Re: [PARPORT] Questions with ppdev

From: Michael Reinelt (
Date: Mon Mar 19 2001 - 02:04:54 EST

  • Next message: Miroslav BENES: "[PARPORT] Problems with kernel 2.4.X and EPAT Shuttle HDD driver"

    Philip Blundell wrote:
    > >Yes, it does, but only if you run the process with SCHED_RR or
    > >SCHED_FIFO. And this is dangerous. If the process hangs (maybe because
    > >of a buggy endless loop), wo can't even kill it, because the process
    > >will use up all of your CPU, and you cannot type something (unless you
    > >have a shell running with SCHED_RR and a higher static priority than the
    > >hanging process).
    > Well, you could introduce a new scheduling policy that has the realtime
    > behaviour for nanosleep but behaves like SCHED_OTHER in all other respects.
    > That seems like a better solution than adding wacky stuff to ppdev.

    This would be the way I'd prefer. But will Linus do this? Will someone
    ask him?

    > Or, run as SCHED_OTHER most of the time but promote yourself to SCHED_RR when
    > you are actually doing port I/O. That should remove most of the risk from
    > infinite loops caused by bugs.

    Another possibility. As lcd4linux does port I/O every 100 msec, I don't
    know how this would affect the performance of the whole system and
    especially the scheduler if I chenge scheduling mode all the time.

    bye, Michael

    netWorks       	                                  Vox: +43 316  692396
    Michael Reinelt                                   Fax: +43 316  692343
    Geisslergasse 4					  GSM: +43 676 3079941
    A-8045 Graz, Austria			      e-mail:

    -- To unsubscribe, send mail to: -- -- with the single word "unsubscribe" in the body of the message. --

    This archive was generated by hypermail 2b29 : Mon Mar 19 2001 - 02:54:21 EST