rounding up CPUs on debug exception
Haren Myneni
haren at us.ibm.com
Tue Sep 27 05:18:20 EST 2005
Geoff Levand wrote:
>When kgdb handles a debugging exception (trap or trace for ppc) it
>tries to stop execution on the other CPUs as soon as possible so
>that changes in the system state from the time of the exception
>are minimized. The i386 code (below) uses the inter-processor
>interrupt features of the APIC interrupt controller to send a
>high priority NMI to the other CPUs. An NMI is needed here,
>since another CPU may be waiting with interrupts disabled on a
>spin lock the current cpu holds.
>
>void kgdb_roundup_cpus(unsigned long flags)
>{
> send_IPI_allbutself(APIC_DM_NMI);
>}
>
>I need something similar to support SMP on ppc64. Can anyone
>suggest something?
>
>
Unfortunately, there is no software NMI support on PPC64. It would be
better to have this feature.
However, the user can do soft-reset manually to bring all CPUs into
debugger as xmon does. For this, kgdb has to be modified such it handles
the re-entrant of CPUs which are already responded to an IPI. I
believe, you can re-use some functions (long_jmp and set_jmp) defined
for xmon.
Thanks
Haren
>-Geoff
>
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