lockedfile_test.go

     1  // Copyright 2018 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  // js and wasip1 do not support inter-process file locking.
     6  //
     7  //go:build !js && !wasip1
     8  
     9  package lockedfile_test
    10  
    11  import (
    12  	"fmt"
    13  	"internal/testenv"
    14  	"os"
    15  	"path/filepath"
    16  	"testing"
    17  	"time"
    18  
    19  	"cmd/go/internal/lockedfile"
    20  )
    21  
    22  const (
    23  	quiescent            = 10 * time.Millisecond
    24  	probablyStillBlocked = 10 * time.Second
    25  )
    26  
    27  func mustBlock(t *testing.T, desc string, f func()) (wait func(*testing.T)) {
    28  	t.Helper()
    29  
    30  	done := make(chan struct{})
    31  	go func() {
    32  		f()
    33  		close(done)
    34  	}()
    35  
    36  	timer := time.NewTimer(quiescent)
    37  	defer timer.Stop()
    38  	select {
    39  	case <-done:
    40  		t.Fatalf("%s unexpectedly did not block", desc)
    41  	case <-timer.C:
    42  	}
    43  
    44  	return func(t *testing.T) {
    45  		logTimer := time.NewTimer(quiescent)
    46  		defer logTimer.Stop()
    47  
    48  		select {
    49  		case <-logTimer.C:
    50  			// We expect the operation to have unblocked by now,
    51  			// but maybe it's just slow. Write to the test log
    52  			// in case the test times out, but don't fail it.
    53  			t.Helper()
    54  			t.Logf("%s is unexpectedly still blocked after %v", desc, quiescent)
    55  
    56  			// Wait for the operation to actually complete, no matter how long it
    57  			// takes. If the test has deadlocked, this will cause the test to time out
    58  			// and dump goroutines.
    59  			<-done
    60  
    61  		case <-done:
    62  		}
    63  	}
    64  }
    65  
    66  func TestMutexExcludes(t *testing.T) {
    67  	t.Parallel()
    68  
    69  	path := filepath.Join(t.TempDir(), "lock")
    70  	mu := lockedfile.MutexAt(path)
    71  	t.Logf("mu := MutexAt(_)")
    72  
    73  	unlock, err := mu.Lock()
    74  	if err != nil {
    75  		t.Fatalf("mu.Lock: %v", err)
    76  	}
    77  	t.Logf("unlock, _  := mu.Lock()")
    78  
    79  	mu2 := lockedfile.MutexAt(mu.Path)
    80  	t.Logf("mu2 := MutexAt(mu.Path)")
    81  
    82  	wait := mustBlock(t, "mu2.Lock()", func() {
    83  		unlock2, err := mu2.Lock()
    84  		if err != nil {
    85  			t.Errorf("mu2.Lock: %v", err)
    86  			return
    87  		}
    88  		t.Logf("unlock2, _ := mu2.Lock()")
    89  		t.Logf("unlock2()")
    90  		unlock2()
    91  	})
    92  
    93  	t.Logf("unlock()")
    94  	unlock()
    95  	wait(t)
    96  }
    97  
    98  func TestReadWaitsForLock(t *testing.T) {
    99  	t.Parallel()
   100  
   101  	path := filepath.Join(t.TempDir(), "timestamp.txt")
   102  	f, err := lockedfile.Create(path)
   103  	if err != nil {
   104  		t.Fatalf("Create: %v", err)
   105  	}
   106  	defer f.Close()
   107  
   108  	const (
   109  		part1 = "part 1\n"
   110  		part2 = "part 2\n"
   111  	)
   112  	_, err = f.WriteString(part1)
   113  	if err != nil {
   114  		t.Fatalf("WriteString: %v", err)
   115  	}
   116  	t.Logf("WriteString(%q) = <nil>", part1)
   117  
   118  	wait := mustBlock(t, "Read", func() {
   119  		b, err := lockedfile.Read(path)
   120  		if err != nil {
   121  			t.Errorf("Read: %v", err)
   122  			return
   123  		}
   124  
   125  		const want = part1 + part2
   126  		got := string(b)
   127  		if got == want {
   128  			t.Logf("Read(_) = %q", got)
   129  		} else {
   130  			t.Errorf("Read(_) = %q, _; want %q", got, want)
   131  		}
   132  	})
   133  
   134  	_, err = f.WriteString(part2)
   135  	if err != nil {
   136  		t.Errorf("WriteString: %v", err)
   137  	} else {
   138  		t.Logf("WriteString(%q) = <nil>", part2)
   139  	}
   140  	f.Close()
   141  
   142  	wait(t)
   143  }
   144  
   145  func TestCanLockExistingFile(t *testing.T) {
   146  	t.Parallel()
   147  
   148  	path := filepath.Join(t.TempDir(), "existing.txt")
   149  	if err := os.WriteFile(path, []byte("ok"), 0777); err != nil {
   150  		t.Fatalf("os.WriteFile: %v", err)
   151  	}
   152  
   153  	f, err := lockedfile.Edit(path)
   154  	if err != nil {
   155  		t.Fatalf("first Edit: %v", err)
   156  	}
   157  
   158  	wait := mustBlock(t, "Edit", func() {
   159  		other, err := lockedfile.Edit(path)
   160  		if err != nil {
   161  			t.Errorf("second Edit: %v", err)
   162  		}
   163  		other.Close()
   164  	})
   165  
   166  	f.Close()
   167  	wait(t)
   168  }
   169  
   170  // TestSpuriousEDEADLK verifies that the spurious EDEADLK reported in
   171  // https://golang.org/issue/32817 no longer occurs.
