Mon, 10 Jul 2000 b m ledvina wrote:
[...]
> So, my question is... am i doing something drastically wrong, or should
> i look for another way of implementing this functionality (i.e. reading
> of the FIFO only when data is present and letting the app do what it
> needs to in the meantime)
Well, that's the easy way, but an application of mine has a serious problem
with it: It's using GGI for rendering (to just about any target), but when it
switches to SCHED_FIFO (Linux/lowlatency) for measuring data, it has to stay
away from GGI, or the system will freeze. (This seems to be a problem with
SCED_FIFO and SCHED_RR in general; my guess is that when communicating with X
and similar servers, short-term deadlock-like situations may occur, which is
normally not a problem, but results in a total user space freeze if one of the
threads involed is a real time thread, and thus won't yield unless it wants to.)
As to the blocking of the entire process; can't help you there, except for a
few suggestions:
* Check that your other thread(s) aren't blocking on the FIFO
accessing thread indirectly. (This can happen easily when
dealing with various mechanisms like semaphores and FIFOs in
between the threads.)
* Check the initialization of your FIFO thread. What does it share
with the parent thread? (The low level Linux API uses a single
call for fork() and the POSIX threads, which lets you pick and
chose as you like among context, stack, memory etc.)
* Check the blocking code in the kernel RTL FIFO driver. (Not that
I suspect anything, but that's about the only other place I could
think of that could possibly cause more than one thread to sleep
on the same kernel call.)
David Olofson
Programmer
Reologica Instruments AB
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