linux-kernel - Re: Why there are so many struct rw

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Date:	Wed, 04 Jul 2007 12:34:16 +0200
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Oliver Neukum <oliver@...kum.org>
CC:	jidong xiao <jidong.xiao@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: Why there are so many struct rw_semaphore being
 defined?

Oliver Neukum wrote:
> Am Mittwoch, 4. Juli 2007 schrieb jidong xiao:
>> I see struct rw_semaphore is defined in
>> include/linux/rwsem-spinlock.h,in the meanwhile, I also can find it in
> 
> Quote:
> 
> #ifndef _LINUX_RWSEM_H
> #error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead"
> #endif
> 
>> include/asm-**/rwsem.h,for
>> example,include/asm-i386/rwsem.h,include/asm-x86_64/rwsem.h,why?which
>> one should be used?
> 
> This structure is so important to performance that some architectures
> have version optimized to their features.

...but of course we generally include linux/rwsem.h instead of
architecture-specific header files.  linux/rwsem.h will transparently
pull in the optimized variants for us.  (It's evident from the source.)
-- 
Stefan Richter
-=====-=-=== -=== --=--
http://arcgraph.de/sr/
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