My error_log is full of deadlock error messages caused when the cron row in my wp_options table is updated by something. The update statement is always the same, but seems to be called at irregular time intervals. I've disabled wp-cron through wp-config.php and it is not set to run in crontab. As stipulated, the intervals with which the error messages occur appear to be on page loads, that is, they are irregular but frequent (every few minutes). I've looked at the cron API and think I can see what is being called ( wp_schedule_event() function) but I've no idea why it should be called if wp-cron has been disabled.