On Mon, 2008-07-21 at 21:15 +0200, Andi Kleen wrote: > Peter Zijlstra wrote: > > On Mon, 2008-07-21 at 11:17 +0200, Andi Kleen wrote: > >> Peter Zijlstra wrote: > >>> On Mon, 2008-07-21 at 09:51 +0800, Zhao Yakui wrote: > >>>> On Sat, 2008-07-19 at 11:16 -0700, Daniel Walker wrote: > >>>>> Instead of re-using semaphores for the mutex operation, I've > >>>>> added usage of the kernel mutex for the os mutex implementation. > >>>>> > >>>> What is the advantage that the kernel mutex is used for the ACPI mutex > >>>> implementation instead of using semaphore? > >>>> And it seems that too much ACPICA source code is touched. > >>> You get help from lockdep, and also our goal is to fully eradicate > >>> semaphore usage. > >> Issue is that ACPICA is shared with other OS source code and to replace > >> a major interface like this would mean replacing it for everyone. It > >> might end up with ACPICA just reimplementing a semaphore like wrapper if > >> semaphores really go away, but I don't really see that coming anyways. > > > > Andi, you know better than that. > > Know better than what? Know better than to say we need ugly code in Linux because $SOME_OTHER_OS. > My understanding was that there are a few areas > in the kernel who really use true semaphore semantics and I don't see it > as particularly useful to force them to use something else that doesn't > fit them as well. And there are areas like ACPICA where semaphores are > an useful abstraction because of other consideration (in ACPICA's case > due to portability). Does ACPICA use counting semaphores? If so, you could have used real arguments against his patches, instead of this other-os bull. Also, what is the justification for using counting semaphores? Are we counting hardware slots or is it just generic ACPI braindamage? Clearly this all wasn't extremely clear from the code - otherwise Daniel wouldn't even have done these patches. > Especially now that semaphores are not duplicated per architecture > anymore so actually keeping them around is not that costly. Having them around might give people the idea its a good idea to use them. Not having them around is a good way to discourage that. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
