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Date: Thu, 21 Apr 2016 17:45:32 +0200
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To: Dmitry Stogov <dmitry@zend.com>
Cc: Nikita Popov <nikita.ppv@gmail.com>, Rasmus Lerdorf <rasmus@lerdorf.com>, Anatol Belski <ab@php.net>, 
	Antony Dovgal <antony.dovgal@gmail.com>, Zeev Suraski <zeev@zend.com>, Xinchen Hui <laruence@php.net>, 
	internals <internals@lists.php.net>
Content-Type: text/plain; charset=UTF-8
Subject: Re: [PHP-DEV] Safe timeout handling
From: jpauli@php.net (Julien Pauli)

On Wed, Apr 20, 2016 at 12:58 PM, Dmitry Stogov <dmitry@zend.com> wrote:
> Hi,
>
>
> It's a well known PHP problem, that exceeding of execution time-out (max_execution_time) may lead to unexpected crashes.
>
> They occur because PHP may be interrupted in inconsistent state, and attempt to release allocated by request resources leads to failure.
>
> Almost any big site sees these crashes from time to time.
>
>
> I propose to delay actual request termination until a "safe" point in interpreter.
>
> Signal handler will just set EG(timed_out) flag.
>
> Interpreter will check this time from time to time (on jumps and calls that may make loops or recursion) and perform the actual termination.
>
> This approach already works in PHP for Windows.
>
>
> In addition I introduce hard_timeout (default value 2 seconds).
>
> In case the "soft" timeout wasn't handled "safely" in that 2 seconds (because of long running internal function), PHP process will be terminated without attempt to free any resources.
>
> ZTS build will ignore "hard_timeout" (in the same way as PHP on Windows do).
>
>
> The PR: https://github.com/php/php-src/pull/1876
>
>
> It removes "exit_on_timeout" ini directive, and introduces "hard_timeout" instead.
>
> Additional checks in VM make 0.5-1% slowdown in term of instruction retired reported by callgrind.
>
> I think we don't need RFC for this. This is a long time desired fix.
>
>
> The same "interrupt" handling mechanism in the future may be reused for TICK and signal handling.
>
>
> Thanks. Dmitry.


Hi !

Good new.

No RFC needed, but that breaks ABI and could impact extensions.
So, 7.1 as target is OK, not 7.0


Julien.P