Kernel 2.2: tq_scheduler functions scheduling and waiting

[Arthur Naseef]

All:

I have been diagnosing kernel panics for over a week and I have
concerns with the use of tq_scheduler for which I was hoping I
could get some assistance.

Is it considered acceptable for functions in the tq_scheduler
task list to call schedule?  Is it acceptable for such functions
to wait on wait queues?  What limitations exist?

As near as I can determine, the TTY driver code makes use of
the tq_scheduler list for such purposes.

In my testing, I am running with 96 TTY devices (talking to a
high-density modem card) and I consistently achieve kernel panics
when the system is under heavy swapping.  I am continuing to
diagnose the problem.  The kernel panics are triggered mostly in
goodness() and del_from_runqueue(), as indicated by ksym_oops and
gdb, and I suspect the run queue is getting corrupted.

In spite of this testing, I believe that I have an argument against
tq_scheduler functions waiting on wait queues, but I have not
thoroughly convinced myself that (a) this was not already known,
and (b) this is already happening in existing kernel code.

Any help is greatly appreciated.

-art

Arthur Naseef

P.S. If this information is availed through existing documentation,
     searches, or other widely available resources, I would greatly
     appreciate references to this material.  All of my searches to
     date have yielded few results and nothing definitive.