1 files changed, 160 insertions, 0 deletions
diff --git a/src/cmd/go/internal/renameio/renameio_test.go b/src/cmd/go/internal/renameio/renameio_test.go
new file mode 100644
index 0000000..5b2ed83
--- /dev/null
+++ b/src/cmd/go/internal/renameio/renameio_test.go
@@ -0,0 +1,160 @@
+// Copyright 2019 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.
+
+// +build !plan9
+
+package renameio
+
+import (
+	"encoding/binary"
+	"errors"
+	"internal/testenv"
+	"math/rand"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"syscall"
+	"testing"
+	"time"
+
+	"cmd/go/internal/robustio"
+)
+
+func TestConcurrentReadsAndWrites(t *testing.T) {
+	if runtime.GOOS == "darwin" && strings.HasSuffix(testenv.Builder(), "-10_14") {
+		testenv.SkipFlaky(t, 33041)
+	}
+
+	dir, err := os.MkdirTemp("", "renameio")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+	path := filepath.Join(dir, "blob.bin")
+
+	const chunkWords = 8 << 10
+	buf := make([]byte, 2*chunkWords*8)
+	for i := uint64(0); i < 2*chunkWords; i++ {
+		binary.LittleEndian.PutUint64(buf[i*8:], i)
+	}
+
+	var attempts int64 = 128
+	if !testing.Short() {
+		attempts *= 16
+	}
+	const parallel = 32
+
+	var sem = make(chan bool, parallel)
+
+	var (
+		writeSuccesses, readSuccesses int64 // atomic
+		writeErrnoSeen, readErrnoSeen sync.Map
+	)
+
+	for n := attempts; n > 0; n-- {
+		sem <- true
+		go func() {
+			defer func() { <-sem }()
+
+			time.Sleep(time.Duration(rand.Intn(100)) * time.Microsecond)
+			offset := rand.Intn(chunkWords)
+			chunk := buf[offset*8 : (offset+chunkWords)*8]
+			if err := WriteFile(path, chunk, 0666); err == nil {
+				atomic.AddInt64(&writeSuccesses, 1)
+			} else if robustio.IsEphemeralError(err) {
+				var (
+					errno syscall.Errno
+					dup   bool
+				)
+				if errors.As(err, &errno) {
+					_, dup = writeErrnoSeen.LoadOrStore(errno, true)
+				}
+				if !dup {
+					t.Logf("ephemeral error: %v", err)
+				}
+			} else {
+				t.Errorf("unexpected error: %v", err)
+			}
+
+			time.Sleep(time.Duration(rand.Intn(100)) * time.Microsecond)
+			data, err := ReadFile(path)
+			if err == nil {
+				atomic.AddInt64(&readSuccesses, 1)
+			} else if robustio.IsEphemeralError(err) {
+				var (
+					errno syscall.Errno
+					dup   bool
+				)
+				if errors.As(err, &errno) {
+					_, dup = readErrnoSeen.LoadOrStore(errno, true)
+				}
+				if !dup {
+					t.Logf("ephemeral error: %v", err)
+				}
+				return
+			} else {
+				t.Errorf("unexpected error: %v", err)
+				return
+			}
+
+			if len(data) != 8*chunkWords {
+				t.Errorf("read %d bytes, but each write is a %d-byte file", len(data), 8*chunkWords)
+				return
+			}
+
+			u := binary.LittleEndian.Uint64(data)
+			for i := 1; i < chunkWords; i++ {
+				next := binary.LittleEndian.Uint64(data[i*8:])
+				if next != u+1 {
+					t.Errorf("wrote sequential integers, but read integer out of sequence at offset %d", i)
+					return
+				}
+				u = next
+			}
+		}()
+	}
+
+	for n := parallel; n > 0; n-- {
+		sem <- true
+	}
+
+	var minWriteSuccesses int64 = attempts
+	if runtime.GOOS == "windows" {
+		// Windows produces frequent "Access is denied" errors under heavy rename load.
+		// As long as those are the only errors and *some* of the writes succeed, we're happy.
+		minWriteSuccesses = attempts / 4
+	}
+
+	if writeSuccesses < minWriteSuccesses {
+		t.Errorf("%d (of %d) writes succeeded; want ≥ %d", writeSuccesses, attempts, minWriteSuccesses)
+	} else {
+		t.Logf("%d (of %d) writes succeeded (ok: ≥ %d)", writeSuccesses, attempts, minWriteSuccesses)
+	}
+
+	var minReadSuccesses int64 = attempts
+
+	switch runtime.GOOS {
+	case "windows":
+		// Windows produces frequent "Access is denied" errors under heavy rename load.
+		// As long as those are the only errors and *some* of the reads succeed, we're happy.
+		minReadSuccesses = attempts / 4
+
+	case "darwin", "ios":
+		// The filesystem on certain versions of macOS (10.14) and iOS (affected
+		// versions TBD) occasionally fail with "no such file or directory" errors.
+		// See https://golang.org/issue/33041 and https://golang.org/issue/42066.
+		// The flake rate is fairly low, so ensure that at least 75% of attempts
+		// succeed.
+		minReadSuccesses = attempts - (attempts / 4)
+	}
+
+	if readSuccesses < minReadSuccesses {
+		t.Errorf("%d (of %d) reads succeeded; want ≥ %d", readSuccesses, attempts, minReadSuccesses)
+	} else {
+		t.Logf("%d (of %d) reads succeeded (ok: ≥ %d)", readSuccesses, attempts, minReadSuccesses)
+	}
+}