Semaphores with timeouts

Semaphores with timeouts

[Ricardo J. Rodríguez]

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...

Thanks anyway,
-- 
Ricardo J. Rodríguez
www.deathhc.tk

#329385 | [Registered Linux User]

Re: Semaphores with timeouts

[Alan Cox]

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

Re: Semaphores with timeouts

[Ricardo J. Rodríguez]

Hi Alan,

> 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"
>

The protocol works in adhoc wireless mode, so when I send a packet,
I've to wait a  while before I send it again, like TCP timeout
retransmistions work.

Anyway, I've though maybe I can use SIGALRM to know when it expired
and do whatever...

-- 
Ricardo J. Rodríguez
www.deathhc.tk

#329385 | [Registered Linux User]