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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [5743] gdbstub: manage CPUs as threads (Jan Kiszka)
Date: Tue, 18 Nov 2008 21:20:52 +0000
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Jan Kiszka <jan.kiszka@siemens.com>, qemu-devel@nongnu.org

On Tuesday 18 November 2008, Anthony Liguori wrote:
> Paul Brook wrote:
> > On Tuesday 18 November 2008, Anthony Liguori wrote:
> >> Revision: 5743
> >>           http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=5743
> >> Author:   aliguori
> >> Date:     2008-11-18 20:30:24 +0000 (Tue, 18 Nov 2008)
> >>
> >> Log Message:
> >> -----------
> >> gdbstub: manage CPUs as threads (Jan Kiszka)
> >
> > This is wrong. CPUs do not share the same address space, so should be
> > modelled as processes, not threads.
>
> They share the same physical address space.  

GDB works with virtual address spaces. Each CPU has its own MMU, so as soon as 
you load a multitasking OS the chances are that these will look significantly 
different.

> How well does GDB support 
> debugging processes verses threads?  A cursory look seems to suggest the
> thread debugging support is slightly better (thread events) than the
> process debugging support.  They look very similar though.

The thread model can't describe what's actually happening. gdb multiprocess 
support definitely exists (and if it doesn't work right now it's being 
actively worked on), so we should use it.

Paul