From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <goswin-v-b@web.de>
X-Original-To: caml-list@yquem.inria.fr
Delivered-To: caml-list@yquem.inria.fr
Received: from mail4-relais-sop.national.inria.fr (mail4-relais-sop.national.inria.fr [192.134.164.105])
	by yquem.inria.fr (Postfix) with ESMTP id B32D9BBAF
	for <caml-list@yquem.inria.fr>; Thu, 25 Feb 2010 08:26:08 +0100 (CET)
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: AgwCABS1hUvZSMDqjWdsb2JhbACbFRUBAQEBCQkKCREFH7wThHMEhhc
X-IronPort-AV: E=Sophos;i="4.49,537,1262559600"; 
   d="scan'208";a="57767955"
Received: from fmmailgate03.web.de ([217.72.192.234])
  by mail4-smtp-sop.national.inria.fr with ESMTP; 25 Feb 2010 08:26:08 +0100
Received: from smtp06.web.de (fmsmtp06.dlan.cinetic.de [172.20.5.172])
	by fmmailgate03.web.de (Postfix) with ESMTP id D3B6B13FFB0A0;
	Thu, 25 Feb 2010 08:25:31 +0100 (CET)
Received: from [85.216.85.71] (helo=frosties.localdomain)
	by smtp06.web.de with asmtp (TLSv1:AES256-SHA:256)
	(WEB.DE 4.110 #314)
	id 1NkY6F-0002sz-00; Thu, 25 Feb 2010 08:25:31 +0100
Received: from mrvn by frosties.localdomain with local (Exim 4.71)
	(envelope-from <goswin-v-b@web.de>)
	id 1NkY6E-00036R-Td; Thu, 25 Feb 2010 08:25:31 +0100
From: Goswin von Brederlow <goswin-v-b@web.de>
To: Philippe Wang <philippe.wang.lists@gmail.com>
Cc: Goswin von Brederlow <goswin-v-b@web.de>,
	caml-list <caml-list@inria.fr>
Subject: Re: [Caml-list] Question about ocaml threads and TLS (on linux)
References: <87ocje2vtv.fsf@frosties.localdomain>
	<4d1b2df21002241322l63b82636hf7465ec05de9d8ed@mail.gmail.com>
Date: Thu, 25 Feb 2010 08:25:30 +0100
In-Reply-To: <4d1b2df21002241322l63b82636hf7465ec05de9d8ed@mail.gmail.com>
	(Philippe Wang's message of "Wed, 24 Feb 2010 22:22:06 +0100")
Message-ID: <87635l4w0l.fsf@frosties.localdomain>
User-Agent: Gnus/5.110009 (No Gnus v0.9) XEmacs/21.4.22 (linux, no MULE)
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Sender: goswin-v-b@web.de
X-Sender: goswin-v-b@web.de
X-Provags-ID: V01U2FsdGVkX1/BMRoPmtTc7FAHuTkNSZE0J3fBs6JiHLinc6AP
	Yn3m3IEA5yfVRfvZ1PCsUTQu+HHLRuq8lMt5BUh88eH89UzVwL
	UbEjS0OUY=
X-Spam: no; 0.00; ocaml:01 ocaml:01 compiler:01 ocamlopt:01 stub:01 stub:01 bytecode:01 ocaml's:01 runtime:01 compiler:01 pointer:01 buf:01 cheers:01 mfg:98 threads:01 

Philippe Wang <philippe.wang.lists@gmail.com> writes:

> Hi,
>
> I'm not sure I understand (though I've read the whole text), but maybe
> this will answer your question:
> On Linux, OCaml threads (with the native compiler "ocamlopt") are
> implemented with POSIX threads (in C), so when your OCaml thread runs
> the C stub, it's the same as if you were running the C stub in some C
> thread.

How about bytecode?

> When you are in a section declared as a blocking section, a collection
> can be triggered concurrently in another thread and so the heap must
> not be accessed neither for reading or writing, that's all.
>
> Using __thread recent feature should also work if you manage to
> compile everything correctly. Notably, we use it in some places in
> ocaml4multicore (a patch to ocaml's runtime library to allow parallel
> threads). However, I don't know how __thread is handled by the
> compiler... I mean : it there a pointer for buf in every thread or
> only in those that use it?

Only in those that use it. But that will be multiple threads. In those
that don't use it 4/8 bytes will be wasted.

> I hope my answer isn't useless!
>
> Cheers,

MfG
        Goswin