:> I don't think we want to make sched_lock any more complex then it
:> already is, so at least for the foreseeable future we are not
:> going to be able to actually execute an interrupt handler until
:> the sched_lock is released in (typically) msleep(). I am rather
:
:Well, my kernel has been executing fast interrupt handlers while sched_lock
:is held for almost a year. It's actually less complicated with respect to
:sched_lock but more complicated with respect to fast interrupt handlers.
:
:> annoyed that two levels of procedure have to be called with the
:> sched_lock held (mi_switch() and cpu_switch()), leaving interrupts
:> disabled for a fairly long period of time, but I don't see any way
:> around it right now.
:
:The worst offenders for interrupt latency seemed to be calcru() and/or
:the sched_locking related to fork and/or exit. Latency was many thousand
:instructions (reasonable only on 100+ MIPS machines). sched_locking for
:calcru() is moostly bogus and should be easy to avoid, but not so for
:context switching.
:...
:Bruce
Yah, that's a fairly nasty routine. sched_lock is being used as
an interlock even more then it is being used to cover scheduler
queueing operations. I think the direction I would take would be
to try to address sched_lock's use rather then try to special case
interrupts.
-Matt
Matthew Dillon
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