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Date: Thu, 22 Dec 2005 18:49:17 -0500 (EST)
Subject: Re: [patch 0/9] mutex subsystem, -V4
From: "Sean" <seanlkml@sympatico.ca>
To: "Christoph Hellwig" <hch@infradead.org>
Cc: "Andrew Morton" <akpm@osdl.org>, "Alan Cox" <alan@lxorguk.ukuu.org.uk>,
       arjan@infradead.org, mingo@elte.hu, linux-kernel@vger.kernel.org,
       torvalds@osdl.org, arjanv@infradead.org, nico@cam.org,
       jes@trained-monkey.org, zwane@arm.linux.org.uk, oleg@tv-sign.ru,
       dhowells@redhat.com, bcrl@kvack.org, rostedt@goodmis.org,
       hch@infradead.org, ak@suse.de, rmk+lkml@arm.linux.org.uk
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On Thu, December 22, 2005 6:34 pm, Christoph Hellwig said:
> On Thu, Dec 22, 2005 at 03:30:14PM -0800, Andrew Morton wrote:
>> No it does not.
>>
>> Ingo's work has shown us two things:
>>
>> a) semaphores use more kernel text than they should and
>>
>> b) semaphores are less efficient than they could be.
>>
>> Fine.  Let's update the semaphore implementation to fix those things.
>> Nobody has addressed this code in several years.  If we conclusively
>> cannot
>> fix these things then that's the time to start looking at implementing
>> new
>> locking mechanisms.
>
> c) semaphores are total overkill for 99% percent of the users.  Remember
> this thing about optimizing for the common case?
>
> Pretty much everywhere we do want mutex semantic.  So let's have a proper
> primitive exactly for that, and we can keep the current semaphore
> implementation (with a much simpler implementation) for that handfull of
> users in the kernel that really want a counting semaphore.
>
> I really don't get why you hate mutex primitives so much.
>

Yes it's hard to figure.  It seems to be deeper than just hating mutex
primitives, he hates the timer core updates that come from Ingo too; this
may be a general dislike for all things -rt.

Sean

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