30 Nov
2015
30 Nov
'15
6:27 a.m.
On 11/30/2015 12:11 PM, Xavier Mendez wrote:
Hello,
I'm wondering whether it's safe to do non-blocking reads or writes from
inside the process callback.
From what I've seen, non-blocking I/O doesn't cause the process to go
into blocked state, and the realtime scheduler should not switch to
another process. But the documentation doesn't seem to allow them:
On which platform?
The short answer is:
"If you don’t know how long it will take, don't do it." [1]
All i/o involve syscalls, and then it depends what the kernel does for
the specific system call(s). Asynchronous I/O usually involves signals
at some point which makes it not safe to use. Some implementation also
involve mutexes to avoid resource conflicts. You'll have to check the
standard-lib and kernel source for the system that you target.
All moot anyway. Proper software needs to do error-handling and doing
that in a rt-callback is out of the question. So you need a non-realtime
thread anyway and if you have that you can directly do i/o there.
anyway, using a ringbuffer to decouple i/o is trivial: e.g.
https://github.com/jackaudio/example-clients/blob/master/capture_client.c
best,
robin
[1]
http://www.rossbencina.com/code/real-time-audio-programming-101-time-waits-…
[...] it cannot call functions that might block
for a long time. This
includes all I/O functions (disk, TTY, network), [...]
So, is it safe to use non-blocking I/O in the process callback?