On Thu, Dec 22, 2011 at 10:59 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > On Wed, 2011-12-21 at 22:48 +0200, raz ben yehuda wrote: >> Vxworks is the use case. And there are plenty of companies with >> vxWorks software and in i believe they will migrate sooner or later to >> PreemptRT. My current company uses old wrapper software that implements >> vxWorks semaphores as system V semaphores. vxWorks semaphores have a priority >> feature which is widely used. >> I will probably change it some time in the future to posix semaphores , but posix >> semaphores are implemented in glibc with futexes and atomic ops and i rather >> mess with kernel and not glibc. funny , but true. glibc is harder. > > Semaphores are a fscking trainwreck for real-time programming. Don't use > them, full stop. If you do, you're doing it wrong, it's really that > simple. > > Use PI mutexes, which are already fully supported in glibc, no extra > patching needed. > > Full NAK for any and all priority fudging for any semaphore > implementation. please correct me if am wrong, " posix semaphores are implemented with pi mutex. ..?" I need a counting semaphore. vxWorks priority/fifo semaphores are different from posix semaphores in that the behaviour is defined on the semaphore and not the thread. Q: what happens if I want one posix semahore to be FIFO and another posix semaphore to be PRIO while both are used by the same thread.should i to change policies each time ? -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
