[ECOS] Hard realtime issue in eCos

["Kevin S. Martin" <ksmartin at fnal dot gov>]

I'm running eCos on a i386 target (100MHz 486). My application runs at 
1Khz and lasts for ~500uSec (i.e. it uses 50% of the CPU bandwidth). The 
application code executes (at 1KHz) as a result of a hardware interrupt 
and runs as a ISR (i.e. at interrupt level).

99.999% of the time the interrupt latencies have a range of 20-40uSec 
which is fine and acceptable. However, at a rate of about once every 2-4 
days there is a "glitch". I don't know what causes the "glitch" but when 
it happens my application's interrupt is held off for 2-4mSec :O. This 
totally breaks my realtime signal processing and causes the application 
to "trip".

The only other processing going on in the system (other then kernel 
processing) is the network. The system is on Ethernet. Normal network 
communication to the system does not cause this problem. I have 
exercised the system (via the network) up to the point of the CPU being 
100% utilized with affecting my high priority realtime application.

Is it possible that on rare occasions there is a network "storm" which 
causes many network interrupts, one right after the next, causing my 
applications interrupt not to get handled? If so, how can I see this and 
then of course stop it?

One idea that I had was to run the Ethernet driver in polled mode rather 
then interrupt mode. This would prevent a network "storm" from affecting 
my high priority application. Can this be done?

Is there any other possible cause for this "glitch" that any one can 
think of?

Thanks,
Kevin Martin

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