I've been trying to find information about the effects of CONFIG_PREEMPT
on real time kernel threads. The description of CONFIG_PREEMPT says
"...allow preemption of user processes that are executing system
calls...". Most of the discussion seems to revolve around the
modification of the locking implementation.
Suppose: I have two or more kernel threads using the SCHED_FIFO policy
and they have differing priorities. Lets pretend the high priority
kthread is doing a down_interruptible() and the low priority kthread is
cheerfully executing. An interrupt fires and does an up() enabling the
high priority kthread.... Heck, lets say there's no interrupt and the
low priority kthread does the up().... Without compiling my kernel with
CONFIG_PREEMPT=y, will the high priority task get scheduled during the
up()? Or will the low priority task run until it yields? In general,
I'm assuming the scheduler will always reschedule on return from
interrupts and after the release of a synchronization primitive?
Miles
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