Em Wed, Nov 28, 2007 at 08:12:24AM -0600, K.R. Foley escreveu:

John Sigler wrote:

quoted

Hello Steven,

Steven Rostedt wrote:

quoted

John Sigler wrote:

quoted

I need to change the priorities of several soft and hard IRQ handlers.

Namely,

o reduce the prio of "softirq-timer" handler to 10

o reduce the prio of IRQ14 and IRQ15 handlers to 20
   (my flash drives do not support DMA BTW...)

o boost the prio of my I/O boards' IRQ handlers to 60
   (there can be 1 or 2 boards, the driver is a kernel module
    which is loaded after the system has booted.)

I've written a short program that calls
   sched_setscheduler(pid, SCHED_FIFO, &param);
with the appropriate pid, which I look up using ps -ef

Look for the program "chrt". It does this for you. This program is
available in all major distributions of Linux.

Thanks for the tip.

For the record, I found schedutils on Robert Love's page:

http://rlove.org/
http://rlove.org/misc/schedutils-1.5.0.tar.gz

However, I had already solved that part of the problem with a
program of my own.

My real problem is: the IRQ handlers for the I/O boards are
only instantiated when the kernel module is inserted. How do
I /reliably/ determine their pid?

What about something like:
chrt -f -p 99 `/sbin/pidof 'IRQ 8'`

If he knows that IRQ 8 is associated with his device, that is ok,
but how to map device -> IRQ in the first place?
 

quoted

e.g. on one system, the IRQ handler for my I/O board is IRQ5
with pid 745. On another system, it's IRQ20 with pid 808.
On a third system they're IRQ20 and IRQ21 with pid 239 and 240.

See?

Perhaps he could use a kernel command line where he would tell that
for the string used in request_irq the kthread priority should be N.

IIRC there was somebody trying to write a patch to support this at some
point in this list...

- Arnaldo