There's a problem with the session mutex and file handling in PHP that can cause deadlocks and php to fail @ maximum execution time.

This includes any kind of exec flavour, and also readfile. We had a problem where if the user tried to download a file from our server that was sent with readfile, but then cancelled and retried straight away, php would freeze and time out. The solution was to end_session() before sending the file, this fixed it.
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Server IP: 92.48.74.199
Probable Submitter: 80.6.91.225
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Manual Page -- http://www.php.net/manual/en/function.readfile.php
Edit        -- https://master.php.net/note/edit/86155
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Del: in docs     -- https://master.php.net/note/delete/86155/in+docs
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