linux-kernel - Re: [PATCH v0] add nano semaphore in kernel

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Message-ID: <20110104140355.GA1707@ucw.cz>
Date:	Tue, 4 Jan 2011 15:03:55 +0100
From:	Pavel Machek <pavel@....cz>
To:	Hillf Danton <dhillf@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v0] add nano semaphore in kernel

Hi!

> +/*
> + * nano_semaphore_down - acquire the nano semaphore
> + * @s: the nano semaphore to be acquired
> + * @nano_secs: the nano seconds to wait if necessary,
> + *		could be zero if want to wait as long as possible.
> + *
> + * Returns >0 if acquired successfully, <=0 otherwise.
> + *
> + * Note unlike down() in semaphore, nano_semaphore_down is not looping until
> + * the nano semaphore is hold, but simply reports the result. And the callers
> + * could, if they like, loop in simple manner, for instance,
> + *	while (1 != nano_semaphore_down(s, 800));
> + *	do_home_work();
> + *	nano_semaphore_up(s);

But thats spinlock, not semaphore, right?

Also, your example does not use the API right -- according to
description, 42 is correct 'semaphore acquired' reply...

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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