linux-kernel - RE: [PATCH] ACPICA: Export mutex functions

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Date:   Mon, 17 Apr 2017 23:43:12 +0000
From:   "Zheng, Lv" <lv.zheng@...el.com>
To:     "Moore, Robert" <robert.moore@...el.com>,
        'Guenter Roeck' <linux@...ck-us.net>
CC:     "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        'Len Brown' <lenb@...nel.org>,
        "'linux-acpi@...r.kernel.org'" <linux-acpi@...r.kernel.org>,
        "'devel@...ica.org'" <devel@...ica.org>,
        "'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
        "Box, David E" <david.e.box@...el.com>
Subject: RE: [PATCH] ACPICA: Export mutex functions

Hi,

> -----Original Message-----
> From: Moore, Robert
> Sent: Tuesday, April 18, 2017 3:28 AM
> To: 'Guenter Roeck' <linux@...ck-us.net>; Zheng, Lv <lv.zheng@...el.com>
> Cc: Wysocki, Rafael J <rafael.j.wysocki@...el.com>; 'Len Brown' <lenb@...nel.org>; 'linux-
> acpi@...r.kernel.org' <linux-acpi@...r.kernel.org>; 'devel@...ica.org' <devel@...ica.org>; 'linux-
> kernel@...r.kernel.org' <linux-kernel@...r.kernel.org>; Box, David E <david.e.box@...el.com>
> Subject: RE: [PATCH] ACPICA: Export mutex functions
> 
> 
> > -----Original Message-----
> > From: Moore, Robert
> > Sent: Monday, April 17, 2017 10:13 AM
> > To: Guenter Roeck <linux@...ck-us.net>; Zheng, Lv <lv.zheng@...el.com>
> > Cc: Wysocki, Rafael J <rafael.j.wysocki@...el.com>; Len Brown
> > <lenb@...nel.org>; linux-acpi@...r.kernel.org; devel@...ica.org; linux-
> > kernel@...r.kernel.org
> > Subject: RE: [PATCH] ACPICA: Export mutex functions
> >
> > There is a model for the drivers to directly acquire an AML mutex
> > object. That is why the acquire/release public interfaces were added to
> > ACPICA.
> >
> > I forget all of the details, but the model was developed with MS and
> > others during the ACPI 6.0 timeframe.
> >
> >
> [Moore, Robert]
> 
> 
> Here is the case where the OS may need to directly acquire an AML mutex:
> 
> From the ACPI spec:
> 
> 19.6.2 Acquire (Acquire a Mutex)
> 
> Note: For Mutex objects referenced by a _DLM object, the host OS may also contend for ownership.
> 
> 
> 
> 
> Other than this case, the OS/drivers should never need to directly acquire an AML mutex.

That sounds reasonable but the driver might invoke an ACPICA API accessing the _DLM returned mutexes.

Thanks and best regards
Lv