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

[qiaochong]

sorry. The patch I just sent missing header asm/irqregs.h.
I resent a patch just now.

I use kgdb on loongson 3a platform,  which is 4 core cpu.
Loongson cpu call smp call function by ipi interrupt.

I have tested cpu cmd in kdb and info threads cmd in kgdb with this patch.

Mips save regs and set  pt_regs to  current_thread_info()->regs(TI_REGS($28)) as bellow.

handle_int:
...
SAVE_ALL docfi=1                                                                          CLI                                                                                       TRACE_IRQS_OFF                                                                                                                                                                      LONG_L  s0, TI_REGS($28)
LONG_S  sp, TI_REGS($28)

static inline struct pt_regs *get_irq_regs(void)                                          {
        return current_thread_info()->regs;                                               }

å 2019-03-27 22:37:02ï"Doug Anderson" <dianders@xxxxxxxxxxxx> åéï

>Hi,
>
>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 <https://crbug.com/908723>.
>
>-Doug


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