On Thu, 17 Mar 2011 19:57:02 +0000, Harlan Stenn wrote: > Please see http://support.ntp.org/bin/view/Dev/RefclockShmV2 [...] > I'm curious if we can support both POSIX and SVID SHM from the same > codebase, and use a flag bit or a mode to select which one is used.
OK, looked at it and the bug it references. Comments: 1. one code base is probably impractical (see separate response to Dave Hart's post). 2. What's needed to coordinate driver and shared memory client access is a proper semaphore or mutex, not more modes to avoid doing the job properly. For crying out loud, Dijkstra's semaphore paper is now ca. 46 years old: http://en.wikipedia.org/wiki/Semaphore_(programming) http://www.cs.utexas.edu/users/EWD/transcriptions/EWD01xx/EWD123.html 3. to get nanosecond timestamping on a non-proprietary platform implies use of (POSIX) clock_gettime() or something like it, which uses (POSIX) struct timespec. If one has those, one likely also has POSIX shared memory and POSIX mutexes and semaphores. Mixing POSIX and SVID seems like a bad idea; at some point, the SVID-specific stuff is going to go the way of Lotus-1-2-3 (and I say that as a long time user of genuine UNIX (Registered Trademark) System V). 4. Assuming specific sizes for an integer is a really bad idea... "(64 bits making up the) clockTimeStamp* and receiveTimeStamp* fields" _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
