linux-kernel - Re: [patch 18/18] sched: Enable smp_processor

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Date:   Mon, 15 May 2017 11:12:57 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [patch 18/18] sched: Enable smp_processor_id() checks early

On Sun, 14 May 2017 20:27:34 +0200
Thomas Gleixner <tglx@...utronix.de> wrote:

> smp_processor_id() checks are enabled after the boot process is done. That
> hides bugs in the smp bringup and driver initialization code.
> 
> Enable it right before the first non-boot CPU is brought up.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  init/main.c            |    3 +++
>  lib/smp_processor_id.c |    2 +-
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  init/main.c            |    3 +++
>  lib/smp_processor_id.c |    2 +-
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1025,6 +1025,9 @@ static noinline void __init kernel_init_
>  	 */
>  	set_cpus_allowed_ptr(current, cpumask_of(raw_smp_processor_id()));
>  
> +	/* Enable smp_processor_id() checks */
> +	system_state = SYSTEM_BOOTING_SMP;
> +

Just a nit, but why set this here and not just before
smp_prepare_cpus()? Anyway...


Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve


>  	cad_pid = task_pid(current);
>  
>  	smp_prepare_cpus(setup_max_cpus);
> --- a/lib/smp_processor_id.c
> +++ b/lib/smp_processor_id.c
> @@ -28,7 +28,7 @@ notrace static unsigned int check_preemp
>  	/*
>  	 * It is valid to assume CPU-locality during early bootup:
>  	 */
> -	if (system_state != SYSTEM_RUNNING)
> +	if (system_state < SYSTEM_BOOTING_SMP)
>  		goto out;
>  
>  	/*
>