linux-kernel - Re: [PATCH] host1x: cdma: use completion instead of semaphore

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Date:   Tue, 11 Dec 2018 11:27:10 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Mikko Perttunen <cyndis@...si.fi>,
        Dmitry Osipenko <digetx@...il.com>, emil.fsw@...de.io,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "open list:TEGRA ARCHITECTURE SUPPORT" <linux-tegra@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] host1x: cdma: use completion instead of semaphore

On Tue, Dec 11, 2018 at 11:11:38AM +0100, Arnd Bergmann wrote:
> On Tue, Dec 11, 2018 at 11:08 AM Thierry Reding
> <thierry.reding@...il.com> wrote:
> >
> > On Mon, Dec 10, 2018 at 10:51:04PM +0100, Arnd Bergmann wrote:
> > > In this usage, the two are completely equivalent, but the
> > > completion documents better what is going on, and we generally
> > > try to avoid semaphores these days.
> > >
> > > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > > ---
> > >  drivers/gpu/host1x/cdma.c | 6 +++---
> > >  drivers/gpu/host1x/cdma.h | 4 ++--
> > >  2 files changed, 5 insertions(+), 5 deletions(-)
> >
> > My understanding is that potentially many userspace processes could be
> > blocking on this, which I think is the reason for it being a semaphore.
> > Is the completion going to work for those cases as well?
> 
> Yes, it behaves the exact same way here.

Great, I'll queue this for v4.22.

Thanks,
Thierry

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