linux-kernel - Re: [PATCH] RFC: console: hack up console

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Message-ID: <20190510095141.GA32171@jagdpanzerIV>
Date:   Fri, 10 May 2019 18:51:41 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        John Ogness <john.ogness@...utronix.de>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] RFC: console: hack up console_lock more v3

On (05/10/19 11:15), Petr Mladek wrote:
[..]
>  arch/x86/kernel/smp.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> --- a/arch/x86/kernel/smp.c
> +++ b/arch/x86/kernel/smp.c
> @@ -124,7 +124,8 @@ static bool smp_no_nmi_ipi = false;
>   */
>  static void native_smp_send_reschedule(int cpu)
>  {
> -	if (unlikely(cpu_is_offline(cpu))) {
> +	if (unlikely(cpu_is_offline(cpu) &&
> +		     atomic_read(&stopping_cpu) < 0)) {
>  		WARN(1, "sched: Unexpected reschedule of offline CPU#%d!\n", cpu);
>  		return;
>  	}

I think we need to remove CPU which we IPI_STOP from
idle_cpus_mask. So then scheduler won't pick up stopped
CPUs (cpumask_first(nohz.idle_cpus_mask)) and attempt
rescheduling to them. It seems that currently
native_stop_other_cpus() doesn't do that.

	-ss