>>>>> "Jan" == Jan Hudec <bulb@ucw.cz> writes: >> Having said that, a POSIX binary semaphore (a concrete specification) >> is not equivalent to a POSIX mutex (another concrete specification). Jan> Yes, they are, in the sense that you can use posix binary semaphore (as Jan> only synchronization function) to implement posix mutex iterface and Jan> vice versa. It will probably be less efficient. No they aren't, as POSIX semaphores do not attempt to prevent priority inversion, while POSIX mutexes implement basic priority inheritance and priority ceiling protocols. Jan> Yes, it should. But then message queue is most appropriate since it can Jan> also pass the actual data along. That's what a file descriptor with Jan> appropriately implemented poll is. >> >> It involves copying. Theoretically it is possible to have the read >> system call avoid copying for whole overwriten pages (by exchanging >> page table entries (and flushing TLBs :-( )), but this may work well >> on some systems, work not so well on others and not work AT ALL when >> the source buffer is actually device memory. Jan> No, it won't work, because the read buffer would have to have same Jan> alignment as the data in cache. I do not understand this ? What do you mean ? What won't work ? ~velco -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
