On Tue, Jun 20, 2000 at 11:30:39AM -0400, Stephen D. Cohen wrote:
> Victor Et. Al.,
>
> You recently wrote:
>
> > 1. Saving fp state is _slow_ so you don't need it in an ISR
> > -- there is no performance loss
> > in having the ISR hand over work to a thread.
>
> I have been trying to figure out how to do this for some time.
> Would you please provide a code fragment or clear explanation of how to have
> an ISR cause a thread to become computable?
There are several methods. The simplest is to have a thread suspend itself
and then have the ISR send a signal
thread:
isr_ran = 0;
do something
thread_to_wakeup = pthread_self();
rtl_no_interrupts(flag); /* make sure I don't miss the
wakeup */
if(!wakeup_sent)rtl_suspend_np(pthread_self());
/* hey the ISR woke me up */
do something else
ISR_catch_interrupt:
if(thread_to_wakeup)pthread_kill(thread_to_wakeup,RTL_SIG_WAKEUP);
isr_ran = 1;
>
> I thought it would be correct to simply have the thread sleep until
> it gets woken up by the ISR, but I am told that this will cause the thread
> to run in the ISR context. That is, obviously, not what we want. I want to
Only if you do a pthread_wakeup_np(thread) of a higher priority
thread.
> get in and out of ISR context just as quickly as possible, but cause another
> thread to become computable (a high priority hardware handler responding to
> the interrupt, for example).
>
> Any suggestions?
>
> Confusedly Yours,
>
> Steve
>
> P.S. ->
> > 3. Rare workarounds are better than rarely used features.
> > Keeping the API simple is
> > critical.
>
> I could not agree more.
You are, I see, a man of taste and perception.
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