[oggonachip] Re: pthread_cancel()

[Pattara Kiatisevi]

On Thu, 14 Mar 2002, Aaron J. Grier wrote:

> On Thu, Mar 14, 2002 at 11:14:05AM +0100, Pattara Kiatisevi wrote:
>
> > Is there concept of rendezvous in classsic API? E.g. how would you
> > implement this scenario? (It is not certain that task1 will connect to
> > task2.meet() before or after task2 is waiting at task2.meet())
> >
> > Task 1:				Task2:
> >
> > <run whatever>			<run whatever>
> >
> > Connect task2.meet() ----------> Wait task2.meet()
> > 				 <meeting point code, run while task1
> > 				  blocks>
> >
> > <run whatever>			<run whatever>
>
> use a simple binary semaphore.

Hmm, but in case that task2 is faster than task1, then it released while
noone was waiting (for obtaining). And then task1 blocks later, waiting
for task2 to release whenever later. So it does not really correspond to
the above rendezvous scheme? (whoever who is faster will wait for another
one and go together). Do I miss sth?

Thanks,
Pattara

>
> rtems_id	semaphore;
> rtems_name	semaphore_name;
>
> status = rtems_semaphore_create(
>     semaphore_name,
>     0,
>     RTEMS_SIMPLE_BINARY_SEMAPHORE,
>     RTEMS_NO_PRIORITY,
>     &semaphore
> );
>
> task 1:					task 2:
>
> <run whatever>				<run whatever>
>
> rtems_semaphore_obtain(			<still running>
>     semaphore,
>     RTEMS_WAIT,
>     RTEMS_NO_TIMEOUT
> );
>
> <blocked>				<still running>
>
> 					rtems_semaphore_release(
> 					    semaphore
> 					);
>
> <starts running>			<continues on>
>
> in this case task2 continues to run regardless of whether or not task1
> is blocked.  it is completely up to task1 to complete its work before
> task2 performs another release().  (task2 could tell whether or not
> task1 was blocking by checking the return status of the release() call.)
>
> I use this system in my audio device driver.  :)  "task 2" in my case is
> an ISR which moves buffer data to and from the sound card, and "task 1"
> is the read() and write() calls of the device driver.
>
> --
>   Aaron J. Grier  |   Frye Electronics, Tigard, OR   |  aaron at frye.com
>      "In a few thousand years people will be scratching their heads
>        wondering how on earth the first computer was invented and
>           bootstrapped without a prior computer to do it with."
>                     --  Chris Malcolm, on comp.arch
>
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