linux-kernel - Re: [PATCH] arm: Preserve TPIDRURW on context switch

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Message-ID: <51167CE5.6060303@dawncrow.de>
Date:	Sat, 09 Feb 2013 17:44:21 +0100
From:	André Hentschel <nerv@...ncrow.de>
To:	Will Deacon <will.deacon@....com>
CC:	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] arm: Preserve TPIDRURW on context switch

Am 08.02.2013 16:48, schrieb Will Deacon:
> On Wed, Feb 06, 2013 at 11:01:23PM +0000, André Hentschel wrote:
>> Am 06.02.2013 23:51, schrieb Russell King - ARM Linux:
>>> On Wed, Feb 06, 2013 at 11:43:10PM +0100, André Hentschel wrote:
>>>> There are more and more applications coming to WinRT, Wine could support them,
>>>> but mostly they expect to have the thread environment block (TEB) in TPIDRURW.
>>>> This register must be preserved per thread instead of being cleared.
>>>
>>> I'd prefer this was done a little more sensitively to those CPUs where
>>> loads/stores are expensive, namely:
>>>
>>>> +
>>>> +	@ preserve TPIDRURW register state
>>>> +	get_tls2	r3, r4, r5
>>>> +	str	r3, [r1, #TI_TP2_VALUE]
>>>> +	ldr	r3, [r2, #TI_TP2_VALUE]
>>>> +	set_tls2	r3, r4, r5
>>>
>>> those two loads/stores get omitted from the thread switching if the CPU
>>> doesn't support it.  Do you think that's something you could do?
>>
>> No, i'm not sure how to improve this. How does the process can continue, can you or someone else fix that and add his Signed-off-by?
> 
> How about something like the (completely untested) diff below?
> 
> Andre: if this works for you, I'm happy to write a commit message etc.
> 
> Cheers,
> 
> Will
> 
> --->8

I'll try the next days and report back, thx.
-- 

Best Regards, André Hentschel
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