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Date: Mon, 25 Feb 2002 09:44:09 -0800 (PST)
From: Linus Torvalds <torvalds@transmeta.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
cc: Rusty Russell <rusty@rustcorp.com.au>, <mingo@elte.hu>,
        Matthew Kirkwood <matthew@hairy.beasts.org>,
        Benjamin LaHaise <bcrl@redhat.com>, David Axmark <david@mysql.com>,
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Subject: Re: [PATCH] Lightweight userspace semaphores...
In-Reply-To: <E16fPGp-0005bj-00@the-village.bc.nu>
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On Mon, 25 Feb 2002, Alan Cox wrote:
> 
> Any kernel special cases it adds will be unswappable because they are in
> kernel space (not the semaphores here - we want them to be swappable and
> they can be)

Alan, wake up!

I'm talking about anonymous semaphores, the kernel implementation can just 
map a normal anonymous page there.

On 99.9% of all machines out there, you can have semaphores in perfectly 
normal memory.

> When you create a shared mapping by passing -1 to mmap we do

Why are you talking about shared mappings?

The most common case for any fast semaphores are for _threaded_
applications. No shared memory, no nothing.

		Linus

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