atomic_test.go

Documentation: internal/runtime/atomic

     1  // Copyright 2015 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 atomic_test
     6  
     7  import (
     8  	"internal/goarch"
     9  	"internal/runtime/atomic"
    10  	"runtime"
    11  	"testing"
    12  	"unsafe"
    13  )
    14  
    15  func runParallel(N, iter int, f func()) {
    16  	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(int(N)))
    17  	done := make(chan bool)
    18  	for i := 0; i < N; i++ {
    19  		go func() {
    20  			for j := 0; j < iter; j++ {
    21  				f()
    22  			}
    23  			done <- true
    24  		}()
    25  	}
    26  	for i := 0; i < N; i++ {
    27  		<-done
    28  	}
    29  }
    30  
    31  func TestXadduintptr(t *testing.T) {
    32  	N := 20
    33  	iter := 100000
    34  	if testing.Short() {
    35  		N = 10
    36  		iter = 10000
    37  	}
    38  	inc := uintptr(100)
    39  	total := uintptr(0)
    40  	runParallel(N, iter, func() {
    41  		atomic.Xadduintptr(&total, inc)
    42  	})
    43  	if want := uintptr(N*iter) * inc; want != total {
    44  		t.Fatalf("xadduintpr error, want %d, got %d", want, total)
    45  	}
    46  	total = 0
    47  	runParallel(N, iter, func() {
    48  		atomic.Xadduintptr(&total, inc)
    49  		atomic.Xadduintptr(&total, uintptr(-int64(inc)))
    50  	})
    51  	if total != 0 {
    52  		t.Fatalf("xadduintpr total error, want %d, got %d", 0, total)
    53  	}
    54  }
    55  
    56  // Tests that xadduintptr correctly updates 64-bit values. The place where
    57  // we actually do so is mstats.go, functions mSysStat{Inc,Dec}.
    58  func TestXadduintptrOnUint64(t *testing.T) {
    59  	if goarch.BigEndian {
    60  		// On big endian architectures, we never use xadduintptr to update
    61  		// 64-bit values and hence we skip the test.  (Note that functions
    62  		// mSysStat{Inc,Dec} in mstats.go have explicit checks for
    63  		// big-endianness.)
    64  		t.Skip("skip xadduintptr on big endian architecture")
    65  	}
    66  	const inc = 100
    67  	val := uint64(0)
    68  	atomic.Xadduintptr((*uintptr)(unsafe.Pointer(&val)), inc)
    69  	if inc != val {
    70  		t.Fatalf("xadduintptr should increase lower-order bits, want %d, got %d", inc, val)
    71  	}
    72  }
    73  
    74  func shouldPanic(t *testing.T, name string, f func()) {
    75  	defer func() {
    76  		// Check that all GC maps are sane.
    77  		runtime.GC()
    78  
    79  		err := recover()
    80  		want := "unaligned 64-bit atomic operation"
    81  		if err == nil {
    82  			t.Errorf("%s did not panic", name)
    83  		} else if s, _ := err.(string); s != want {
    84  			t.Errorf("%s: wanted panic %q, got %q", name, want, err)
    85  		}
    86  	}()
    87  	f()
    88  }
    89  
    90  // Variant of sync/atomic's TestUnaligned64:
    91  func TestUnaligned64(t *testing.T) {
    92  	// Unaligned 64-bit atomics on 32-bit systems are
    93  	// a continual source of pain. Test that on 32-bit systems they crash
    94  	// instead of failing silently.
    95  
    96  	if unsafe.Sizeof(int(0)) != 4 {
    97  		t.Skip("test only runs on 32-bit systems")
    98  	}
    99  
   100  	x := make([]uint32, 4)
   101  	u := unsafe.Pointer(uintptr(unsafe.Pointer(&x[0])) | 4) // force alignment to 4
   102  
   103  	up64 := (*uint64)(u) // misaligned
   104  	p64 := (*int64)(u)   // misaligned
   105  
   106  	shouldPanic(t, "Load64", func() { atomic.Load64(up64) })
   107  	shouldPanic(t, "Loadint64", func() { atomic.Loadint64(p64) })
   108  	shouldPanic(t, "Store64", func() { atomic.Store64(up64, 0) })
   109  	shouldPanic(t, "Xadd64", func() { atomic.Xadd64(up64, 1) })
   110  	shouldPanic(t, "Xchg64", func() { atomic.Xchg64(up64, 1) })
   111  	shouldPanic(t, "Cas64", func() { atomic.Cas64(up64, 1, 2) })
   112  }
   113  
   114  func TestAnd8(t *testing.T) {
   115  	// Basic sanity check.
