Re: [PATCH 1/7] platform/x86: fujitsu-laptop: do not use kfifo for storing hotkey scancodes

From: MichaÅ KÄpieÅ
Date: Thu Jun 22 2017 - 16:09:38 EST

> On Fri, Jun 16, 2017 at 06:40:52AM +0200, MichaÅ KÄpieÅ 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,
MichaÅ KÄpieÅ