Re: [Dprobes] Re: [ANNOUNCE] DProbes 1.1: proposing a vm_ops- >swapin() abstraction

From: bsuparna@in.ibm.com
Date: Wed Oct 25 2000 - 07:53:03 EST


 Andi,

   Thanks. Then, I'll work it out in more detail and propose it on
linux-mm as you've suggested.
    Maybe I should also try to think of another example where it might be
useful.
    Anything that comes to mind ?

   Regards
   Suparna

  Suparna Bhattacharya
  Systems Software Group, IBM Global Services, India
  E-mail : bsuparna@in.ibm.com
  Phone : 91-80-5267117, Extn : 2525

Andi Kleen <ak@suse.de> on 10/24/2000 07:51:39 PM

Please respond to Andi Kleen <ak@suse.de>

To: Suparna Bhattacharya/India/IBM@IBMIN
cc: ak@suse.de, Richard J Moore/UK/IBM@IBMGB,
      linux-kernel@vger.kernel.org, dprobes@oss.software.ibm.com
Subject: [Dprobes] Re: [ANNOUNCE] DProbes 1.1

Hallo,

On Tue, Oct 24, 2000 at 07:37:08PM +0530, bsuparna@in.ibm.com wrote:
> For (a), your suggestion of a two pass approach is I guess feasible, but
I
> wish there were a simpler way to do it.
> Actually I don't even really like the idea of forcing the swapped out
page
> back in, which we are having to do right now - it would have been nicer
> if there were a swapin() routine in the vma ops that we could have used
for
> on-demand probe insertion, just the way we use inode address space
> readpage() right now for discardable pages, but maybe that's asking for
too
> much :-) [Could vma type based swapin() logic be a useful abstraction in
> general, aside from dprobes ?].

I think it would be. You could propose it on the linux-mm mailing list and
ask Linus what he thinks.

I agree that it would be much nicer to do it this way.

> We don't quite understand (b), though. There is indeed a race due to our
> not holding the page given to us by handle_mm_fault, while we try to
access
> it, and we need to fix that of course, but that doesn't sound exactly
like
> what you mention here. We do have handle_mm_fault being called under the
mm
> semaphore. Could you explain the deadlock situation that you have in mind
?

It does not exist sorry. I was misremembering the lock hierarchy at that
place when I wrote the mail and should have double checked it.

-Andi

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