Hi! > > > > 2) make ACPI take this lock whenever it touches ports not allocated by itself > > > > and release it on function return. > > > > > > This is costly. > > > > TANSTAAFL. You'll need to take some lock, and if you want port emulation > > or per-device-mutex, you'll have to pay the price. > > True, but precisely, I wonder what will perform the best in practice, a > single semaphore that is unconditionally taken by ACPI/AML, or your > finer-grained approach and its many additional tests. I'd say mutexes are not that bad. ... i/o accesses are expensive, anyway, right? > We may be able to workaround the inter-driver exclusion though, if we > use a semaphore initialized to N, have ACPI take N, but other drivers > take just one. This would let ACPI be exclusive with all the other > drivers, but drivers themselves could otherwise run concurrently. That > being said, we do not appear to have the required primitives to take > more than 1 semaphore resource at once at the moment, so we'd need to > do that first. Hmm, nice hack. Yes, driver-driver serialization would be nasty. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
