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Date: Tue, 03 Feb 2009 22:55:26 +0100
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To: Andrew Morton <akpm@linux-foundation.org>
CC: Jonathan Corbet <corbet@lwn.net>, linux-kernel@vger.kernel.org,
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Subject: Re: [PATCH 2/4] Convert epoll to a bitlock
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Andrew Morton a écrit :
> On Mon,  2 Feb 2009 11:20:09 -0700
> Jonathan Corbet <corbet@lwn.net> wrote:
> 
>> Matt Mackall suggested converting epoll's ep_lock to a bitlock as a way of
>> saving space in struct file.  This patch makes that change.
> 
> hrm.  bit_spin_lock() makes people upset (large penguiny people).  iirc
> it doesn't have all the correct/well-understood memory/compiler
> ordering semantics which spinlocks have.  And lockdep doesn't know about
> it.
> 

In a previous attempt (2005), I suggested using a single global lock.

http://search.luky.org/linux-kernel.2005/msg50862.html

Probably an array of hashed spinlocks would be more than enough.