Re: Realtime safe signalling?

[Paul Davis <paul linuxaudiosystems com>]

>> no. none of these mechanisms are safe.
>>=20
>> you need to to use some kernel facility (FIFOs are my favorite) to do
>
>And what do you think Glib::Dispatcher::emit() is using?? Right, FIFOs.
>Be sure not to share one dispatcher between several threads though as it
>does some locking.

no locking is acceptable at all for RT usage. My implementation of the
same idea stuffs Slots into a lock-free FIFO, and then writes a single
bytes to the FIFO to wake up the GUI. If you lock, its not RT-safe.

>> this, and even that is not strictly realtime safe (its better if the
>> FIFOs are in a tmpfs file system, for example).
>
>It does not matter in what filesystem (if any -- see pipe(2)) the fifo
>is in, because the inode is always in "pipefs". What does matter is to
>make that fifo non-blocking (see fcntl(2)).

sorry, i was confusing RT-safe IPC with RT-safe intra-process
communication. you're right, if you use pipe(2), the filesystem is
irrelevant. 

--p