Re: epicsEvent (posix implementation) bug ?

[Andrew Johnson <anj@aps.anl.gov>]

On Friday 28 January 2011 19:57:02 Till Straumann wrote:
> If multiple threads block on the same event then the current
> implementation (posix) may spuriously wake up more than
> one thread as a result of epicsEventSignal().
>
> This is because the underlying pthread_cond_signal()/pthread_cond_wait()
> explicitly have these same semantics.
>
> IMO it would be a good idea to change epicsEventWait and
> epicsEventWaitWithTimeout so that they handle this possible
> case (and yield the same semantics as the RTEMS and vxWorks
> variants).

Could someone add a failing test to libCom/test/epicsEventTest.cpp to try and 
demonstrate this issue please.  I don't have a proper understanding of what 
the issue is yet, but I don't know the pthreads API very well — I'm not 
denying that an issue exists, just trying to understand it.  I'm also 
wondering why the line above the if() that you suggest converting into a 
while() might contain the comment "no need for while since caller must be 
prepared for no work."

- Andrew
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