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SubjectRe: [newbie] timer in module
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;
timer.routine = func; = 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.



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