From owner-freebsd-current@FreeBSD.ORG Mon Sep 22 13:31:33 2014 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 2F4C7EE8; Mon, 22 Sep 2014 13:31:33 +0000 (UTC) Received: from mail.netplex.net (mail.netplex.net [204.213.176.9]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "*.netplex.net", Issuer "RapidSSL CA" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id DD8C48EA; Mon, 22 Sep 2014 13:31:32 +0000 (UTC) Received: from sea.ntplx.net (sea.ntplx.net [204.213.176.11]) by mail.netplex.net (8.14.9/8.14.9/NETPLEX) with ESMTP id s8MDJUqC018844; Mon, 22 Sep 2014 09:19:30 -0400 X-Virus-Scanned: by AMaViS and Clam AntiVirus (mail.netplex.net) X-Greylist: Message whitelisted by DRAC access database, not delayed by milter-greylist-4.4.3 (mail.netplex.net [204.213.176.9]); Mon, 22 Sep 2014 09:19:30 -0400 (EDT) Date: Mon, 22 Sep 2014 09:19:30 -0400 (EDT) From: Daniel Eischen X-X-Sender: eischen@sea.ntplx.net Reply-To: Daniel Eischen To: Julian Elischer Subject: Re: libthr and main thread stack size In-Reply-To: <541E31E0.8020108@freebsd.org> Message-ID: References: <53E36E84.4060806@ivan-labs.com> <20140916081324.GQ2737@kib.kiev.ua> <5242716.s4iaScq0Bu@ralph.baldwin.cx> <541E31E0.8020108@freebsd.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: Konstantin Belousov , "Ivan A. Kosarev" , freebsd-current@freebsd.org X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 22 Sep 2014 13:31:33 -0000 On Sun, 21 Sep 2014, Julian Elischer wrote: > On 9/20/14, 3:27 AM, John Baldwin wrote: >> On Tuesday, September 16, 2014 11:13:24 AM Konstantin Belousov wrote: >>> On Mon, Sep 15, 2014 at 03:47:41PM -0600, Justin T. Gibbs wrote: >>>> On Aug 8, 2014, at 5:22 AM, Konstantin Belousov >>>> wrote: >>>> >>>> ? >>>> >>>>> Below is the patch which adds environment variable >>>>> LIBPTHREAD_BIGSTACK_MAIN. Setting it to any value results in the >>>>> main thread stack left as is, and other threads allocate stack >>>>> below the area of RLIMIT_STACK. Try it. I do not want to set this >>>>> behaviour as default. >>>> Is there a reason this should not be the default? Looking at the >>>> getrlimit() page on the OpenGroup?s site they say: >>>> >>>> RLIMIT_STACK This is the maximum size of the initial thread's stack, >>>> in bytes. The implementation does not automatically grow the stack >>>> beyond this limit. If this limit is exceeded, SIGSEGV shall be >>>> generated for the thread. If the thread is blocking SIGSEGV, or the >>>> process is ignoring or catching SIGSEGV and has not made arrangements >>>> to use an alternate stack, the disposition of SIGSEGV shall be set to >>>> SIG_DFL before it is generated. >>>> >>>> Does posix say something different? >>>> >>>> I ran into this issue when debugging a segfault on Postgres when >>>> running an (arguably quite bogus) query that should have fit within >>>> both the configured stack rlimit and Postgres? configured stack limit. >>>> The Postgres backend is really just single threaded, but happens >>>> to pull in libpthread due to the threading support in some of the >>>> libraries it uses. The segfault definitely violates POLA. >>>> >>>> ? Justin >>> I am conservative to not disturb the address space layout in single go. >>> If enough people test this setting, I can consider flipping the default >>> to the reverse. >>> >>> I am still curious why the things were done in this way, but nobody >>> replied. >> I suspect it was done out of reasons of being overly conservative in >> interpreting RLIMIT_STACK. I think it is quite surprising behavior though >> and >> would rather we make your option the default and implement what the Open >> Group >> says above. >> > that is my memory.. > The transition from a non threaded app to a threaded app with one thread is > sort of an undefined area. > Feel free to change it if Dan agrees.. I'm all for adopting what POSIX specifies as the default. I would shy away from adding another knob (LIBPTHREAD_BIGSTACK_MAIN) if possible. -- DE