Re: gdbstub.c CPU clusters not handled for ThreadInfo packets

[Alistair Francis]

On Tue, Jun 2, 2020 at 10:27 AM Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Tue, 2 Jun 2020 at 18:19, Fabien Chouteau <chouteau@adacore.com> wrote:
> > Le mar. 2 juin 2020 à 18:44, Peter Maydell <peter.maydell@linaro.org> a 
> > écrit :
> > >
> > > By default gdb does not attach to all clusters (this is IIRC something
> > > that can't
> > > be influenced on the QEMU end);
> >
> > You mean I cannot have QEMU attach all clusters by default?
>
> I mean that the end of the gdb remote protocol connection that
> decides what to attach to is gdb, not QEMU. In theory gdb could
> be improved to automatically attach to all available inferiors,
> or the remote protocol could be improved to allow the QEMU end
> to say "I recommend you attach to inferiors X, Y and Z". But
> at the moment that doesn't exist so the best you can do I suspect
> is going to be to script gdb to do the attaching without you
> having to type the commands yourself.
>
> > > are you explicitly asking it to attach to the second cluster?
> >
> > So far the behavior that we had was to see all the CPUs without asking
> > explicitly.
> > I want to go back to that behavior because the current situation is a
> > huge drawback for our users.
>
> That works when there's only one cluster. When there's multiple
> clusters, by default gdb will show you all the CPUs in the first
> cluster. Would the behaviour be better if the other cluster in
> this machine was the first (default) one?
>
> > > https://lists.nongnu.org/archive/html/qemu-devel/2020-01/msg07035.html
> > > is a mailing list post from January which gives the gdb commands which
> > > ought to cause it to attach to the second cluster on this machine.
> >
> > The commands:
> >         target extended-remote :1234
> >         add-inferior
> >         inferior 2
> >         attach 2
> >         set schedule-multiple
> >         info threads

I just updated the QEMU RISC-V wiki to include these steps:

https://wiki.qemu.org/Documentation/Platforms/RISCV#Attaching_GDB

Alistair

> >
> > Do not work for me, "attach 2" in GDB asks me to kill the debugged program.
>
> Hmm. That's the behavior for 'target remote' but 'target extended-remote'
> ought to support multiple inferiors. What gdb version is this?
>
> thanks
> -- PMM
>