Date: Thu, 22 Jun 2017 22:08:56 +0200
From: =?utf-8?B?TWljaGHFgiBLxJlwaWXFhA==?= <kernel@kempniu.pl>
To: Darren Hart <dvhart@infradead.org>
Cc: Rafael Wysocki <rjw@rjwysocki.net>,
        Jonathan Woithe <jwoithe@just42.net>,
        Andy Shevchenko <andy@infradead.org>,
        platform-driver-x86@vger.kernel.org, linux-acpi@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/7] platform/x86: fujitsu-laptop: do not use kfifo for
 storing hotkey scancodes
Message-ID: <20170622200856.GA4194@kmp-mobile.hq.kempniu.pl>
References: <20170616044058.30443-1-kernel@kempniu.pl>
 <20170616044058.30443-2-kernel@kempniu.pl>
 <20170621181543.GB25900@fury>
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> On Fri, Jun 16, 2017 at 06:40:52AM +0200, Michał Kępień wrote:
> > All ACPI device notify callbacks are invoked using acpi_os_execute(),
> > which causes the supplied callback to be queued to a static workqueue
> > which always executes on CPU 0.  This means that there is no possibility
> > for any ACPI device notify callback to be concurrently executed on
> > multiple CPUs, which in the case of fujitsu-laptop means that using a
> > locked kfifo for handling hotkeys is redundant: as hotkey scancodes are
> > only pushed and popped from within acpi_fujitsu_laptop_notify(), no risk
> > of concurrent pushing and popping exists.
> 
> Was the kfifo causing a problem currently or for the migration to separate
> modules? Is this purely a simplification?

It is just another step in stripping fujitsu-laptop down to its bare
essentials.  If my reasoning quoted above is correct, using a locked
kfifo needlessly suggests potential concurrency issues, but it is
definitely not an error.

-- 
Best regards,
Michał Kępień