linux-kernel - Re: "upping" a semaphore from interrupt context?

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Message-ID: <Pine.LNX.4.64.0706231209490.15371@localhost.localdomain>
Date:	Sat, 23 Jun 2007 12:11:57 -0400 (EDT)
From:	"Robert P. J. Day" <rpjday@...dspring.com>
To:	Satyam Sharma <satyam.sharma@...il.com>
cc:	Arnd Bergmann <arnd@...db.de>, Florin Iucha <florin@...ha.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: "upping" a semaphore from interrupt context?

On Sat, 23 Jun 2007, Satyam Sharma wrote:

> Hi Robert, Arnd,
>
> On 6/23/07, Arnd Bergmann <arnd@...db.de> wrote:
> > On Saturday 23 June 2007, Robert P. J. Day wrote:
> > > On Fri, 22 Jun 2007, Arnd Bergmann wrote:
> > > >
> > > > yes, but you should not. The use of semaphores is not recommended
> > > > for new code, it should be replaced with either a mutex or a
> > > > completion.
> > >
> > > can you clarify this? it sounds like you're saying that the current
> > > implementation of semaphores is entirely superfluous. but surely it
> > > isn't possible to replace all semaphores with either mutexes or
> > > completions, is it?
>
> Semaphores being used as completions are superfluous, obsoleted by
> completion handlers. Semaphores that are not counted (hence binary)
> are superfluous, obsoleted by struct mutex.

hang on, how is that true?  as i read it, mutexes are more than just
binary semaphores -- they have additional restrictions that regular
semaphores don't.  so i'm not convinced that binary semaphores can
simply be replaced by mutexes, unless that's not what you meant here.

rday

-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

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