Subj : Re: Help with timers/signals
To   : comp.programming.threads
From : Sean Burke
Date : Fri Mar 11 2005 01:49 am


"vinay" <vinaymathew80@yahoo.com> writes:

> Hi guys,
> Im new to programming with linux and its timers and signal handlers.Can
> any one suggest a possible solution to the problem im having.The
> problem is described as follows
> I have an array of queues.Say 10.Now i go thro this array 1 by 1 and
> dequeue elements from each queue.This is simple.My problem now is this
> dequeuing.Every element needs to be dequeued at a particular point in
> time.Hence i need to set different timers/signals for the different
> times that each element will be dequeued.Is there any way of specifying
> this functionality using signals/timers.Example:i need to specify an
> alarm that goes off at 20ms for the 1 element then at 50ms(after 30ms)
> for the 2nd element then at 10ms(this timer will go off first actually)
> for the 3 element.And the action for the alarm is the dequeue function
> that will dequeue the element whose timer expired from the particular
> queue. Also Can this queue parameter also be passed to the handler
> function?? cos as per the documentation for the signal handler it takes
> only 1 argument signum. Is it possible to send more arguments to the
> handler from the signal call??
> I dont know if its possible but is there a way of specifying user
> defined signals in linux.I was thinking of having 10 user defined
> signals for the 10 queues that i have.And every time a timer expires in
> a particular queue i need to send the signal associated with that
> queue.Is this possible in linux.I have just come across the alarm and
> some other standard signals which are generated and hence this does not
> suit my need.
> Thanx in advance for ur suggestions ...... ive been racking my brains
> for this one...would indeed be a great help to get some pointers on
> this. 
> thanx and kind regards
> vinay

While timers may look like they should be a good solution to this
problem, I have also found that in practice they aren't very easy
to use, particularly in view of the issues that attend the use of
signals in threaded code.

The Nifty library contains thread-based timer package that should 
be a good match to your requirement. The code is free to use, and
you can download it from

  ftp://ftp.xenadyne.com/pub/Nifty.tgz

-SEan

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