   116  	x := uint8(0xff)
   117  	for i := uint8(0); i < 8; i++ {
   118  		atomic.And8(&x, ^(1 << i))
   119  		if r := uint8(0xff) << (i + 1); x != r {
   120  			t.Fatalf("clearing bit %#x: want %#x, got %#x", uint8(1<<i), r, x)
   121  		}
   122  	}
   123  
   124  	// Set every bit in array to 1.
   125  	a := make([]uint8, 1<<12)
   126  	for i := range a {
   127  		a[i] = 0xff
   128  	}
   129  
   130  	// Clear array bit-by-bit in different goroutines.
   131  	done := make(chan bool)
   132  	for i := 0; i < 8; i++ {
   133  		m := ^uint8(1 << i)
   134  		go func() {
   135  			for i := range a {
   136  				atomic.And8(&a[i], m)
   137  			}
   138  			done <- true
   139  		}()
   140  	}
   141  	for i := 0; i < 8; i++ {
   142  		<-done
   143  	}
   144  
   145  	// Check that the array has been totally cleared.
   146  	for i, v := range a {
   147  		if v != 0 {
   148  			t.Fatalf("a[%v] not cleared: want %#x, got %#x", i, uint8(0), v)
   149  		}
   150  	}
   151  }
   152  
   153  func TestAnd(t *testing.T) {
   154  	// Basic sanity check.
   155  	x := uint32(0xffffffff)
   156  	for i := uint32(0); i < 32; i++ {
   157  		atomic.And(&x, ^(1 << i))
   158  		if r := uint32(0xffffffff) << (i + 1); x != r {
   159  			t.Fatalf("clearing bit %#x: want %#x, got %#x", uint32(1<<i), r, x)
   160  		}
   161  	}
   162  
   163  	// Set every bit in array to 1.
   164  	a := make([]uint32, 1<<12)
   165  	for i := range a {
   166  		a[i] = 0xffffffff
   167  	}
   168  
   169  	// Clear array bit-by-bit in different goroutines.
   170  	done := make(chan bool)
   171  	for i := 0; i < 32; i++ {
   172  		m := ^uint32(1 << i)
   173  		go func() {
   174  			for i := range a {
   175  				atomic.And(&a[i], m)
   176  			}
   177  			done <- true
   178  		}()
   179  	}
   180  	for i := 0; i < 32; i++ {
   181  		<-done
   182  	}
   183  
   184  	// Check that the array has been totally cleared.
   185  	for i, v := range a {
   186  		if v != 0 {
   187  			t.Fatalf("a[%v] not cleared: want %#x, got %#x", i, uint32(0), v)
   188  		}
   189  	}
   190  }
   191  
   192  func TestOr8(t *testing.T) {
   193  	// Basic sanity check.
   194  	x := uint8(0)
   195  	for i := uint8(0); i < 8; i++ {
   196  		atomic.Or8(&x, 1<<i)
   197  		if r := (uint8(1) << (i + 1)) - 1; x != r {
   198  			t.Fatalf("setting bit %#x: want %#x, got %#x", uint8(1)<<i, r, x)
   199  		}
   200  	}
   201  
   202  	// Start with every bit in array set to 0.
   203  	a := make([]uint8, 1<<12)
   204  
   205  	// Set every bit in array bit-by-bit in different goroutines.
   206  	done := make(chan bool)
   207  	for i := 0; i < 8; i++ {
   208  		m := uint8(1 << i)
   209  		go func() {
   210  			for i := range a {
   211  				atomic.Or8(&a[i], m)
   212  			}
   213  			done <- true
   214  		}()
   215  	}
   216  	for i := 0; i < 8; i++ {
   217  		<-done
   218  	}
   219  
   220  	// Check that the array has been totally set.
   221  	for i, v := range a {
   222  		if v != 0xff {
   223  			t.Fatalf("a[%v] not fully set: want %#x, got %#x", i, uint8(0xff), v)
   224  		}
   225  	}
   226  }
   227  
   228  func TestOr(t *testing.T) {
   229  	// Basic sanity check.
   230  	x := uint32(0)
   231  	for i := uint32(0); i < 32; i++ {
   232  		atomic.Or(&x, 1<<i)
   233  		if r := (uint32(1) << (i + 1)) - 1; x != r {
   234  			t.Fatalf("setting bit %#x: want %#x, got %#x", uint32(1)<<i, r, x)
   235  		}
   236  	}
   237  
   238  	// Start with every bit in array set to 0.
   239  	a := make([]uint32, 1<<12)
   240  
   241  	// Set every bit in array bit-by-bit in different goroutines.
   242  	done := make(chan bool)
   243  	for i := 0; i < 32; i++ {
   244  		m := uint32(1 << i)
   245  		go func() {
   246  			for i := range a {
   247  				atomic.Or(&a[i], m)
   248  			}
   249  			done <- true
   250  		}()
   251  	}
   252  	for i := 0; i < 32; i++ {
   253  		<-done
   254  	}
   255  
   256  	// Check that the array has been totally set.
   257  	for i, v := range a {
   258  		if v != 0xffffffff {
   259  			t.Fatalf("a[%v] not fully set: want %#x, got %#x", i, uint32(0xffffffff), v)
   260  		}
   261  	}
   262  }
   263  
   264  func TestBitwiseContended8(t *testing.T) {
   265  	// Start with every bit in array set to 0.
   266  	a := make([]uint8, 16)
   267  
   268  	// Iterations to try.
   269  	N := 1 << 16
   270  	if testing.Short() {
   271  		N = 1 << 10
   272  	}
   273  
   274  	// Set and then clear every bit in the array bit-by-bit in different goroutines.
   275  	done := make(chan bool)
   276  	for i := 0; i < 8; i++ {
   277  		m := uint8(1 << i)
   278  		go func() {
   279  			for n := 0; n < N; n++ {
   280  				for i := range a {
   281  					atomic.Or8(&a[i], m)
   282  					if atomic.Load8(&a[i])&m != m {
   283  						t.Errorf("a[%v] bit %#x not set", i, m)
   284  					}
   285  					atomic.And8(&a[i], ^m)
   286  					if atomic.Load8(&a[i])&m != 0 {
   287  						t.Errorf("a[%v] bit %#x not clear", i, m)
   288  					}
   289  				}
   290  			}
   291  			done <- true
   292  		}()
   293  	}
   294  	for i := 0; i < 8; i++ {
   295  		<-done
   296  	}
   297  
   298  	// Check that the array has been totally cleared.
   299  	for i, v := range a {
   300  		if v != 0 {
   301  			t.Fatalf("a[%v] not cleared: want %#x, got %#x", i, uint8(0), v)
   302  		}
   303  	}
   304  }
   305  
   306  func TestBitwiseContended(t *testing.T) {
   307  	// Start with every bit in array set to 0.
   308  	a := make([]uint32, 16)
   309  
   310  	// Iterations to try.
   311  	N := 1 << 16
   312  	if testing.Short() {
   313  		N = 1 << 10
   314  	}
   315  
   316  	// Set and then clear every bit in the array bit-by-bit in different goroutines.
   317  	done := make(chan bool)
   318  	for i := 0; i < 32; i++ {
   319  		m := uint32(1 << i)
   320  		go func() {
   321  			for n := 0; n < N; n++ {
   322  				for i := range a {
   323  					atomic.Or(&a[i], m)
   324  					if atomic.Load(&a[i])&m != m {
   325  						t.Errorf("a[%v] bit %#x not set", i, m)
   326  					}
   327  					atomic.And(&a[i], ^m)
   328  					if atomic.Load(&a[i])&m != 0 {
   329  						t.Errorf("a[%v] bit %#x not clear", i, m)
   330  					}
   331  				}
   332  			}
   333  			done <- true
   334  		}()
   335  	}
   336  	for i := 0; i < 32; i++ {
   337  		<-done
   338  	}
   339  
   340  	// Check that the array has been totally cleared.
   341  	for i, v := range a {
   342  		if v != 0 {
   343  			t.Fatalf("a[%v] not cleared: want %#x, got %#x", i, uint32(0), v)
   344  		}
   345  	}
   346  }
   347  
   348  func TestCasRel(t *testing.T) {
   349  	const _magic = 0x5a5aa5a5
   350  	var x struct {
   351  		before uint32
   352  		i      uint32
   353  		after  uint32
   354  		o      uint32
   355  		n      uint32
   356  	}
   357  
   358  	x.before = _magic
   359  	x.after = _magic
   360  	for j := 0; j < 32; j += 1 {
   361  		x.i = (1 << j) + 0
   362  		x.o = (1 << j) + 0
   363  		x.n = (1 << j) + 1
   364  		if !atomic.CasRel(&x.i, x.o, x.n) {
   365  			t.Fatalf("should have swapped %#x %#x", x.o, x.n)
   366  		}
   367  
   368  		if x.i != x.n {
   369  			t.Fatalf("wrong x.i after swap: x.i=%#x x.n=%#x", x.i, x.n)
   370  		}
   371  
   372  		if x.before != _magic || x.after != _magic {
   373  			t.Fatalf("wrong magic: %#x _ %#x != %#x _ %#x", x.before, x.after, _magic, _magic)
   374  		}
   375  	}
   376  }
   377  
   378  func TestStorepNoWB(t *testing.T) {
   379  	var p [2]*int
   380  	for i := range p {
   381  		atomic.StorepNoWB(unsafe.Pointer(&p[i]), unsafe.Pointer(new(int)))
   382  	}
   383  	if p[0] == p[1] {
   384  		t.Error("Bad escape analysis of StorepNoWB")
   385  	}
   386  }
   387
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