Experimental Physics and
Industrial Control System

Andrew Johnson via Core-talk <[email protected]> · Mon, 17 Jun 2019 19:24:36 -0000

I noticed the other day that VxWorks 6.9 added this API:

    STATUS taskWait(TASK_ID taskId, _Vx_ticks_t timeout);

This behaves like pthread_join(), but without copying the thread's exit status to the caller.

Should the epicsThreadJoin() API take a timeout argument? That seems like a useful thing which could be hard or impossible to implement in portable application code, although I haven't looked too closely at how easy it would be to implement for the other OSs (RTEMS looks easy though). Adding this would also require adding a return status so the application knows what happened. If the routine returned a status value we could avoid the need to call cantProceed(). We could provide an epicsThreadMustJoin() API which does the cantProceed() thing...

Shouldn't the C++ class also have a join() method? The destructor acts as one so maybe it isn't essential, but there's no way to provide it with timeout value or get errors back.

I see that the epicsThread class always sets opts.joinable=1 even when the underlying OS defines EPICS_THREAD_CAN_JOIN (0) and only provides an empty epicsThreadJoin() routine. Is that what you implemented in the "epicsThread fix join" commit 149ab118?

Looking at the Posix implementation, a joinable thread that calls epicsThreadJoin(epicsThreadGetIdSelf()) should become unjoinable, but the code doesn't reset the id->joinable flag despite calling pthread_detach(). I didn't check the others for similar issues.

Do you have any test code for this? I just created an implementation for VxWorks 6.9 and later but it may be too simple, so adding some tests to epicsThreadTest.cpp would be helpful.

Will eventually need documentation and a Release Notes entry.

-- 
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System