On Tue, Jul 17, 2012 at 09:30:52AM +, Emmanuel Dreyfus wrote:
> > You also need to make sure that the kernel knows how many references
> > to C it's been given, so it can drop that many when it calls
> > PUFFS_RECLAIM.
>
> Do you mean I should have the kernel conunting successful lookups,
On Tue, Jul 17, 2012 at 07:48:46AM +, David Holland wrote:
> You also need to make sure that the kernel knows how many references
> to C it's been given, so it can drop that many when it calls
> PUFFS_RECLAIM.
Do you mean I should have the kernel conunting successful lookups,
and send the rec
On Tue, Jul 17, 2012 at 07:38:01AM +, David Holland wrote:
> > > Yeah: don't return copies of things that are basically pointers (in
> > > this case, the cookie) without doing proper usage tracking on them. It
> > > isn't valid to reclaim something that someone else is using;
> >
> > The
On Fri, Jul 13, 2012 at 09:27:46AM +, Emmanuel Dreyfus wrote:
> > Yeah: don't return copies of things that are basically pointers (in
> > this case, the cookie) without doing proper usage tracking on them. It
> > isn't valid to reclaim something that someone else is using;
>
> The proble
Emmanuel Dreyfus wrote:
> When kernel sends a lookup reuest to userland, it causes a node
> to be referenced in userland, but it does not know what vnode
> is associated before it gets the lookup reply. If the vnode
> already existed, it can be reclaimed before the lookup reply,
> there is no way
On Fri, Jul 13, 2012 at 07:58:54AM +, David Holland wrote:
> Yeah: don't return copies of things that are basically pointers (in
> this case, the cookie) without doing proper usage tracking on them. It
> isn't valid to reclaim something that someone else is using;
The problem is that the kern
On Fri, Jul 13, 2012 at 07:30:47AM +0100, David Laight wrote:
> Reference count the cookie somehow?
I already do this [in uncommitted code] and it does not help since
this is a mismatch between kernel and userland refcounts.
> Maybe a 3-way handshake somewhere - so userspace doesn't actually free
On Fri, Jul 13, 2012 at 12:34:20AM +, Emmanuel Dreyfus wrote:
> Understanding how it happens is nice, now the next question is: how
> can I fix it? The only way I can think of is to prevent inactive from
> recycling the vnode if a lookup is in progress anywhere in the filesystem.
> Any bett
On Fri, Jul 13, 2012 at 12:34:20AM +, Emmanuel Dreyfus wrote:
> Hi
>
> I spend days tracking down a race condition in PUFFS lookup. Here is how it
> fails:
>
> - vnode V for file F is associated with cookie C
>
> - enter puffs_vnop_lookup(), looking up file F
> - puffs_vnop_lookup() sends PU
Hi
I spend days tracking down a race condition in PUFFS lookup. Here is how it
fails:
- vnode V for file F is associated with cookie C
- enter puffs_vnop_lookup(), looking up file F
- puffs_vnop_lookup() sends PUFFS_LOOKUP to userland
- userland finds cookie C for F, sends reply to kernel
- some
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