On Thu, Jan 25, 2007 at 10:30:56PM -0800, Andrew Morton wrote:
> On Thu, 25 Jan 2007 23:26:59 -0600
> "Serge E. Hallyn" <[email protected]> wrote:
>
> > Fix exit race by splitting the nsproxy putting into two pieces.
> > First piece reduces the nsproxy refcount. If we dropped the last
> > reference, then it puts the mnt_ns, and returns the nsproxy as a
> > hint to the caller. Else it returns NULL. The second piece of
> > exiting task namespaces sets tsk->nsproxy to NULL, and drops the
> > references to other namespaces and frees the nsproxy only if an
> > nsproxy was passed in.
> >
> > A little awkward and should probably be reworked, but hopefully
> > it fixes the NFS oops.
>
> I'm a bit worried about jamming something like this into 2.6.20.
> Could the usual culprits please review this carefully with
> some urgency?
okay, after integrating this into two Linux-VServer
branches and some testing, I can confirm that it
_seems_ to fix the nfs and related issues, but still,
I do not like it :)
here my issues with this approach:
- the code is quite hard to read and can easily
lead to unexpected issues when spaces are
manipulated
- it breaks the basic get/put refcounting for
nsproxy references outside the task struct
i.e. we had to add a vs_put_nsproxy() which
does what the put_nsproxy() did before, to
keep and handle a reference to the nsproxy
from the context structure
- the following scenario might become a problem
for future spaces (especially the pid space?)
A B
exit_task_namespaces_early()
exit_task_namespaces_early()
exit_notify()
exit_task_namespaces()
---------------------------------------------------
exit_notify()
exit_task_namespaces()
note: I still consider it the best available fix
for this issues, especially as 2.6.20 is in a
late rc stage ... but IMHO the nfs threads should
be modified to handle the nsproxy disposal properly
> And Daniel, if you can find time to runtime test it please?
he did, looks like it works fine with vanilla too
(even when stressing the described cornercase)
best,
Herbert
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