Merge pull request #2185 from liggitt/exec-race
Fix race checking for process exit and waiting for exec fifo
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commit
a88592a634
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@ -265,22 +265,24 @@ func (c *linuxContainer) Exec() error {
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func (c *linuxContainer) exec() error {
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path := filepath.Join(c.root, execFifoFilename)
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fifoOpen := make(chan struct{})
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pid := c.initProcess.pid()
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blockingFifoOpenCh := awaitFifoOpen(path)
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for {
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select {
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case <-awaitProcessExit(c.initProcess.pid(), fifoOpen):
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case result := <-blockingFifoOpenCh:
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return handleFifoResult(result)
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case <-time.After(time.Millisecond * 100):
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stat, err := system.Stat(pid)
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if err != nil || stat.State == system.Zombie {
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// could be because process started, ran, and completed between our 100ms timeout and our system.Stat() check.
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// see if the fifo exists and has data (with a non-blocking open, which will succeed if the writing process is complete).
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if err := handleFifoResult(fifoOpen(path, false)); err != nil {
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return errors.New("container process is already dead")
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case result := <-awaitFifoOpen(path):
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close(fifoOpen)
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if result.err != nil {
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return result.err
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}
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f := result.file
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defer f.Close()
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if err := readFromExecFifo(f); err != nil {
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return err
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return nil
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}
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}
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return os.Remove(path)
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}
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}
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@ -295,38 +297,39 @@ func readFromExecFifo(execFifo io.Reader) error {
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return nil
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}
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func awaitProcessExit(pid int, exit <-chan struct{}) <-chan struct{} {
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isDead := make(chan struct{})
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go func() {
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for {
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select {
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case <-exit:
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return
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case <-time.After(time.Millisecond * 100):
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stat, err := system.Stat(pid)
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if err != nil || stat.State == system.Zombie {
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close(isDead)
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return
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}
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}
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}
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}()
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return isDead
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}
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func awaitFifoOpen(path string) <-chan openResult {
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fifoOpened := make(chan openResult)
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go func() {
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f, err := os.OpenFile(path, os.O_RDONLY, 0)
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if err != nil {
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fifoOpened <- openResult{err: newSystemErrorWithCause(err, "open exec fifo for reading")}
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return
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}
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fifoOpened <- openResult{file: f}
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result := fifoOpen(path, true)
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fifoOpened <- result
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}()
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return fifoOpened
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}
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func fifoOpen(path string, block bool) openResult {
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flags := os.O_RDONLY
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if !block {
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flags |= syscall.O_NONBLOCK
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}
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f, err := os.OpenFile(path, flags, 0)
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if err != nil {
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return openResult{err: newSystemErrorWithCause(err, "open exec fifo for reading")}
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}
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return openResult{file: f}
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}
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func handleFifoResult(result openResult) error {
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if result.err != nil {
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return result.err
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}
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f := result.file
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defer f.Close()
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if err := readFromExecFifo(f); err != nil {
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return err
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}
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return os.Remove(f.Name())
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}
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type openResult struct {
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file *os.File
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err error
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@ -218,13 +218,17 @@ function wait_for_container() {
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local attempts=$1
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local delay=$2
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local cid=$3
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# optionally wait for a specific status
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local wait_for_status="${4:-}"
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local i
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for ((i = 0; i < attempts; i++)); do
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runc state $cid
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if [[ "$status" -eq 0 ]]; then
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if [[ "${output}" == *"${wait_for_status}"* ]]; then
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return 0
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fi
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fi
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sleep $delay
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done
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@ -237,13 +241,17 @@ function wait_for_container_inroot() {
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local attempts=$1
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local delay=$2
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local cid=$3
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# optionally wait for a specific status
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local wait_for_status="${4:-}"
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local i
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for ((i = 0; i < attempts; i++)); do
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ROOT=$4 runc state $cid
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if [[ "$status" -eq 0 ]]; then
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if [[ "${output}" == *"${wait_for_status}"* ]]; then
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return 0
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fi
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fi
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sleep $delay
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done
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@ -205,7 +205,7 @@ EOF
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__runc run test_busybox
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) &
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wait_for_container 15 1 test_busybox
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wait_for_container 15 1 test_busybox running
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testcontainer test_busybox running
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# Kill the container.
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