On Sun, 24 Feb 2002, Matthew Dillon wrote: > :cpu_switch() certainly needs to do this if it can be called with the > :interrupt enable flag[s] in different states. I need the sti's (actually > :enable_intr()'s because I don't want fast interrupts to be disabled > :during context switches. This works because enabling interrupts is sure > :to be safe, since we might be switching to a thread that will enable > :them. Some sort of lock is needed to prevent interrupts interfering > :with the switch. I think soft-masking them in critical_enter() is > :sufficient in your version too. > > 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. > Eventually (presumably) we will have per-cpu run queues. That combined > with interrupt stealing may resolve the problem for us. I am still > not convinced that making the various *pending* flags globals will > be more efficient, because it introduces significant cache mastership > issues. It might be easier to do this: OK. I don't care about this yet. Bruce To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
