Re: [rtl] RTLinux concepts....

[Michael Barabanov <baraban@zappa.spb.su>]

Hello, James,

James Cassidy (jcassidy@nova.genesoft.com) wrote:
> If I want to have a rt fuction called *once* but at a specific
> delay later, I do a:
> 
>       rt_task_init( &doOnceTask, doOnce, 1, 3000, 4 );
>       rt_task_make_periodic( &doOnceTask, rt_get_time() + delay, somePeriod );
> 
> 
> Then in the function to be called only once, at time now+delay:
> 
>       void once( int t ) { 
>            // do something interesting....
> 
>            // stop and further invocations
>            rt_task_suspend( &doOnceTask );
> 
>            rt_task_wait();
>       }
> 
> 
> Some questions...
> 
> Is this the best way to use the rt functions to have a function called
> once, but at a precise time from now?

Seems like there's no a simpler way to do it with the standard scheduler.
There's the rt_task_delay function in the RT-IPC module (see below).

> Is it ok to call rt_task_suspend from within the task that's being suspended?
Yes.

> Is the call to rt_task_wait not required?  If I've already suspended the
> task, should I just return?	  

The call to rt_task_wait is not required. The rt_task_suspend function will not
return (unless you call the rt_wakeup_task function from another task).

> Does returning from a task implicitly do a suspend on that task?
When the task function returns, the task is deleted.

> If I have one task that's updating a variable for other tasks to use, what
> functions are available for mutual exclusion?  	

Check out Jerry Epplin's RT-IPC module at http://stereotaxis.wustl.edu/~jerry/

Michael.

--- [rtl] ---
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http://www.rtlinux.org/