From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=Iwpa=OO=gmail.com=sergey.senozhatsky.work@kernel.org>
Date: Wed, 5 Dec 2018 17:00:44 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Feng Tang <feng.tang@intel.com>, Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>, akpm@linux-foundation.org, bp@suse.de,
	keescook@chromium.org, mm-commits@vger.kernel.org,
	sergey.senozhatsky@gmail.com, stable@vger.kernel.org,
	tglx@linutronix.de, Steven Rostedt <rostedt@goodmis.org>,
	Sasha Levin <sashal@kernel.org>, Andi Kleen <ak@linux.intel.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: + panic-avoid-the-extra-noise-dmesg.patch added to -mm tree
Message-ID: <20181205080044.GA11190@jagdpanzerIV>
References: <20181204071531.z62N9NwXC%akpm@linux-foundation.org>
 <20181204102033.ltdvc7gmev2gvlkq@pathway.suse.cz>
 <20181204154936.wbgcovzpc54n6dvs@shbuild888>
 <20181205022654.GA503@jagdpanzerIV>
 <20181205024713.nqyt6qiamokq7qtl@shbuild888>
 <20181205025728.GC503@jagdpanzerIV>
 <20181205052912.GA423@jagdpanzerIV>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20181205052912.GA423@jagdpanzerIV>
List-ID: <stable.vger.kernel.org>

On (12/05/18 14:29), Sergey Senozhatsky wrote:
> On (12/05/18 11:57), Sergey Senozhatsky wrote:
> > On (12/05/18 10:47), Feng Tang wrote:
>
> OK... So, apparently, what's happening is panic() calls smp_send_stop().
> And smp_send_stop()->native_stop_other_cpus() on x86 disables local APIC.
> So no fun anymore.
>
> If I keep APIC enabled on panic CPU, then I have my keyboard working,
> including PageUp-PageDown scrolling, sysrq handling, and so on.

Meeh, it's much harder than this. Worked on one machine only.

> PeterZ,
>   for those folks who sometimes have to use framebuffer for debugging
>   (just a trivial "let me scrollback and see the panic backtrace") and
>   not always have access to serial console, can we have local APIC
>   enabled on the panic_cpu? Or is it a terrible thing to ask for?

The question remains: can we have input irqs on panic_cpu after panic?

	-ss