libpod: Factor out the call to PidFdOpen from (*Container).WaitForExit

libpod/container_api.go

@@ -516,21 +516,11 @@ func (c *Container) WaitForExit(ctx context.Context, pollInterval time.Duration)
 	var conmonTimer time.Timer
 	conmonTimerSet := false
 
-	conmonPidFd := -1
-	conmonPidFdTriggered := false
-
-	if c.state.ConmonPID != 0 {
-		// Track lifetime of conmon precisely using pidfd_open + poll.
-		// There are many cases for this to fail, for instance conmon is dead
-		// or pidfd_open is not supported (pre linux 5.3), so fall back to the
-		// traditional loop with poll + sleep
-		if fd, err := unix.PidfdOpen(c.state.ConmonPID, 0); err == nil {
-			conmonPidFd = fd
-			defer unix.Close(conmonPidFd)
-		} else if err != unix.ENOSYS && err != unix.ESRCH {
-			logrus.Debugf("PidfdOpen(%d) failed: %v", c.state.ConmonPID, err)
-		}
+	conmonPidFd := c.getConmonPidFd()
+	if conmonPidFd != -1 {
+		defer unix.Close(conmonPidFd)
 	}
+	conmonPidFdTriggered := false
 
 	getExitCode := func() (bool, int32, error) {
 		containerRemoved := false

libpod/container_internal_freebsd.go

@@ -272,3 +272,10 @@ func setVolumeAtime(mountPoint string, st os.FileInfo) error {
 func (c *Container) makePlatformBindMounts() error {
 	return nil
 }
+
+func (c *Container) getConmonPidFd() int {
+	// Note: kqueue(2) could be used here but that would require
+	// factoring out the call to unix.PollFd from WaitForExit so
+	// keeping things simple for now.
+	return -1
+}

libpod/container_internal_linux.go

@@ -665,3 +665,18 @@ func (c *Container) makePlatformBindMounts() error {
 	}
 	return nil
 }
+
+func (c *Container) getConmonPidFd() int {
+	if c.state.ConmonPID != 0 {
+		// Track lifetime of conmon precisely using pidfd_open + poll.
+		// There are many cases for this to fail, for instance conmon is dead
+		// or pidfd_open is not supported (pre linux 5.3), so fall back to the
+		// traditional loop with poll + sleep
+		if fd, err := unix.PidfdOpen(c.state.ConmonPID, 0); err == nil {
+			return fd
+		} else if err != unix.ENOSYS && err != unix.ESRCH {
+			logrus.Debugf("PidfdOpen(%d) failed: %v", c.state.ConmonPID, err)
+		}
+	}
+	return -1
+}