On Fri, May 09, 2014 at 01:48:17AM +0100, Geoff Levand wrote:
> Add two new minimal routines smp_spin_table_cpu_disable() and
> smp_spin_table_cpu_die() and hook them up to the smp_spin_table_ops instance.
>
> Kexec support will use smp_spin_table_cpu_die() for re-boot of spin table CPUs,
> but also needs a compatible smp_spin_table_cpu_disable() to allow
> execution to reach smp_spin_table_cpu_die().
>
> Signed-off-by: Geoff Levand <geoff at infradead.org>
> ---
> arch/arm64/kernel/smp_spin_table.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/arch/arm64/kernel/smp_spin_table.c b/arch/arm64/kernel/smp_spin_table.c
> index 7a530d2..26c780b 100644
> --- a/arch/arm64/kernel/smp_spin_table.c
> +++ b/arch/arm64/kernel/smp_spin_table.c
> @@ -142,10 +142,23 @@ static void smp_spin_table_cpu_postboot(void)
> raw_spin_unlock(&boot_lock);
> }
>
> +static int smp_spin_table_cpu_disable(unsigned int cpu)
> +{
> + return 0;
If we cannot kill the CPU then we need to fail here. cpu_disable is
called early enough that the cpu hotplug infrastructure can recover if
we cannot disable the CPU.
> +}
> +
> +static void smp_spin_table_cpu_die(unsigned int cpu)
> +{
> + while (1)
> + cpu_relax();
This does not kill the CPU -- it's stuck spinning on some instructions
that might get clobbered upon a kexec. So this is insufficient for
kexec.
This also doesn't allow the CPU to be brought back, so it's completely
useless as-is.
NAK for pseudo-hotplug. If we cannot place the CPU somewhere out of the
way of the kernel then we _must_ fail.
Thanks,
Mark.
> +}
> +
> const struct cpu_operations smp_spin_table_ops = {
> .name = "spin-table",
> .cpu_init = smp_spin_table_cpu_init,
> .cpu_prepare = smp_spin_table_cpu_prepare,
> .cpu_boot = smp_spin_table_cpu_boot,
> .cpu_postboot = smp_spin_table_cpu_postboot,
> + .cpu_disable = smp_spin_table_cpu_disable,
> + .cpu_die = smp_spin_table_cpu_die,
> };
> --
> 1.9.1
>
>
>
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