   172  func TestSpuriousEDEADLK(t *testing.T) {
   173  	// 	P.1 locks file A.
   174  	// 	Q.3 locks file B.
   175  	// 	Q.3 blocks on file A.
   176  	// 	P.2 blocks on file B. (Spurious EDEADLK occurs here.)
   177  	// 	P.1 unlocks file A.
   178  	// 	Q.3 unblocks and locks file A.
   179  	// 	Q.3 unlocks files A and B.
   180  	// 	P.2 unblocks and locks file B.
   181  	// 	P.2 unlocks file B.
   182  
   183  	testenv.MustHaveExec(t)
   184  
   185  	dirVar := t.Name() + "DIR"
   186  
   187  	if dir := os.Getenv(dirVar); dir != "" {
   188  		// Q.3 locks file B.
   189  		b, err := lockedfile.Edit(filepath.Join(dir, "B"))
   190  		if err != nil {
   191  			t.Fatal(err)
   192  		}
   193  		defer b.Close()
   194  
   195  		if err := os.WriteFile(filepath.Join(dir, "locked"), []byte("ok"), 0666); err != nil {
   196  			t.Fatal(err)
   197  		}
   198  
   199  		// Q.3 blocks on file A.
   200  		a, err := lockedfile.Edit(filepath.Join(dir, "A"))
   201  		// Q.3 unblocks and locks file A.
   202  		if err != nil {
   203  			t.Fatal(err)
   204  		}
   205  		defer a.Close()
   206  
   207  		// Q.3 unlocks files A and B.
   208  		return
   209  	}
   210  
   211  	dir := t.TempDir()
   212  
   213  	// P.1 locks file A.
   214  	a, err := lockedfile.Edit(filepath.Join(dir, "A"))
   215  	if err != nil {
   216  		t.Fatal(err)
   217  	}
   218  
   219  	cmd := testenv.Command(t, os.Args[0], "-test.run=^"+t.Name()+"$")
   220  	cmd.Env = append(os.Environ(), fmt.Sprintf("%s=%s", dirVar, dir))
   221  
   222  	qDone := make(chan struct{})
   223  	waitQ := mustBlock(t, "Edit A and B in subprocess", func() {
   224  		out, err := cmd.CombinedOutput()
   225  		if err != nil {
   226  			t.Errorf("%v:\n%s", err, out)
   227  		}
   228  		close(qDone)
   229  	})
   230  
   231  	// Wait until process Q has either failed or locked file B.
   232  	// Otherwise, P.2 might not block on file B as intended.
   233  locked:
   234  	for {
   235  		if _, err := os.Stat(filepath.Join(dir, "locked")); !os.IsNotExist(err) {
   236  			break locked
   237  		}
   238  		timer := time.NewTimer(1 * time.Millisecond)
   239  		select {
   240  		case <-qDone:
   241  			timer.Stop()
   242  			break locked
   243  		case <-timer.C:
   244  		}
   245  	}
   246  
   247  	waitP2 := mustBlock(t, "Edit B", func() {
   248  		// P.2 blocks on file B. (Spurious EDEADLK occurs here.)
   249  		b, err := lockedfile.Edit(filepath.Join(dir, "B"))
   250  		// P.2 unblocks and locks file B.
   251  		if err != nil {
   252  			t.Error(err)
   253  			return
   254  		}
   255  		// P.2 unlocks file B.
   256  		b.Close()
   257  	})
   258  
   259  	// P.1 unlocks file A.
   260  	a.Close()
   261  
   262  	waitQ(t)
   263  	waitP2(t)
   264  }
   265
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