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

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Date:   Mon, 17 Apr 2017 19:27:37 +0000
From:   "Moore, Robert" <robert.moore@...el.com>
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.
Bob