Experimental Physics and
Industrial Control System

rivers via Core-talk <core-talk at aps.anl.gov> · Sun, 02 Feb 2020 15:54:12 -0000

> Looking at release notes and commits
>   https://github.com/epics-base/epics-base/compare/R7.0.3...R7.0.3.1
> it looks like this could be a side

> Wasn't 1/60 the default tick time on VxWorks? effect of switching
internal timers to monotonic time.

Yes, I discussed both of these in the tech-talk thread.

The Application Developers Guide does not document a minimum value for
the delay time in callbackRequestDelay().  Given that, the existing
behavior should be preserved, which was that 1/60. second did not result
in 0 delay.  I believe that has been the behavior since at least the
beginning of 3.14.

A reasonable expectation for the minimum value of the delay, given that
it is not documented, is that it should be the same as the minimum value
of epicsThreadSleep.  That is documented as follows:

"Sleep for the specified period of time, i.e. sleep without using the cpu.
If delay is >0 then the thread will sleep at least until the next clock tick.
The exact time is determined by the underlying architecture. If delay is
<= 0 then a delay of 0 is requested of the underlying architecture. What
happens is architecture dependent but often it allows other threads of the
same priority to run."

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https://bugs.launchpad.net/bugs/1861612

Title:
  callbackRequestDelay not waiting for 1/60 sec on vxWorks

Status in EPICS Base:
  New

Bug description:
  The problem is documented in this tech-talk thread:
  https://epics.anl.gov/tech-talk/2020/msg00308.php

  In 7.0.3.1, but not in 7.0.3, callbackRequestDelay(1/60) results in
  100% CPU time, most of the time in cbHigh.

  This happens on vxWorks 6.9.4.1 and was first seen with the scaler
  record with multiple types of scaler hardware and device support.

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System