linux-kernel - Re: [PATCH v4 4/4] platform/x86: ideapad-laptop: add a mutex to synchronize VPC commands

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Message-ID: <4eab134fc9b9a50c4f870f4d46ddc1415d5df465.camel@irl.hu>
Date: Tue, 30 Jul 2024 18:00:37 +0200
From: Gergo Koteles <soyer@....hu>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: Hans de Goede <hdegoede@...hat.com>,
  Ike Panhc <ike.pan@...onical.com>,
  platform-driver-x86@...r.kernel.org,
  LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 4/4] platform/x86: ideapad-laptop: add a mutex to
 synchronize VPC commands

Hi Ilpo,

On Tue, 2024-07-30 at 16:37 +0300, Ilpo Järvinen wrote:
> On Thu, 25 Jul 2024, Gergo Koteles wrote:
> 
> > Calling VPC commands consists of several VPCW and VPCR ACPI calls.
> > These calls and their results can get mixed up if they are called
> > simultaneously from different threads, like acpi notify handler,
> > sysfs, debugfs, notification chain.
> > 
> > Add a mutex to synchronize VPC commands.
> > 
> > Signed-off-by: Gergo Koteles <soyer@....hu>
> 
> What commit does this fix? I was going to add a Fixes tag myself while 
> applying this but wasn't sure if it should be the ACPI concurrency commit 
> e2ffcda16290 or the change introducing lenovo-ymc driver?
> 

YMC triggering works in 6.7, but not reliably in 6.8. So I assume the
culprit is e2ffcda16290.

But in theory debugfs, sysfs, acpi notify handler can race with each
other in the same way for 10+ years. Technically, probably not.

> Also, I'd prefer to not take the move patch (PATCH 3/4) now so I could 
> take this through fixes branch since it causes a real issue if I remember 
> the earlier discussions right? Do you think there's any issue if I take 
> only patches 1, 2, and 4? They seemed to apply without conflicts when I 
> tried to apply the entire series and then cherrypicked the last patch 
> dropping the third patch.
> 

Yes, this is a real issue.

You can skip the third patch. The series compiles and works fine
without it.

> The code movement patch could go through for-next fixes branch is then 
> merged into it (or after one kernel cycle).
> 
> 

Fine.

Thanks,
Gergo