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    SubjectRe: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.43-00
    On Mon, 4 Apr 2005, Zwane Mwaikambo wrote:

    > On Mon, 4 Apr 2005, Steven Rostedt wrote:
    > > On Mon, 2005-04-04 at 22:47 +0200, Ingo Molnar wrote:
    > >
    > > > > Currently my fix is in yield to lower the priority of the task calling
    > > > > yield and raise it after the schedule. This is NOT a proper fix. It's
    > > > > just a hack so I can get by it and test other parts.
    > > >
    > > > yeah, yield() is a quite RT-incompatible concept, which could livelock
    > > > an upstream kernel just as much - if the task in question is SCHED_FIFO.
    > > > Almost all yield() uses should be eliminated from the upstream kernel,
    > > > step by step.
    > >
    > > Now the question is, who will fix it? Preferably the maintainers, but I
    > > don't know how much of a priority this is to them. I don't have the time
    > > now to look at this and understand enough about the code to be able to
    > > make a proper fix, and I'm sure you have other things to do too.
    > I'm sure a lot of the yield() users could be converted to
    > schedule_timeout(), some of the users i saw were for low memory conditions
    > where we want other tasks to make progress and complete so that we a bit
    > more free memory.

    Easy, but damn ugly. Completions are the right answer. The memory system
    needs a queue system where tasks can sleep (with a timeout) until the
    right amount of memory is available instead of half busy-looping.


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