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os/exec: add closeOnce.WriteString method

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Add an explicit WriteString method to closeOnce that acquires the
writers lock.  This overrides the one promoted from the
embedded *os.File field.  The promoted one naturally does not acquire
the lock, and can therefore race with the Close method.

Fixes #17647.

Change-Id: I3460f2a0d503449481cfb2fd4628b4855ab0ecdf
Reviewed-on: https://go-review.googlesource.com/33298
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Ian Lance Taylor 2016-11-15 17:55:28 -08:00
parent 1b66b38e25
commit b906df653b
3 changed files with 35 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
src/cmd/dist/test.go vendored
View File

@ -1055,7 +1055,7 @@ func (t *tester) runFlag(rx string) string {
func (t *tester) raceTest(dt *distTest) error {
t.addCmd(dt, "src", "go", "test", "-race", "-i", "runtime/race", "flag", "os/exec")
t.addCmd(dt, "src", "go", "test", "-race", t.runFlag("Output"), "runtime/race")
t.addCmd(dt, "src", "go", "test", "-race", "-short", t.runFlag("TestParse|TestEcho"), "flag", "os/exec")
t.addCmd(dt, "src", "go", "test", "-race", "-short", t.runFlag("TestParse|TestEcho|TestStdinCloseRace"), "flag", "os/exec")
// We don't want the following line, because it
// slows down all.bash (by 10 seconds on my laptop).
// The race builder should catch any error here, but doesn't.
@ -1068,7 +1068,7 @@ func (t *tester) raceTest(dt *distTest) error {
}
if t.extLink() {
// Test with external linking; see issue 9133.
t.addCmd(dt, "src", "go", "test", "-race", "-short", "-ldflags=-linkmode=external", t.runFlag("TestParse|TestEcho"), "flag", "os/exec")
t.addCmd(dt, "src", "go", "test", "-race", "-short", "-ldflags=-linkmode=external", t.runFlag("TestParse|TestEcho|TestStdinCloseRace"), "flag", "os/exec")
}
return nil
}

7
src/os/exec/exec.go
View File

@ -579,6 +579,13 @@ func (c *closeOnce) Write(b []byte) (int, error) {
return n, err
}
func (c *closeOnce) WriteString(s string) (int, error) {
c.writers.RLock()
n, err := c.File.WriteString(s)
c.writers.RUnlock()
return n, err
}
// StdoutPipe returns a pipe that will be connected to the command's
// standard output when the command starts.
//

26
src/os/exec/exec_test.go
View File

@ -246,6 +246,32 @@ func TestStdinClose(t *testing.T) {
check("Wait", cmd.Wait())
}
// Issue 17647.
func TestStdinCloseRace(t *testing.T) {
cmd := helperCommand(t, "stdinClose")
stdin, err := cmd.StdinPipe()
if err != nil {
t.Fatalf("StdinPipe: %v", err)
}
if err := cmd.Start(); err != nil {
t.Fatalf("Start: %v", err)
}
go func() {
if err := cmd.Process.Kill(); err != nil {
t.Errorf("Kill: %v", err)
}
}()
go func() {
io.Copy(stdin, strings.NewReader(stdinCloseTestString))
if err := stdin.Close(); err != nil {
t.Errorf("stdin.Close: %v", err)
}
}()
if err := cmd.Wait(); err == nil {
t.Fatalf("Wait: succeeded unexpectedly")
}
}
// Issue 5071
func TestPipeLookPathLeak(t *testing.T) {
fd0, lsof0 := numOpenFDS(t)