RE: GDB support

One other detail. With the TCore kernel patch all of the threads in a kernel
clone thread group are dumped into a single core file that works with gdb 
and the existing Linuxthreads support, providing a browse only environment 
to view the active threads and their state at the time of the dump.

The TCore patch has been jointly developed by several teams, with Intel and 
IBM participating. It refines earlier approaches by generating a single core
file instead of 1 per thread, attempts to stop the active threads quickly 
to improve the accuracy of the snapshot, and dumps in a standard way that is
compliant to the ELF core dumping and the current implementation of gdb. A 
version is available for the 2.4.17 kernel and for the 2.5/RH 7.3 kernel
that
uses the O1 scheduler. A IA32 version has been sent to the LKML, and a IA64 
version was also submitted and spawned discussions, see the mail threads.
The
IA32 version is in the CGL TLT 1.1 kernel.

This is marginally useful today for NGPT as the active threads are the
native processes, but I have found it useful for debugging several ngpt 
runtime problems. When the other gdb work is done it will allow per thread
debugging as it does for Linuxthreads.

Mark Gross or myself can provide the patches if you need to get them. The
LKML
should also have Mark's patch submissions and updates.

Thanks,
Dave Howell  


-----Original Message-----
From: Howell, David P 
Sent: Thursday, May 30, 2002 2:11 PM
To: 'Bill Abt'; Stephen Hemminger
Cc: [email protected]; Smith, Stanley W
Subject: RE: [pthreads-devel] GDB support


The implementation involves changes to the libthread_db to properly access 
the structures exported by the ngpt runtime, changes to the ngpt runtime 
to add manager thread capabilities for delivering thread events and for the
servicing of libthread_db requests, and it appears minimal changes to gdb
due to some dependence on the 1-1 thread model used for the Linuxthreads 
implementation in thread-db.c and lin-lwp.c.

The implementation closely follows the Solaris libthread_db architecture, 
and for this cut aims to provide the support features that are in the
standard
Linux offerings for Linuxthreads. This includes thread discovery, thread 
context debugging, and minimal thread events (create, destroy, etc). Future 
updates will add lock/mutex events and object manipulation. 

The plan is to provide the debug support as part of the ngpt runtime, and
add
a libthread_db runtime as the interface between gdb and the ngpt runtime. I 
have the libthread_db source and build as a subdirectory of the standard
source
tarball directory build. It will be managed using configure as the rest of
the
ngpt code and feature selections are.

The gdb portion is still a bit up in the air, not sure how best to deliver
it
short term but longer term the plan would be to contribute it back into the
gdb
source tarball and have it enabled by it's configure scripts. We can
temporarily
make it part of the NGPT tarball until it's acceptance into the gdb code
base.
 
The code is in debug now and is planned for submission for ngpt-1.9.3.

Thanks,
Dave Howell

-----Original Message-----
From: Bill Abt [mailto:[email protected]]
Sent: Wednesday, May 29, 2002 6:49 PM
To: Stephen Hemminger
Cc: [email protected]
Subject: Re: [pthreads-devel] GDB support


On 05/29/2002 at 03:09:19 PM MST, Stephen Hemminger <[email protected]>
wrote:

>
> Is anyone actively working on better GDB support of NGPT threads.
> It shouldn't be too hard since GDB already works on other operating
> systems that support N:M thread model. The problem is probably harder if
> you have to deal with dynamic detection of both forms of linux thread
> libraries.
>

GDB support is currently planned for release for NGPT 2.0.  NGPT 1.9.3 will
probably contain the first release of this support.  We're doing it via the
thread_db libraries.


Regards,
     Bill Abt
     Senior Software Engineer
     Next Generation POSIX Threading for Linux
     IBM Cambridge, MA, USA 02142
     Ext: +(00)1 603-673-3440 or +(00)1 617-693-1591
     T/L: 253-9938 (Normal)
     T/L: 693-1591 (Backup)
     Cell: +(00)1 617-803-7514
     [email protected] or [email protected]
     http://oss.software.ibm.com/developerworks/opensource/pthreads

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