex
    94  	x := int64(0)
    95  	ch := make(chan bool, 4)
    96  	go func() {
    97  		mu.Lock()
    98  		defer mu.Unlock()
    99  		x = 2
   100  		ch <- true
   101  	}()
   102  	go func() {
   103  		mu.RLock()
   104  		y := x + 1
   105  		_ = y
   106  		mu.RUnlock()
   107  		ch <- true
   108  	}()
   109  	go func() {
   110  		mu.RLock()
   111  		y := x + 2
   112  		_ = y
   113  		mu.RUnlock()
   114  		ch <- true
   115  	}()
   116  	go func() {
   117  		mu.RLock()
   118  		y := x + 3
   119  		_ = y
   120  		mu.RUnlock()
   121  		ch <- true
   122  	}()
   123  	<-ch
   124  	<-ch
   125  	<-ch
   126  	<-ch
   127  }
   128  
   129  func TestNoRaceRWMutexTransitive(t *testing.T) {
   130  	var mu sync.RWMutex
   131  	x := int64(0)
   132  	ch := make(chan bool, 2)
   133  	go func() {
   134  		mu.RLock()
   135  		_ = x
   136  		mu.RUnlock()
   137  		ch <- true
   138  	}()
   139  	go func() {
   140  		time.Sleep(1e7)
   141  		mu.RLock()
   142  		_ = x
   143  		mu.RUnlock()
   144  		ch <- true
   145  	}()
   146  	time.Sleep(2e7)
   147  	mu.Lock()
   148  	x = 42
   149  	mu.Unlock()
   150  	<-ch
   151  	<-ch
   152  }