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List:       linux-rt
Subject:    RE: [rtl] user level hungs
From:       MrJ <9405581j () lux ! levels ! unisa ! edu ! au>
Date:       1998-10-22 0:36:12
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I may be way outa line here, but it could be that your users tasks are simply being starved. Someone has already replied saying that there was (or may have been?) a bug in the select() call, but check if the tasks that are hanging are simply not jusrt being starved out of procerss time by some priority level.

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From: 	Assaf Stoler[SMTP:assaf_s@netvision.net.il]
Sent: 	Tuesday, 20 October, 1998 7:13 PM
To: 	rtl@rtlinux.cs.nmt.edu
Subject: 	[rtl] user level hungs

Hi,

I have an annoying bug, - causes user level task hangs.
.
I have a few real-time tasks, and 5 user level tasks working together,
communicating threw both fifos & shared memory.    from time to time the

user level hangs - or, actually, only part of the user level, I made a
test
that i only run one user level task, the ones that use shared memory set

stuck from time to time. - usually work for a few hours to a day or 2,
and
then stuck, while the real time modules still work fine.
I can eliminate the problem by reducing the real-time speed (less
executions per second) , but on high speed (about 200 to 2000 times a
sec,
which is what i need) I have the problem.
in the test, all the user level task was doing, was reading the shared
memory, and echoing some data out of it to the screen , then waiting for
a
fifo with select (the fifo never got data in the test !), select
time-out,
checking the memory again & so on ....
The program seams to be stuck at the select line, but it might be that
it
seams they way only cause the program sits on that line for about 99% of

the time ...
then the user lever stuck, and I do a "ps x" command, the status of the
stuck program is 'R' (running) , and the cpu usage of it (threw top) is
zero.

any ideas will be very appreciated.

Thanks in advance,

Assaf


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