Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:84584
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain zend.com designates 209.85.220.177 as permitted sender)
MIME-Version: 1.0
Date: Thu, 12 Mar 2015 00:44:34 +0300
Message-ID: <CA+9eiLs9rd8bcQzoOQ8t465FYOfZvw2_HW=XS7OeofO+_qkOCg@mail.gmail.com>
To: Rasmus Lerdorf <rasmus@lerdorf.com>, Nikita Popov <nikita.ppv@gmail.com>, 
	Xinchen Hui <xinchen.h@zend.com>, Anatol Belski <ab@php.net>, PHP Internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=bcaec52be9bf4c298c05110a2c01
Subject: Safe execution timeout handling
From: dmitry@zend.com (Dmitry Stogov)

--bcaec52be9bf4c298c05110a2c01
Content-Type: text/plain; charset=UTF-8

Hi,

Unsafe "max_execution_time" and "Out of Memory" handling is a huge problem,
that often lead to crashes and SHM corruption.

The PoC solves the first problem.

https://github.com/php/php-src/pull/1173

Instead of throwing zend_error() from signal handler, now we just set
EG(vm_interrupt) and EG(timed_out) flags. PHP VM checks EG(vm_interrupt)
flag on each JMPx instruction (potential loop iteration) and then throws
the same zend_error() from VM context. This is safe, and we don't need to
wrap some critical code sections with
HANDLE_BLOCK_INTERRUPTIONS/HANDLE_UNBLOCK_INTERRUPTIONS anymore (we will
need them only in opcache). A small overhead of checking EG(vm_interrupt)
on jumps is counterbalanced by improvement from
HANDLE_BLOCK_INTERRUPTIONS/HANDLE_UNBLOCK_INTERRUPTIONS removal.

Unfortunately this approach doesn't support interruption of long-running
internal functions yet. It should be extended in some way. May be
additional timeout.

Improvement ideas are welcome...

Also, do we need "safe" handling for other signals?
I think no, but may be I miss something.

Thanks. Dmitry.

--bcaec52be9bf4c298c05110a2c01--