scheduling with spinlocks held ?

[Muthian Sivathanu <muthian_s@yahoo.com>]

Hi,

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.

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.

thanks for any input,
Muthian.

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