X-Recipient: archive-cygwin AT delorie DOT com
DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:message-id:date:from:mime-version:to:subject
	:references:in-reply-to:content-type:content-transfer-encoding;
	 q=dns; s=default; b=yd2QFAL6Rg+RTP0f1Z7HiVtaMYyyz7gx6949c13pWf2
	4WK5AQqhIDEQt3uZuPJSq/JsKbP64vjhZsEaHC+nP1wHhsJmbhlJPnuSkIhuab0d
	evUcN4ORYT76u618zhf6x/ofeedSn7yKuBQ+i4wv+YLt1ymtoqbXb5CASXjBXx9g
	=
DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:message-id:date:from:mime-version:to:subject
	:references:in-reply-to:content-type:content-transfer-encoding;
	 s=default; bh=pZ7Sz3GMsqN+P5vVJV3sS4eVhps=; b=gVl/0D8dCwhgrdaLH
	fUrJ+oAicPo4YFUfxGt64KbUmmfL528lmlD2y5pEcWmnrI+LBufGybQu58d6LAUt
	8AQ5+VHGZ3+URkprR6D++/qrCdfIYk82dWsKRJ9ZM2mxy6yv2vFw6U4t012oIKOw
	lTSuPXOB+Zu59dSzrJCXMGDu3w=
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id: <cygwin.cygwin.com>
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com
Authentication-Results: sourceware.org; auth=none
X-Virus-Found: No
X-Spam-SWARE-Status: No, score=-2.7 required=5.0 tests=AWL,BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.2
X-HELO: limerock03.mail.cornell.edu
X-CornellRouted: This message has been Routed already.
Message-ID: <54456964.4090007@cornell.edu>
Date: Mon, 20 Oct 2014 15:58:28 -0400
From: Ken Brown <kbrown AT cornell DOT edu>
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0
MIME-Version: 1.0
To: cygwin AT cygwin DOT com
Subject: Re: Threads
References: <54450835 DOT 3050602 AT cornell DOT edu> <20141020164324 DOT GA32374 AT calimero DOT vinschen DOT de> <20141020190350 DOT GB32374 AT calimero DOT vinschen DOT de>
In-Reply-To: <20141020190350.GB32374@calimero.vinschen.de>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
X-IsSubscribed: yes

On 10/20/2014 3:03 PM, Corinna Vinschen wrote:
> On Oct 20 18:43, Corinna Vinschen wrote:
>> On Oct 20 09:03, Ken Brown wrote:
>>> When trying to debug emacs in gdb, I see several threads, but it's not
>>> always clear who created those threads and what they're doing.  As an
>>> example, I attached gdb to an emacs-X11 process (running under X) shortly
>>> after starting it, and I obtained the backtrace appended at the end of this
>>> message.
>>>
>>> I assume Thread 12 was created by gdb.
>> [...]
>>> I don't
>>> have any idea where the other threads came from.  Presumably at least one of
>>> them was created by Glib.
>>>
>>> The situation is similar with emacs-w32 and emacs-nox, but with fewer threads.
>>>
>>> In general, is there a way I can understand where all the threads come from?
>>
>> There's no simple generic way to do that, afaik.
>>
>> One big problem is to have all the symbols.  You should definitely
>> install the debuginfo packages of all potentially affected packages, not
>> only cygwin-debuginfo.  If you want to find out where threads are called
>> from the application, you might get a clue by running emacs under GDB and
>> set a breakpoint to pthread_create.
>
> Btw., I don't know if that helps, but the function names of native
> Windows functions given in the GDB backtrace may be off because GDB
> doesn't have access to the Windows DLL symbol tables.  If you want to
> analyze the stacks from that side, you should install WinDbg(*) and the
> symbol files for your OS(**).  If you start the process from WinDbg, you
> can better see the Windows functions called from these threads, while
> not getting any info about the functions from inside the application
> or the Cygwin DLLs.

Thanks, I'll give that a try.

> One of the headaches when porting is sometimes the ABI.  While on Linux
> the first 6 arguments to a function are given in registers, on Windows
> only 4 args are in registers.  This can result in bugs when calling
> functions with more than 4 parameters, which are invisible on Linux, due
> to the way 32 bit parameter are stored in registers on x86_64.  This
> happened to us already for at least one package.

Am I right in thinking this can only be an issue if the source includes 
assembler code?

Ken

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple