debugging gdb using gdb

debugging gdb using gdb

[paawan oza]

Hi,

during reversible implementation, I am trying to debug arm-gdb using arm-gdb.
so i connect through telnet terminal and open two different terminals.
and run both the gdb on target and attach the one gdb with another one.
the moment I attach another gdb and give continue command, the gdb being 
debugged, looses iis terminal, and I am not able to type anything, and gdb does 
not accept any keyboard input and it hangs.

Regards,
Oza.



      

Re: debugging gdb using gdb

[Michael Snyder]

paawan oza wrote:
> Hi,
> 
> during reversible implementation, I am trying to debug arm-gdb using arm-gdb.
> so i connect through telnet terminal and open two different terminals.
> and run both the gdb on target and attach the one gdb with another one.
> the moment I attach another gdb and give continue command, the gdb being 
> debugged, looses iis terminal, and I am not able to type anything, and gdb does 
> not accept any keyboard input and it hangs.
> 
> Regards,
> Oza.

What happens if you try the same thing on x86 linux?

Re: debugging gdb using gdb

[paawan oza]

it works absolutely fine on x86 linux.
on both terminals gdb allows input output at any time.


the difference is;
in arm-linux I connect through telnet
while in x86-linux, just local native terminal.

Regards,
Oza.


----- Original Message ----
From: Michael Snyder <msnyder@vmware.com>
To: paawan oza <paawan1982@yahoo.com>
Cc: "gdb@sourceware.org" <gdb@sourceware.org>
Sent: Wed, February 16, 2011 11:38:25 PM
Subject: Re: debugging gdb using gdb

paawan oza wrote:
> Hi,
> 
> during reversible implementation, I am trying to debug arm-gdb using arm-gdb.
> so i connect through telnet terminal and open two different terminals.
> and run both the gdb on target and attach the one gdb with another one.
> the moment I attach another gdb and give continue command, the gdb being 
>debugged, looses iis terminal, and I am not able to type anything, and gdb does 
>not accept any keyboard input and it hangs.
> 
> Regards,
> Oza.

What happens if you try the same thing on x86 linux?


      

Re: debugging gdb using gdb

[Jan Kratochvil]

On Wed, 16 Feb 2011 04:41:59 +0100, paawan oza wrote:
> during reversible implementation, I am trying to debug arm-gdb using arm-gdb.
> so i connect through telnet terminal and open two different terminals.
> and run both the gdb on target and attach the one gdb with another one.
> the moment I attach another gdb and give continue command, the gdb being 
> debugged, looses iis terminal, and I am not able to type anything, and gdb does 
> not accept any keyboard input and it hangs.

One of the possibilities is a ptrace kernel bug.  For example there was a bug
reproducing only during gdb debugging of gdb (but not via attach):
	http://sources.redhat.com/cgi-bin/cvsweb.cgi/~checkout~/tests/ptrace-tests/tests/o_tracevfork-parent.c?cvsroot=systemtap

There are large parts of the ptrace implementation arch-dependent.  You can
compare the testsuite results on x86 vs. arm, although the bug you hit there
is most probably not yet convered by it:
	cvs -d :pserver:anoncvs:anoncvs@sourceware.org:/cvs/systemtap co ptrace-tests 

You can strace (without -f!) the second gdb to see how the ptrace/wait
syscalls behave.  Then you can try to minimize the behavior to a testcase for
an arm kernel fix.

(Sure the reason can be also completely different than ptrace.)


Regards,
Jan

Re: debugging gdb using gdb

[paawan oza]

can I get some inputs regarding following mail chain ?
as debugging gdb using gdb on arm is becoming difficult. 

Regards,
Oza.


----- Original Message ----
From: paawan oza <paawan1982@yahoo.com>
To: Michael Snyder <msnyder@vmware.com>
Cc: "gdb@sourceware.org" <gdb@sourceware.org>
Sent: Thu, February 17, 2011 9:01:12 AM
Subject: Re: debugging gdb using gdb

it works absolutely fine on x86 linux.
on both terminals gdb allows input output at any time.


the difference is;
in arm-linux I connect through telnet
while in x86-linux, just local native terminal.

Regards,
Oza.


----- Original Message ----
From: Michael Snyder <msnyder@vmware.com>
To: paawan oza <paawan1982@yahoo.com>
Cc: "gdb@sourceware.org" <gdb@sourceware.org>
Sent: Wed, February 16, 2011 11:38:25 PM
Subject: Re: debugging gdb using gdb

paawan oza wrote:
> Hi,
> 
> during reversible implementation, I am trying to debug arm-gdb using arm-gdb.
> so i connect through telnet terminal and open two different terminals.
> and run both the gdb on target and attach the one gdb with another one.
> the moment I attach another gdb and give continue command, the gdb being 
>debugged, looses iis terminal, and I am not able to type anything, and gdb does 

>not accept any keyboard input and it hangs.
> 
> Regards,
> Oza.

What happens if you try the same thing on x86 linux?


      

Re: debugging gdb using gdb

[Michael Snyder]

What happens if you do *exactly* the same thing on x86 linux?

paawan oza wrote:
> can I get some inputs regarding following mail chain ?
> as debugging gdb using gdb on arm is becoming difficult. 
> 
> Regards,
> Oza.
> 
> 
> ----- Original Message ----
> From: paawan oza <paawan1982@yahoo.com>
> To: Michael Snyder <msnyder@vmware.com>
> Cc: "gdb@sourceware.org" <gdb@sourceware.org>
> Sent: Thu, February 17, 2011 9:01:12 AM
> Subject: Re: debugging gdb using gdb
> 
> it works absolutely fine on x86 linux.
> on both terminals gdb allows input output at any time.
> 
> 
> the difference is;
> in arm-linux I connect through telnet
> while in x86-linux, just local native terminal.
> 
> Regards,
> Oza.
> 
> 
> ----- Original Message ----
> From: Michael Snyder <msnyder@vmware.com>
> To: paawan oza <paawan1982@yahoo.com>
> Cc: "gdb@sourceware.org" <gdb@sourceware.org>
> Sent: Wed, February 16, 2011 11:38:25 PM
> Subject: Re: debugging gdb using gdb
> 
> paawan oza wrote:
>> Hi,
>>
>> during reversible implementation, I am trying to debug arm-gdb using arm-gdb.
>> so i connect through telnet terminal and open two different terminals.
>> and run both the gdb on target and attach the one gdb with another one.
>> the moment I attach another gdb and give continue command, the gdb being 
>> debugged, looses iis terminal, and I am not able to type anything, and gdb does 
> 
>> not accept any keyboard input and it hangs.
>>
>> Regards,
>> Oza.
> 
> What happens if you try the same thing on x86 linux?
> 
> 
>       

Re: debugging gdb using gdb

[paawan oza]

Hi,

following is the scenerio.

x8-linux -> telnet sessions -> attaching gdb to gdb -> works fine
unix -> telnet sessions -> attaching gdb to gdb -> works fine
arm-linux -> telnet sessions -> attaching gdb to gdb -> gdb being debuged losses 
i/o cpability and it goes into infinite wait.

Regards,
Oza.



----- Original Message ----
From: Michael Snyder <msnyder@vmware.com>
To: paawan oza <paawan1982@yahoo.com>
Cc: "gdb@sourceware.org" <gdb@sourceware.org>
Sent: Sun, February 20, 2011 3:59:50 AM
Subject: Re: debugging gdb using gdb

What happens if you do *exactly* the same thing on x86 linux?

paawan oza wrote:
> can I get some inputs regarding following mail chain ?
> as debugging gdb using gdb on arm is becoming difficult. 
> Regards,
> Oza.
> 
> 
> ----- Original Message ----
> From: paawan oza <paawan1982@yahoo.com>
> To: Michael Snyder <msnyder@vmware.com>
> Cc: "gdb@sourceware.org" <gdb@sourceware.org>
> Sent: Thu, February 17, 2011 9:01:12 AM
> Subject: Re: debugging gdb using gdb
> 
> it works absolutely fine on x86 linux.
> on both terminals gdb allows input output at any time.
> 
> 
> the difference is;
> in arm-linux I connect through telnet
> while in x86-linux, just local native terminal.
> 
> Regards,
> Oza.
> 
> 
> ----- Original Message ----
> From: Michael Snyder <msnyder@vmware.com>
> To: paawan oza <paawan1982@yahoo.com>
> Cc: "gdb@sourceware.org" <gdb@sourceware.org>
> Sent: Wed, February 16, 2011 11:38:25 PM
> Subject: Re: debugging gdb using gdb
> 
> paawan oza wrote:
>> Hi,
>> 
>> during reversible implementation, I am trying to debug arm-gdb using arm-gdb.
>> so i connect through telnet terminal and open two different terminals.
>> and run both the gdb on target and attach the one gdb with another one.
>> the moment I attach another gdb and give continue command, the gdb being 
>>debugged, looses iis terminal, and I am not able to type anything, and gdb does 
>>
> 
>> not accept any keyboard input and it hangs.
>> 
>> Regards,
>> Oza.
> 
> What happens if you try the same thing on x86 linux?
> 
> 
>