[SRU][Bionic][PATCH 1/2] powerpc: use NMI IPI for smp_send_stop

[Joseph Salisbury]

On 06/22/2018 12:08 PM, Joseph Salisbury wrote:
> From: Nicholas Piggin <npiggin at gmail.com>
>
> BugLink: http://bugs.launchpad.net/bugs/1777194
>
> Use the NMI IPI rather than smp_call_function for smp_send_stop.
> Have stopped CPUs hard disable interrupts rather than just soft
> disable.
>
> This function is used in crash/panic/shutdown paths to bring other
> CPUs down as quickly and reliably as possible, and minimizing their
> potential to cause trouble.
>
> Avoiding the Linux smp_call_function infrastructure and (if supported)
> using true NMI IPIs makes this more robust.
>
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
> (cherry picked from commit 6bed3237624e3faad1592543952907cd01a42c83)
> Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
> ---
>  arch/powerpc/kernel/smp.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index bbe7634..378112c 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -565,7 +565,11 @@ void crash_send_ipi(void (*crash_ipi_callback)(struct pt_regs *))
>  }
>  #endif
>  
> +#ifdef CONFIG_NMI_IPI
> +static void stop_this_cpu(struct pt_regs *regs)
> +#else
>  static void stop_this_cpu(void *dummy)
> +#endif
>  {
>  	/* Remove this CPU */
>  	set_cpu_online(smp_processor_id(), false);
> @@ -577,7 +581,11 @@ static void stop_this_cpu(void *dummy)
>  
>  void smp_send_stop(void)
>  {
> +#ifdef CONFIG_NMI_IPI
> +	smp_send_nmi_ipi(NMI_IPI_ALL_OTHERS, stop_this_cpu, 1000000);
> +#else
>  	smp_call_function(stop_this_cpu, NULL, 0);
> +#endif
>  }
>  
>  struct thread_info *current_set[NR_CPUS];

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