Message-ID: <439EDC3D.5040808@nortel.com>
Date: Tue, 13 Dec 2005 08:35:41 -0600
From: "Christopher Friesen" <cfriesen@nortel.com>
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To: David Howells <dhowells@redhat.com>
CC: Alan Cox <alan@lxorguk.ukuu.org.uk>, torvalds@osdl.org, akpm@osdl.org,
       hch@infradead.org, arjan@infradead.org, matthew@wil.cx,
       linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: [PATCH 1/19] MUTEX: Introduce simple mutex implementation
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David Howells wrote:
> Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:

>>It seems to me it would be far far saner to define something like
>>
>>	sleep_lock(&foo)
>>	sleep_unlock(&foo)
>>	sleep_trylock(&foo)
> 
> Which would be a _lot_ more work. It would involve about ten times as many
> changes, I think, and thus be more prone to errors.

"lots of work" has never been a valid reason for not doing a kernel 
change...

In this case, introducing a new API means the changes can be made over time.

As time goes on you can convert more and more code to the mutex/sleep 
lock and any tricky code just stays with the older API until someone who 
understands it can vet it.

As Alan mentioned, the standard counting semaphore API is up/down. 
Making those refer to a sleeping mutex violates the principle of least 
surprise.

Chris

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