diff --git a/libcontainer/container_linux.go b/libcontainer/container_linux.go index 32854f43..06aee059 100644 --- a/libcontainer/container_linux.go +++ b/libcontainer/container_linux.go @@ -5,6 +5,7 @@ package libcontainer import ( "bytes" "encoding/json" + "errors" "fmt" "io" "io/ioutil" @@ -267,20 +268,70 @@ func (c *linuxContainer) Exec() error { func (c *linuxContainer) exec() error { path := filepath.Join(c.root, execFifoFilename) - f, err := os.OpenFile(path, os.O_RDONLY, 0) - if err != nil { - return newSystemErrorWithCause(err, "open exec fifo for reading") + + fifoOpen := make(chan struct{}) + select { + case <-awaitProcessExit(c.initProcess.pid(), fifoOpen): + return errors.New("container process is already dead") + case result := <-awaitFifoOpen(path): + close(fifoOpen) + if result.err != nil { + return result.err + } + f := result.file + defer f.Close() + if err := readFromExecFifo(f); err != nil { + return err + } + return os.Remove(path) } - defer f.Close() - data, err := ioutil.ReadAll(f) +} + +func readFromExecFifo(execFifo io.Reader) error { + data, err := ioutil.ReadAll(execFifo) if err != nil { return err } - if len(data) > 0 { - os.Remove(path) - return nil + if len(data) <= 0 { + return fmt.Errorf("cannot start an already running container") } - return fmt.Errorf("cannot start an already running container") + return nil +} + +func awaitProcessExit(pid int, exit <-chan struct{}) <-chan struct{} { + isDead := make(chan struct{}) + go func() { + for { + select { + case <-exit: + return + case <-time.After(time.Millisecond * 100): + stat, err := system.Stat(pid) + if err != nil || stat.State == system.Zombie { + close(isDead) + return + } + } + } + }() + return isDead +} + +func awaitFifoOpen(path string) <-chan openResult { + fifoOpened := make(chan openResult) + go func() { + f, err := os.OpenFile(path, os.O_RDONLY, 0) + if err != nil { + fifoOpened <- openResult{err: newSystemErrorWithCause(err, "open exec fifo for reading")} + } + fifoOpened <- openResult{file: f} + }() + return fifoOpened +} + +type openResult struct { + file *os.File + err error } func (c *linuxContainer) start(process *Process, isInit bool) error {