RE: [PATCH] ACPICA: Export mutex functions

[Zheng, Lv]

Hi,

> -----Original Message-----
> From: Moore, Robert
> Sent: Tuesday, April 18, 2017 3:28 AM
> To: 'Guenter Roeck' <linux@xxxxxxxxxxxx>; Zheng, Lv <lv.zheng@xxxxxxxxx>
> Cc: Wysocki, Rafael J <rafael.j.wysocki@xxxxxxxxx>; 'Len Brown' <lenb@xxxxxxxxxx>; 'linux-
> acpi@xxxxxxxxxxxxxxx' <linux-acpi@xxxxxxxxxxxxxxx>; 'devel@xxxxxxxxxx' <devel@xxxxxxxxxx>; 'linux-
> kernel@xxxxxxxxxxxxxxx' <linux-kernel@xxxxxxxxxxxxxxx>; Box, David E <david.e.box@xxxxxxxxx>
> Subject: RE: [PATCH] ACPICA: Export mutex functions
> 
> 
> > -----Original Message-----
> > From: Moore, Robert
> > Sent: Monday, April 17, 2017 10:13 AM
> > To: Guenter Roeck <linux@xxxxxxxxxxxx>; Zheng, Lv <lv.zheng@xxxxxxxxx>
> > Cc: Wysocki, Rafael J <rafael.j.wysocki@xxxxxxxxx>; Len Brown
> > <lenb@xxxxxxxxxx>; linux-acpi@xxxxxxxxxxxxxxx; devel@xxxxxxxxxx; linux-
> > kernel@xxxxxxxxxxxxxxx
> > 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