Re: [PATCH 15/21] mips: octeon: smp: Convert to hotplug state machine

Matt Redfearn
2016-09-07T08:25:14Z

HI Sebastian,

On 06/09/16 18:04, Sebastian Andrzej Siewior wrote:
> Install the callbacks via the state machine.
>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: linux-mips@linux-mips.org
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> arch/mips/cavium-octeon/smp.c | 24 +++---------------------
> include/linux/cpuhotplug.h | 1 +
> 2 files changed, 4 insertions(+), 21 deletions(-)
>
> diff --git a/arch/mips/cavium-octeon/smp.c b/arch/mips/cavium-octeon/smp.c
> index 4d457d602d3b..228c1cab2912 100644
> --- a/arch/mips/cavium-octeon/smp.c
> +++ b/arch/mips/cavium-octeon/smp.c
> @@ -380,29 +380,11 @@ static int octeon_update_boot_vector(unsigned int cpu)
> return 0;
> }
>
> -static int octeon_cpu_callback(struct notifier_block *nfb,
> - unsigned long action, void *hcpu)
> -{
> - unsigned int cpu = (unsigned long)hcpu;
> -
> - switch (action & ~CPU_TASKS_FROZEN) {
> - case CPU_UP_PREPARE:
> - octeon_update_boot_vector(cpu);
> - break;
> - case CPU_ONLINE:
> - pr_info("Cpu %d online\n", cpu);
> - break;
> - case CPU_DEAD:
> - break;
> - }
> -
> - return NOTIFY_OK;
> -}
> -
> static int register_cavium_notifier(void)
> {
> - hotcpu_notifier(octeon_cpu_callback, 0);
> - return 0;
> + return cpuhp_setup_state_nocalls(CPUHP_MIPS_CAVIUM_PREPARE,
> + "mips/cavium:prepare",
> + octeon_update_boot_vector, NULL);

This looks like a nice change which results in much cleaner code

> }
> late_initcall(register_cavium_notifier);
>
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 4cbf88c955d6..058d312fdf6f 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -44,6 +44,7 @@ enum cpuhp_state {
> CPUHP_SH_SH3X_PREPARE,
> CPUHP_X86_MICRCODE_PREPARE,
> CPUHP_NOTF_ERR_INJ_PREPARE,
> + CPUHP_MIPS_CAVIUM_PREPARE,

But I'm curious why we have to create a new state here - this is going
to get very unwieldy if every variant of every architecture has to have
it's own state values in that enumeration. Can this use, what I assume
is (and perhaps could be documented better in
include/linux/cpuhotplug.h), the generic prepare state CPUHP_NOTIFY_PREPARE?

Thanks,
Matt

> CPUHP_TIMERS_DEAD,
> CPUHP_BRINGUP_CPU,
> CPUHP_AP_IDLE_DEAD,