exec: get the exit code from sync pipe instead of file

Before, we were getting the exit code from the file, in which we waited an arbitrary amount of time (5 seconds) for the file, and segfaulted if we didn't find it. instead, we should be a bit more certain conmon has sent the exit code. Luckily, it sends the exit code along the sync pipe fd, so we can read it from there

Adapt the ExecContainer interface to pass along a channel to get the pid and exit code from conmon, to be able to read both from the pipe

Signed-off-by: Peter Hunt <pehunt@redhat.com>

1 files changed, 17 insertions, 8 deletions

diff --git a/libpod/container_api.go b/libpod/container_api.go
index ee879b69d..37a05bb75 100644
--- a/libpod/container_api.go
+++ b/libpod/container_api.go
@@ -282,7 +282,16 @@ func (c *Container) Exec(tty, privileged bool, env map[string]string, cmd []stri
 	opts.Resize = resize
 	opts.DetachKeys = detachKeys
 
-	pid, attachChan, err := c.ociRuntime.ExecContainer(c, sessionID, opts)
+	pid := 0
+	pipeDataChan, attachChan, err := c.ociRuntime.ExecContainer(c, sessionID, opts)
+	// if pipeDataChan isn't nil, we should set the err
+	if pipeDataChan != nil {
+		pidData := <-pipeDataChan
+		if pidData.err != nil {
+			err = pidData.err
+		}
+		pid = pidData.data
+	}
 	if err != nil {
 		ec := define.ExecErrorCodeGeneric
 		// Conmon will pass a non-zero exit code from the runtime as a pid here.
@@ -318,18 +327,18 @@ func (c *Container) Exec(tty, privileged bool, env map[string]string, cmd []stri
 
 	lastErr := <-attachChan
 
-	exitCode, err := c.readExecExitCode(sessionID)
-	if err != nil {
+	exitCodeData := <-pipeDataChan
+	if exitCodeData.err != nil {
 		if lastErr != nil {
 			logrus.Errorf(lastErr.Error())
 		}
-		lastErr = err
+		lastErr = exitCodeData.err
 	}
-	if exitCode != 0 {
+	if exitCodeData.data != 0 {
 		if lastErr != nil {
 			logrus.Errorf(lastErr.Error())
 		}
-		lastErr = errors.Wrapf(define.ErrOCIRuntime, "non zero exit code: %d", exitCode)
+		lastErr = errors.Wrapf(define.ErrOCIRuntime, "non zero exit code: %d", exitCodeData.data)
 	}
 
 	// Lock again
@@ -340,7 +349,7 @@ func (c *Container) Exec(tty, privileged bool, env map[string]string, cmd []stri
 	// Sync the container again to pick up changes in state
 	if err := c.syncContainer(); err != nil {
 		logrus.Errorf("error syncing container %s state to remove exec session %s", c.ID(), sessionID)
-		return exitCode, lastErr
+		return exitCodeData.data, lastErr
 	}
 
 	// Remove the exec session from state
@@ -348,7 +357,7 @@ func (c *Container) Exec(tty, privileged bool, env map[string]string, cmd []stri
 	if err := c.save(); err != nil {
 		logrus.Errorf("Error removing exec session %s from container %s state: %v", sessionID, c.ID(), err)
 	}
-	return exitCode, lastErr
+	return exitCodeData.data, lastErr
 }
 
 // AttachStreams contains streams that will be attached to the container