mtxsleep
mtxsleep(id, mtx, flags, wmesg, to)
error = mtxsleep(c, mtx, flags | PINTERLOCKED, c->cv_desc, timo);
int mtxsleep(const volatile void *, struct mtx *, int, const char *, int)
error = mtxsleep(fmp, &fmp->ipc_lock, PCATCH, "ftxc", 0);