On Sun, 24 Feb 2002, Matthew Dillon wrote: > Bruce, your sys.dif was *invaluable*! It would have taken me a lot > longer to figure out the interrupt disablement requirement around > the icu_lock, and the statclock and hardclock forwarding issues (which I > got working by the way!).
Thanks. > It turns out that putting the pending masks in the per-cpu area was > the right solution! It made statclock and hardclock forwarding easy > (I can see why you didn't even try in your patch set, doing it with > a global mask would be nearly impossible). In fact, it made everything > unbelievably easy. > ... [This paragraph reordered] > up. One of the best things about this patch set is that it is really > flexible. We should be able to really make interrupts fly. In fact, > it should even be possible for one cpu to steal another cpu's pending > interrupt(s) fairly trivially, without having to resort to IPIs. Good idea. Stealing would be even easier if the mask were global :-). > The second issue is that cpu_switch() does not save/restore the > PSL_I (interrupt disablement mask). I added a PSL word to the PCB > structure to take care of the problem. Without this if you have > a thread switch away while holding interrupts hard-disabled, the > next thread will inherit the hard disablement. I saw the sti's > you added in various places but I figured the best solution was > to simply save/restore the state. The original code didn't have 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. Bruce To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message