Sorry, I did not check the actual code, just wrote my previous reply according to my memories. Now I had time to check it deeper. You have to add $isShellDisabled = true; before the try { around line 50, otherwise it will be overwritten.
What it does is that it disable the sh call between line 62-69:
} else if (!$isShellDisabled) {
$fileName = escapeshellarg(basename(__FILE__));
$cronPath = escapeshellarg(dirname(__FILE__) . '/cron.sh');
shell_exec(escapeshellcmd("/bin/sh $cronPath $fileName -mdefault 1 > /dev/null 2>&1 &"));
shell_exec(escapeshellcmd("/bin/sh $cronPath $fileName -malways 1 > /dev/null 2>&1 &"));
exit;
}The problem with our cron.sh call was that sh was that it was available and working indeed, but it called back the cron.php again, and here you go, an infinite loop.
Actually as I have checked the code once again, it looks like this part can be reached when there is no -m command line parameter when calling the cron.php. Honestly, I have never seen any tutorial mentioning that it is necessary, but after reading this reply, it makes some sense:
http://magento.stackexchange.com/questions/63707/which-cron-script-is-best-to-run-cron-php-or-cron-s...
So according to this solution you should use a similar cron job:
*/5 * * * * www-data /bin/sh /path/to/magento/cron.sh cron.php -m=default
*/5 * * * * www-data /bin/sh /path/to/magento/cron.sh cron.php -m=always
(www-data is your username and you may not have to use it, also sh location might differ)
Anyway, a fallback mode would be great for this case, when the admin don't set up the -m parameter.
