Experimental Physics and
Industrial Control System

"Jun-ichi Odagiri" <[email protected]> · Fri, 13 Jan 2006 09:45:28 +0900

Dear Andrew

>> What I'd like to know is, in other words, if a handler of epicsTimer is
>> allowed to take semaphores in the handler or not.
>> 
>> I guess the statement is TRUE because I have found an example of a
handler
>> to call printf, in "IOC Application Developer's Guide (Chp.19, Section
>> 10.4)".
>
>Yes it is allowed, but you should be aware of the implications of this: 
>If the semaphore blocks, then none of the other epicsTimers that use the 
>same epicsTimerQueue will be executed until the semaphore is released 
>and the callback/notify routine returns.  It is not advisable for a 
>timer on the system shared timer queue to block for any signficant 
>period of time in its callback/notify routine.  The use of printf() and 
>similar functions is fine though because it should not block for any 
>significant period of time.

I got it.
I'm going to use a semaphore just to make a few lines of code atomic in an
epicsTimer handler.
No further blocking call is in the critical section protected by the
semaphore.
So, it should be fine.
Things are now crystal-clear to me.
Thanks a lot for your comments and advice.

Jun-ichi

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System