Messages in this thread | | | Date | Tue, 5 Apr 2005 01:09:07 +0200 (METDST) | From | Esben Nielsen <> | Subject | Re: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.43-00 |
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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.
Esben
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