Re: Re: SMP KGDB on ppc64?

On Tuesday 10 Jan 2006 3:13 am, Geoff Levand wrote:
> Tom Rini wrote:
> > On Sat, Jan 07, 2006 at 03:39:23PM -0800, Geoff Levand wrote:
> >>Tom Rini wrote:
> >>>Hey, in your tests were you ever able to get KGDB to reliably always
> >>>sync up all CPUs on an SMP system?  I've found that what we have, at
> >>>least as of kgdb-2-2.6.14 is OK up to the point we come back from a
> >>>stepped into function, and then the 2nd CPU seems to always be lost
> >
> > (gdb
> >
> >>>seems to be switching from the 2nd CPU thread to the actual pid's
> >
> > thread
> >
> >>>and back a bit).  Any ideas if something is missing?  I bumped up
> >>>ROUNDUP_WAIT to 1000000 and that hasn't helped any.  Thanks.
> >>
> >>The last ppc64
> >>patches I sent you were for 2.6.12, and those worked OK (SMP/SMT sync
> >>worked) on PMAC G5 and Cell with both serial and Ether connections.
> >
> > OK.  Can you try the test I've been using of breaking at sys_sync, and
> > then 's 5000' and see if it hangs, or you can continue, or if you get a
> > lot of "Could not sync..." messages?
>
> My implementation uses smp_send_debugger_break, which does not handle
> synchronization objects nor disabled interrupts properly in all cases.
> You'll get 'Not all CPUs have been synced for KGDB'.  I used this
> because it was easy to get something working that could be used for
> simple debugging of device driver code.

This implementation uses smp_call_function, which is a blocking call. You may 
want to implement a send_IPI_allbutself for powerpc64 using smp_cross_call, 
instead. I don't know ppc64 well enough, though I believe this should provide 
a non-blocking way of holding other cpus.

Does powerpc have an NMI like i386, which breaks in regardless of whether 
interrupts are disabled?
-Amit


>
> For more info see 'rounding up CPUs on debug exception':
>
>   http://ozlabs.org/pipermail/linuxppc64-dev/2005-September/005824.html
>
> And the kgdb thread 'problem with kgdb_roundup_cpus() and ppc64':
>
>   http://sourceforge.net/mailarchive/message.php?msg_id=12795853
>
> -Geoff
>
>
>
>
>
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