Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Fri, 16 Nov 2007 17:25:47 -0600

Andrew Johnson wrote:

**************
Modified
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# source files

(6) base-3.14.9/src/libCom/osi/epicsMutex.cpp
    The function epicsMutexLockWithTimeout() is added.

(7) base-3.14.9/src/libCom/osi/epicsMutex.h
    The constant LOG_LAST_OWNER is defined. The function
    epicsMutexLockWithTimeout and epicsMutexOsdLockWithTimeout are
    declared.

I would like to see modifications to libCom/test/epicsMutexTest.cpp to
comprehensively test these changes, checking for all combinations of

simultaneous calls to lock and lock with timeout on the same mutex. I

am not an expert on pthreads and I haven't had a chance to look at the

posix implementation in detail, but it definitely needs to be examined

closely. We will need implementations for RTEMS and Windows as well —

the first should not be a problem, but I don't know anything about

Windows.

(8) base-3.14.9/src/libCom/osi/epicsThread.h
    The function epicsThreadDelete is declared.

As with both Eric and Kay, I have a fundamental problem with adding this

functionality: Deleting a thread leaves the software in an undefined

state; it is not possible to continue operation after doing this since

the deleter has no knowledge of what resources the thread has allocated

or reserved at the moment it was cancelled. This is precisely why the

epicsThread APIs have not supported the ability to delete a thread and

all thread shutdown must be performed by having the thread itself return

to its caller.

(9) base-3.14.9/src/libCom/osi/epicsTime.h
    The function epicsTimeGetTicks is declared.

A 'tick' has no meaning in some operating systems, and could be wildly
different in size.  We removed all references to ticks from the IOC
portable code; why is this needed?

(10) base-3.14.9/src/libCom/osi/os/posix/osdMutex.c
    The structure epicsMutexOSD is extended and the function
    epicsMutexOsdLockWithTimeout is implemented.

(11) base-3.14.9/src/libCom/osi/os/posix/osdThread.c
    The function epicsThreadDelete is implemented.

(12) base-3.14.9/src/libCom/osi/os/posix/osdTime.cpp
    The function epicsTimeGetTicks is implemented.

(13) base-3.14.9/src/libCom/osi/os/vxWorks/iocClock.c
    The function epicsTimeGetTicks is implemented.

(14) base-3.14.9/src/libCom/osi/os/vxWorks/osdMutex.c
    The function epicsMutexOsdLockWithTimeout is implemented.

(15) base-3.14.9/src/libCom/osi/os/vxWorks/osdThread.c
     The function epicsThreadDelete is implemented.

The above changes implement the facilities discussed above for vxWorks
and Posix-compliant OSs.  If we accept the need for them, we will also
need implementations for WIN32 and RTEMS.

**************
Added
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(3) base-3.14.9/src/libCom/osi/os/Linux/osdFindSymbol.c
    Implement the function epicsFindSymbol for Linux.

(4) base-3.14.9/src/libCom/osi/os/posix/osdFindSymbol.c
    Implement the function epicsFindSymbol for posix.

This functionality is not required if suitable function pointers are
provided that the Base code calls at the appropriate place.  It will
not be possible to create an RTEMS implementation of epicsFindSymbol()
until the RTEMS OS incorporates Till Strauman's 'cexp' shell, which
apparently is not likely to happen in the near term.  I do not know
whether it will be possible to implement this on Windows.

- Andrew
--
When a distinguished but elderly scientist states that something is
possible, he is almost certainly right.  When he states that something
is impossible, he is very probably wrong.  -- Arthur C. Clarke

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System