linux-kernel - Re: Semaphores with timeouts

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Message-ID: <20080214001454.4e8cb0eb@core>
Date:	Thu, 14 Feb 2008 00:14:54 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"Ricardo J. Rodríguez" <ricardo.rdez@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Semaphores with timeouts

On Thu, 14 Feb 2008 01:08:28 +0100
"Ricardo J. Rodríguez" <ricardo.rdez@...il.com> wrote:

> Hi everybody,
> I'm developing a driver to support a new protocol on the kernel 2.6.x,
> a real time communication protocol used in robotic fields. Skipping
> the intro: I need to know if there is any function in the kernel to
> get the process sleeping, as down_interruptible(...), but with
> timeouts, I mean, I want the process to wake up if no signal is
> detected in a while...

The Unix world normally expects rather different behaviour

With O_NDELAY set -> no delay but -EAGAIN
Normal -> delay until error or completes or EOF

and the use of poll/select to wait until the event can be issued and is
going to complete. Hence the lack of a mutex_lock_interruptible_timeout()


It's certainly possible to add one but the first question would be "why
do you need it - what sort of API are you trying to build"

Alan
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