On Monday, November 21, 2016 9:57:51 AM CET Linus Torvalds wrote: > > - semaphores are "old-fashioned mutexes". A mutex is better than a > semaphore, but a semaphore is better than just about all the other > alternatives. There's nothing _wrong_ with using a semaphore per se. > > In this case, either use a semaphore or a mutex. If you are doing > mutual exclusion, those are really the only two acceptable sleeping > models. The main problem with semaphores is that they are slowly spreading into areas that really should be mutexes or completions. A couple of years ago, we had only around 30 semaphores left in the kernel and while a lot of those have been removed in the meantime, over 100 new ones have come in, the majority of them in the category that can be trivially converted to a mutex or semaphore. This in turn is not much of a problem, except to a certain degree for preempt-rt users. I suggested to Binoy that he could look into replacing the existing semaphores one subsystem at a time under the assumption that we could find a relatively easy alternative for every one of them and then remove the implementation completely. Christoph's suggestion is probably more productive here: let's remove the ones that are obviously wrong or inferior, and only once they have been taken care of we can look into whether it's worth doing something about the rest or not. Arnd -- To unsubscribe from this list: send the line "unsubscribe target-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
