[Jack-Devel] JACK 2 is not real time safe on posix?

Hello, it is often being said that JACK 2 is real time safe, for example in the JACK faq. I wondered how JACK 2 suspends a thread, so I checked what happens after the JackClient finished CallProcessCallback(): JackClient::CallProcessCallback() -> JackClient::CycleWaitAux() -> JackClient::WaitSync() -> JackGraphManager::SuspendRefNum() -> JackConnectionManager::SuspendRefNum() -> virtual JackSynchro::TimedWait() However, I found only two classes in the `posix' folder that implement this virtual function: * JackPosixSemaphore: uses `sem_timedwait()' to block * JackFifo: uses `read()' to block However, both `sem_timedwait()' and `read()' are syscalls, so they contain context switch, which means they are non realtime. Actually, the JACK documentation warns to use function like these if you pass a process() callback to jack [1]. So how can JACK claim it would be realtime? (No objections, I just don't understand it) Best, Johannes [1] http://jackaudio.org/files/docs/html/group__ClientCallbacks.html#gafb5ec9fb…