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Date: Mon, 20 Oct 2014 21:03:50 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Threads
Message-ID: <20141020190350.GB32374@calimero.vinschen.de>
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References: <54450835 DOT 3050602 AT cornell DOT edu> <20141020164324 DOT GA32374 AT calimero DOT vinschen DOT de>
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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) short=
ly
> > after starting it, and I obtained the backtrace appended at the end of =
this
> > message.
> >=20
> > I assume Thread 12 was created by gdb.
> [...]
> > I don't
> > have any idea where the other threads came from.  Presumably at least o=
ne of
> > them was created by Glib.
> >=20
> > The situation is similar with emacs-w32 and emacs-nox, but with fewer t=
hreads.
> >=20
> > In general, is there a way I can understand where all the threads come =
from?
>=20
> There's no simple generic way to do that, afaik.
>=20
> 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.


HTH,
Corinna


(*)  http://msdn.microsoft.com/en-us/windows/hardware/hh852365.aspx
(**) http://msdn.microsoft.com/en-us/windows/hardware/gg463028.aspx

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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