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Source file src/runtime/internal/atomic/atomic_test.go

Documentation: runtime/internal/atomic

  // Copyright 2015 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package atomic_test
  
  import (
  	"runtime"
  	"runtime/internal/atomic"
  	"runtime/internal/sys"
  	"testing"
  	"unsafe"
  )
  
  func runParallel(N, iter int, f func()) {
  	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(int(N)))
  	done := make(chan bool)
  	for i := 0; i < N; i++ {
  		go func() {
  			for j := 0; j < iter; j++ {
  				f()
  			}
  			done <- true
  		}()
  	}
  	for i := 0; i < N; i++ {
  		<-done
  	}
  }
  
  func TestXadduintptr(t *testing.T) {
  	const N = 20
  	const iter = 100000
  	inc := uintptr(100)
  	total := uintptr(0)
  	runParallel(N, iter, func() {
  		atomic.Xadduintptr(&total, inc)
  	})
  	if want := uintptr(N * iter * inc); want != total {
  		t.Fatalf("xadduintpr error, want %d, got %d", want, total)
  	}
  	total = 0
  	runParallel(N, iter, func() {
  		atomic.Xadduintptr(&total, inc)
  		atomic.Xadduintptr(&total, uintptr(-int64(inc)))
  	})
  	if total != 0 {
  		t.Fatalf("xadduintpr total error, want %d, got %d", 0, total)
  	}
  }
  
  // Tests that xadduintptr correctly updates 64-bit values. The place where
  // we actually do so is mstats.go, functions mSysStat{Inc,Dec}.
  func TestXadduintptrOnUint64(t *testing.T) {
  	if sys.BigEndian != 0 {
  		// On big endian architectures, we never use xadduintptr to update
  		// 64-bit values and hence we skip the test.  (Note that functions
  		// mSysStat{Inc,Dec} in mstats.go have explicit checks for
  		// big-endianness.)
  		t.Skip("skip xadduintptr on big endian architecture")
  	}
  	const inc = 100
  	val := uint64(0)
  	atomic.Xadduintptr((*uintptr)(unsafe.Pointer(&val)), inc)
  	if inc != val {
  		t.Fatalf("xadduintptr should increase lower-order bits, want %d, got %d", inc, val)
  	}
  }
  
  func shouldPanic(t *testing.T, name string, f func()) {
  	defer func() {
  		if recover() == nil {
  			t.Errorf("%s did not panic", name)
  		}
  	}()
  	f()
  }
  
  // Variant of sync/atomic's TestUnaligned64:
  func TestUnaligned64(t *testing.T) {
  	// Unaligned 64-bit atomics on 32-bit systems are
  	// a continual source of pain. Test that on 32-bit systems they crash
  	// instead of failing silently.
  
  	switch runtime.GOARCH {
  	default:
  		if unsafe.Sizeof(int(0)) != 4 {
  			t.Skip("test only runs on 32-bit systems")
  		}
  	case "amd64p32":
  		// amd64p32 can handle unaligned atomics.
  		t.Skipf("test not needed on %v", runtime.GOARCH)
  	}
  
  	x := make([]uint32, 4)
  	up64 := (*uint64)(unsafe.Pointer(&x[1])) // misaligned
  	p64 := (*int64)(unsafe.Pointer(&x[1]))   // misaligned
  
  	shouldPanic(t, "Load64", func() { atomic.Load64(up64) })
  	shouldPanic(t, "Loadint64", func() { atomic.Loadint64(p64) })
  	shouldPanic(t, "Store64", func() { atomic.Store64(up64, 0) })
  	shouldPanic(t, "Xadd64", func() { atomic.Xadd64(up64, 1) })
  	shouldPanic(t, "Xchg64", func() { atomic.Xchg64(up64, 1) })
  	shouldPanic(t, "Cas64", func() { atomic.Cas64(up64, 1, 2) })
  }
  

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