Messages in this thread | | | Date | Wed, 2 Jul 2003 11:36:45 -0700 (PDT) | From | Muthian Sivathanu <> | Subject | Re: scheduling with spinlocks held ? |
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Hi,
Is there a version of Ingo Molnar's patch for the 2.4 line kernels ?
thanks, Muthian.
--- Robert Love <rml@tech9.net> wrote: > On Tue, 2003-07-01 at 17:10, Muthian Sivathanu > wrote: > > > Is it safe to assume that the kernel will not > preempt > > a process when its holding a spinlock ? I know > most > > parts of the code make sure they dont yield the > cpu > > when they are holding spinlocks, but I was just > > curious if there is any place that does that. > > Correct. > > > Basically, the context is, I need to change the > > scheduler a bit to implement "perfect nice -19" > > semantics, i.e. give cpu to nice 19 process only > if no > > other normal process is ready to run. I am > wondering > > if there is a possibility of priority inversion if > the > > nice-d process happens to yield the cpu and then > never > > get scheduled because a normal process is spinning > on > > the lock. > > You will hit priority inversion... not with > spinlocks but with > semaphores (and possibly more subtle issues). > > The only safe way to do this safely is to boost the > task's priority out > of the "idle" class when the task is inside the > kernel. > > It is nontrivial to juggle user vs. kernel returns > such as that. Google > for Ingo Molnar's SCHED_BATCH addition to the O(1) > scheduler. > > Robert Love > >
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