Re: More linux-2.6.9 module problems

[linux-os]

On Tue, 9 Nov 2004, Mike Waychison wrote:

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> linux-os wrote:
> > I have a memory-test procedure that tests
> > memory on a board, accessed via the PCI bus.
> > There is a lot of RAM and it's bank-switched
> > into some 64k windows so it takes a lot of
> > time to test, about 60 seconds.
> >
> > This is in a module, therefore inside the kernel.
> > When it is invoked via an ioctl() call, the
> > kernel is frozen for the whole test-time. The
> > test procedure does not use any spin-locks nor
> > does it even use any semaphores. It just does a
> > bunch of read/write operations over the PCI/Bus.
> >
> > I thought that I could enable the preemptible-
> > kernel option and the machine would then respond
> > normally. Not so. Even with 4 CPUs, when one
> > ioctl() is busy in the kernel, nothing else
> > happens until its done. Even keyboard activity
> > is gone, no Caps Lock and no Num Lock, no `ping`
> > response over the network. However, the machine
> > comes back to life when the memory-test is done.
> >
> > This is kernel version 2.6.9. Is it possible that
> > somebody left on the BKL when calling a module
> > ioctl() on this version? If not, what do I do
> > to be able to execute a time-consuming procedure
> > from inside the kernel? Do I break it up into
> > sections and execute schedule() periodically
> > (temporary work-around --works)??
>
> The BKL has always been grabbed across ioctls.  Drop the lock when you
> enter your f_op->ioctl call and grab it again open completion.

Hmmm. I get 'scheduling while atomic' screaming across the screen!
There are no atomic operations in my ioctl functions so I don't
know what its complaining about. I think I shouldn't have tried
to do anything with BKL because I (my task) doesn't own it.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.9 on an i686 machine (5537.79 BogoMips).
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