Drupal Cron Run Failing and Timing Out

So I was trying to manually run cron.php on a drupal site, and it was timing out because the cron job couldn't finish. The cron job is quite intense, and I'm sure it isn't finishing because I am trying to run it during the day on a busy site. So in order to tell Drupal to forget about your last cron attempt:

1. go into your drupal database
2. go into the 'variable' table
3. sort by the 'name' column ascending order
4. look for any variable names beginning with 'cron_' and delete them

Here are some MySQL queries that should get the job done:

select * from variable where name like 'cron%';
delete from variable where name like 'cron%';

Or if you're captain cool, you can use drush:

drush vdel cron_last
drush vdel cron_threshold_semaphore
drush vdel cron_safe_threshold

Also, check out this post to see which modules that implement hook_cron may be causing the failed cron run.

http://millwoodonline.co.uk/blog/drupal-cron-failing-not-sure-why-heres-handy-drush-command