help with context switch monitoring

[urimo]

Hello all,
as a part of a school project i am working on monitoring context switches

i'm working on redhat 8.0, kernel version 2.4.18-14
and for some reason i keep getting unclassified reasons which causing context switches from a process to itself
i am trying to determine each context switch, what was the reason that causes it
whether time slice ended, or yielded, or went for waiting or returned from waiting or parameters changed or task ended to task forked or any possible reason

but all the time i find that the only switches that i cannot determine the reason
happens from a process to itself, all this unrecognized switches from process to itself happens only on interactive processes, and sometimes the need_resched flag is on and sometimes is off

what could possibly cause a context switch from a process to itself?!?!
can a returning of a process with a lower (higher by number) priority from waiting cause a context switch?

please help me
thank you,
Uri.

[Mudgen]

You might get more help in the Programming/Scripting forum.

BTW, you're working with a really ancient kernel and version of Red Hat. Is that a requirement of your project?

[urimo]

yes, i know
unfortunately yes this is the version we're required to work with
i am really starting to think that this problem is a bug in linux
maybe if another process wakes up
and tough its priority is not better than the current process
yet a context switch is called
but i'm not sure
what other possible reason can cause this weird context switches
from an interactive process to itself?