Several RTEMS OSI calls not safe from ISR

[till]

Some OSI calls should be safe to call from an ISR

epicsEventSignal()
epicsThreadResume()

and maybe

epicsThreadGetPriority()

These routines check the return status of the underlying
RTEMS calls and use errlogPrintf() to report failure which
is illegal from ISR context.

[mdavidsaver (mdavidsaver)]

errlogPrintf() contains a short-circuit if it is called from interrupt context. So while an error message won't be informative, I think these functions are safe to call from an ISR.

> if (epicsInterruptIsInterruptContext()) {
> epicsInterruptContextMessage
> ("errlogPrintf called from interrupt level\n");
> return 0;
> }

[Andrew Johnson (anj)]

I wrote this code that outputs the actual errlogPrintf() message when it gets called from an ISR, but I wasn't sure whether it was a good idea to call tvsnPrint() at ISR level so I never applied it. Comments either way?