[linux-audio-dev] realtimeness: pthread_cond_signal vs. pipe write

Jussi Laako jussi.laako at pp.inet.fi
Wed Jul 12 17:54:14 UTC 2006

Dave Robillard wrote:
> realtime thread is pretty sketchy...).  Pipes let you communicate
> between processes though - I havn't tried the fancier POSIX interprocess
> stuff yet.

What do you mean by semaphore then, if not sem_*()?
sem_post(3)/sem_wait(3) are defined in POSIX realtime extensions (librt
in glibc). I would recommend _NOT_ to mix these semaphores (or shared
memory, or message queues) with anything from SysV which is usually
veeery far from being realtime safe, from implementation point of view.
IF the implementation happens to be the same in Linux, doesn't mean
that's the case in any other POSIX system.

Of course you can share semaphores between processes because the
semaphores reside within common namespace (see sem_open(3)).

	- Jussi

P.S. There's also nice sem_overview(7) man page nowadays.

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