linux-kernel - Re: x86: clean up rwsem type system

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Message-ID: <4B4EC1A5.4010701@zytor.com>
Date:	Wed, 13 Jan 2010 23:03:01 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: x86: clean up rwsem type system

On 01/12/2010 06:16 PM, Linus Torvalds wrote:
> 
> In case anybody wants to test, the final piece is appended.
> 
> Again, note the 32767-thread limit here. So this really does need that 
> whole "make rwsem_count_t be 64-bit and fix the BIAS values to match" 
> extension on top of it, but that is conceptually a totally independent 
> issue.
> 
> NOT TESTED! The original patch that this all was based on were tested by 
> KAMEZAWA Hiroyuki, but maybe I screwed up something when I created the 
> cleaned-up series, so caveat emptor..
> 
> Also note that it _may_ be a good idea to mark some more registers 
> clobbered on x86-64 in the inline asms instead of saving/restoring them. 
> They are inline functions, but they are only used in places where there 
> are not a lot of live registers _anyway_, so doing for example the 
> clobbers of %r8-%r11 in the asm wouldn't make the fast-path code any 
> worse, and would make the slow-path code smaller. 
> 

Hi Linus,

I have put these into a separate topic branch in the tip tree, which
should get them some test coverage.  I will look at 64-bit counters to
support 2^31 threads hopefully later this week, unless you prefer to do
it yourself.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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