<?php
// called when saving a post.

public function tl_save_post($post_id){

	// dont do this on auosave.
  if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
        return;

    // verify this came from the our screen and with proper authorization,
    // because save_post can be triggered at other times


		$post = get_post($post_id);

  	if (!isset($post->post_type) || 'my_post_type' != $post->post_type ) {
        return;
    }

		// unhook this function so it doesn't loop infinitely
		remove_action( 'save_post', 'tl_save_post, 100 );

		// do stuff that might trigger another Save

    /* stuff here */

    // put back the hook
    add_action( 'save_post', 'tl_save_post, 100 );
}

add_action( 'save_post', 'tl_save_post, 100 );