preemption when running in the kernel

From: Frank Cusack
Date: Fri Nov 07 2003 - 17:21:56 EST

(2.4 kernel)

When a process is running in the kernel, can it be pre-empted at
any time? (Unless you explicity disable preemption.) I think not,
because wouldn't it be unsafe to grab a spinlock? Or does grabbing a
spinlock disable preemption. I mean spin_lock(), not spin_lock_irqsave().

Secondly, can multiple processes be in the kernel at the same time? I
think so, that's the reason for the fine grained locks instead of the BKL.
Or do fine grained locks only serve to allow preemption.


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