From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gdb-return-21300-listarch-gdb=sources.redhat.com@sources.redhat.com>
Received: (qmail 28131 invoked by alias); 27 Apr 2005 19:01:14 -0000
Mailing-List: contact gdb-help@sources.redhat.com; run by ezmlm
Precedence: bulk
List-Subscribe: <mailto:gdb-subscribe@sources.redhat.com>
List-Archive: <http://sources.redhat.com/ml/gdb/>
List-Post: <mailto:gdb@sources.redhat.com>
List-Help: <mailto:gdb-help@sources.redhat.com>, <http://sources.redhat.com/ml/#faqs>
Sender: gdb-owner@sources.redhat.com
Received: (qmail 28117 invoked from network); 27 Apr 2005 19:01:10 -0000
Received: from unknown (HELO nevyn.them.org) (66.93.172.17)
  by sourceware.org with SMTP; 27 Apr 2005 19:01:10 -0000
Received: from drow by nevyn.them.org with local (Exim 4.50 #1 (Debian))
	id 1DQrmX-0007aX-4Z; Wed, 27 Apr 2005 15:01:09 -0400
Date: Wed, 27 Apr 2005 22:46:00 -0000
From: Daniel Jacobowitz <drow@false.org>
To: David Lecomber <david@allinea.com>
Cc: gdb <gdb@sources.redhat.com>
Subject: Re: GDB locks up -- Cannot find new threads: generic error
Message-ID: <20050427190108.GA28978@nevyn.them.org>
Mail-Followup-To: David Lecomber <david@allinea.com>,
	gdb <gdb@sources.redhat.com>
References: <1114627357.31720.81.camel@cpc4-oxfd5-5-0-cust111.oxfd.cable.ntl.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1114627357.31720.81.camel@cpc4-oxfd5-5-0-cust111.oxfd.cable.ntl.com>
User-Agent: Mutt/1.5.8i
X-SW-Source: 2005-04/txt/msg00203.txt.bz2

On Wed, Apr 27, 2005 at 07:42:37PM +0100, David Lecomber wrote:
> (gdb) b main
> Breakpoint 1 at 0x804ed18: file
> main.cpp, line 10.
> (gdb) run
> Starting program: a.out
> warning: linux_test_for_tracefork: unexpected result from waitpid
> (28261,
> status 0x117f)
> [Thread debugging using libthread_db enabled]
> Error while reading shared library symbols:
> Cannot find new threads: generic error
> 
> at this point GDB does nothing and is unresponsive to any user input.  
> 
> The  system is:
> kernel-2.4.21-27.EL
> glibc-2.3.2-95.30

At a guess, your kernel is buggered.  You really should never see that
warning.  The unexpected signal is SIGCHLD; your kernel has accepted
the SETOPTIONS but obviously failed to stop when the test thread
vforked.

> - and if it helps,  I turned on debug of  lin-lwp and saw:
> 
> Starting program: ./a.out
> CW: waitpid 28606 received Trace/breakpoint trap (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Child exited (stopped)
> CW: waitpid 28606 received Trace/breakpoint trap (stopped)
> warning: linux_test_for_tracefork: unexpected result from waitpid
> (28629,
> status
> 0x117f)
> CW: waitpid 28606 received Trace/breakpoint trap (stopped)
> [Thread debugging using libthread_db enabled]
> Error while reading shared library symbols:
> Cannot find new threads: generic error
> LLR: PTRACE_SINGLESTEP process 28606, 0 (resume event thread)
> LLW: waitpid 28606 received Trace/breakpoint trap (stopped)

So um, if the program has stopped, what does GDB think it's still
waiting for?  Might want to strace gdb (without -f, with -e
wait4,ptrace).

-- 
Daniel Jacobowitz
CodeSourcery, LLC