[ECOS] How to reset the timeout on a thread waiting for a fla g

Fabrice Gautier Fabrice_Gautier@sdesigns.com
Fri Jan 31 17:32:00 GMT 2003


> -----Original Message-----
> From: Jonathan Larmour [mailto:jifl@eCosCentric.com]
> Sent: Monday, January 27, 2003 8:33 PM
> To: Fabrice Gautier
> Cc: Ecos-List (E-mail)
> Subject: Re: [ECOS] How to reset the timeout on a thread waiting for a
> flag
> 
> 
> Fabrice Gautier wrote:
> > Hi,
> > 
> > Here is what i want to do:
> > 
> > I have a thread starting an operation and waiting for it to 
> > finish. The operation result in a series of interrupts.
> > The thread waits on a flag, and the ISR will eventually set
> > the flag when the operation is done, to wake up the thread. 
> 
> DSR I hope :-).

Well... actually no... Is it safe do that in the ISR? I guess not... but i'm
not sure why. How does the cyg_flag_set function blocks? 

Anyway I''m doing it and in my case it seems to work fine, but I dont set
the flag anywhere else.

If I dont want to implement a DSR, what would be the best way to implement
this ?


> > I also want a timeout. But not a total timeout value for 
> > the total operation
> > but a timeout based on the interrupt activity. ie if there 
> is no more
> > interrupt for 1/2sec then i want to timeout.
> > 
> > So is ther any function to reset the thread timer. 
> 
> Not exported in C (nor should it be really). You could look 
> in the C++ headers, but there be dragons.

I try to add a cyg_thread_set_delay(thread, delay) function that call
Cyg_Thread::set_timer but I'm not sure it's working... I actually have to
implement a case to test it...

 
> But I would imagine an alternative way to do this is to use 
> two flag bits 
> with cyg_flag_timed_wait() - one bit set on each interrupt, 
> and the other 
> when the operation completes. It's used with CYG_FLAG_WAITMODE_OR.
> 
> Then when the thread wakes up, it checks why it woke up, and 
> if necessary waits again for the operation to complete.

Yes... that would do... the only is that you would have to wake up the
thread for each interrupt in the other case you only wake up once...



-- 
Before posting, please read the FAQ: http://sources.redhat.com/fom/ecos
and search the list archive: http://sources.redhat.com/ml/ecos-discuss



More information about the Ecos-discuss mailing list