linux-kernel - Re: [PATCH V3] firmware: google: Test spinlock on panic path to avoid lockups

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Date:   Thu, 1 Sep 2022 15:13:20 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Petr Mladek <pmladek@...e.com>, evgreen@...omium.org,
        arnd@...db.de, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel@...ccoli.net, ardb@...nel.org,
        davidgow@...gle.com, jwerner@...omium.org
Subject: Re: [PATCH V3] firmware: google: Test spinlock on panic path to
 avoid lockups

On Thu, 1 Sep 2022 16:02:08 -0300 "Guilherme G. Piccoli" <gpiccoli@...lia.com> wrote:

> On 01/09/2022 15:59, Greg KH wrote:
> > [...]
> > Ick, I don't know, this all feels odd.  I want someone else to review
> > this and give their ack on the patch before I'll take it so someone else
> > can share in the blame :)
> > 
> > thanks,
> > 
> > greg k-h
> 
> LOL, that's OK for me! Evan seems to be fine with it BTW.
> 
> Let's see if Petr can jump in, also adding Andrew here since he's
> usually merging stuff for panic.

Are the usual gsmi developers not operational?

Patch seems sensible to me, although the deadlock sounds pretty
theoretical.  A better code comment might be simply

	/*
	 * Panic callbacks are executed with all other CPUs stopped, so we must
	 * not attempt to spin waiting for gsmi_dev.lock to be released.
	 */

?