netdev - Re: Kernel rwlock design, Multicore and IGMP

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Date:	Sat, 13 Nov 2010 14:35:51 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Cypher Wu <cypher.w@...il.com>
Cc:	Américo Wang <xiyou.wangcong@...il.com>,
	Yong Zhang <yong.zhang0@...il.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	linux-kernel@...r.kernel.org, netdev <netdev@...r.kernel.org>
Subject: Re: Kernel rwlock design, Multicore and IGMP

On Fri, Nov 12, 2010 at 07:06:47PM +0800, Cypher Wu wrote:
>>
>> Note, on Tile, it uses a little different algorithm.
>>
>
>It seems that rwlock on x86 and tile have different behavior, x86 use
>RW_LOCK_BIAS, when read_lock() it will test if the lock is 0, and if
>so then the read_lock() have to 'spinning', otherwise it dec the lock;
>when write_lock() tried it first check if lock is It seems that rwlock
>on x86 and tile have different behavior, x86 use RW_LOCK_BIAS and if
>so, set lock to 0 and continue, otherwise it will 'spinning'.
>I'm not very familiar with x86 architecture, but the code seems like
>working that way.

No, they should be the same, sorry I made a mistake in the above reply.

Although Tile uses shifts in implementation while x86 uses inc/dec,
the idea is same, either writers use higher bits and readers use
lower bits or vice-versa.

-- 
Live like a child, think like the god.
 
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