Re: [PATCH] mips: Fix crash registers on non-crashing CPUs

[Corey Minyard <cminyard@mvista.com>]

Anything on this?

-corey

On 04/11/2016 09:10 AM, minyard@acm.org wrote:
> From: Corey Minyard <cminyard@mvista.com>
>
> As part of handling a crash on an SMP system, an IPI is send to
> all other CPUs to save their current registers and stop.  It was
> using task_pt_regs(current) to get the registers, but that will
> only be accurate if the CPU was interrupted running in userland.
> Instead allow the architecture to pass in the registers (all
> pass NULL now, but allow for the future) and then use get_irq_regs()
> which should be accurate as we are in an interrupt.  Fall back to
> task_pt_regs(current) if nothing else is available.
>
> Signed-off-by: Corey Minyard <cminyard@mvista.com>
> ---
>   arch/mips/kernel/crash.c | 16 +++++++++++++---
>   1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/arch/mips/kernel/crash.c b/arch/mips/kernel/crash.c
> index d434d5d..610f0f3 100644
> --- a/arch/mips/kernel/crash.c
> +++ b/arch/mips/kernel/crash.c
> @@ -14,12 +14,22 @@ static int crashing_cpu = -1;
>   static cpumask_t cpus_in_crash = CPU_MASK_NONE;
>   
>   #ifdef CONFIG_SMP
> -static void crash_shutdown_secondary(void *ignore)
> +static void crash_shutdown_secondary(void *passed_regs)
>   {
> -	struct pt_regs *regs;
> +	struct pt_regs *regs = passed_regs;
>   	int cpu = smp_processor_id();
>   
> -	regs = task_pt_regs(current);
> +	/*
> +	 * If we are passed registers, use those.  Otherwise get the
> +	 * regs from the last interrupt, which should be correct, as
> +	 * we are in an interrupt.  But if the regs are not there,
> +	 * pull them from the top of the stack.  They are probably
> +	 * wrong, but we need something to keep from crashing again.
> +	 */
> +	if (!regs)
> +		regs = get_irq_regs();
> +	if (!regs)
> +		regs = task_pt_regs(current);
>   
>   	if (!cpu_online(cpu))
>   		return;