Re: [PATCH] MIPS: KGDB: fix kgdb support for SMP platforms.

From: Doug Anderson
Date: Wed Mar 27 2019 - 10:37:19 EST


On Wed, Mar 27, 2019 at 6:17 AM qiaochong <qiaochong@xxxxxxxxxxx> wrote:
> KGDB_call_nmi_hook is called by other cpu through smp call.
> MIPS smp call is processed in ipi irq handler and regs is saved in
> handle_int.
> So kgdb_call_nmi_hook get regs by get_irq_regs and regs will be passed
> to kgdb_cpu_enter.
> Signed-off-by: qiaochong <qiaochong@xxxxxxxxxxx>
> ---
> arch/mips/kernel/kgdb.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> diff --git a/arch/mips/kernel/kgdb.c b/arch/mips/kernel/kgdb.c
> index 6e574c02e4c3b..6c438a0fd2075 100644
> --- a/arch/mips/kernel/kgdb.c
> +++ b/arch/mips/kernel/kgdb.c
> @@ -214,7 +214,7 @@ void kgdb_call_nmi_hook(void *ignored)
> old_fs = get_fs();
> set_fs(KERNEL_DS);
> - kgdb_nmicallback(raw_smp_processor_id(), NULL);
> + kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
> set_fs(old_fs);
> }

I'm excited to see others using kgdb! :-)

As far as I can tell your patch is good, or at least as seems like it
will make MIPS on par with other platforms. I always wondered why
MIPS (and ARC) didn't have the get_irq_regs() call but when I last
touched this code I left it alone since I didn't have the history for
it and had no way to test. Since it seems like you have a way to test
this then we should do it. Now to find someone who would do the same
for ARC. :-P Thus:

Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>

NOTE as pointed out in code reviews when I last touched this code,
using get_irq_regs() isn't perfect since it could plausibly return
NULL. I created a bug in the Chromium tracker with all the details
for this at <>.