Re: [newbie] timer in module

[Bart Trojanowski <bart@jukie.net>]

On Fri, 18 May 2001, sebastien person wrote:

> I have a network module that need to regularly get data from network
> adaptater.
> But I don't know if it safe to do a loop with a timer in the module.

First off you have to decide where you want to run your 'get data'.  There
are three context you can pick from: user priority or from the kernel.  If
you run the loop below from a user context then you will have a very
unresponsive system but at least other things will still run.  If you run
that from a kernel context nothing else will run... unless you explicitly
call the scheduler.

> My aim is to do a get data call every x seconds (x is variable).

You mentioned a timer... it runs in kernel context but at least it
will not end up hanging your system up.  This is how you would use one:

struct tq_struct timer;
init_timer(&timer);
timer.routine = func;
timer.data = something;
mod_timer(&timer, 5*HZ); // 5 seconds from now

void func( unsigned long something ) {
	get_data( something );
	mod_timer(&timer, 5*HZ); // again in 5 seconds
}

Make sure you call 'del_timer_sync' once you are done.

> Is it better to let an external program executing timer call and get data
> call via ioctl ?

Since you are getting data every 5 seconds you may as well use a user
space program.  It does not seem like you are looking for phenomenal
responsiveness here.

Bart.

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