On Fri Sep 17 17:13:40 EDT 2010, [email protected] wrote:
> On Thu, Sep 16, 2010 at 11:02 PM, erik quanstrom <[email protected]>
> wrote:
> > i have these processes all deadlocked. 8.out
> > is serving /n/mntpt.
> >
> > xxx 11921346 0:00 0:00 436K Create 8.out
> > xxx 11921785 0:00 0:00 24K Open cat /n/mntpt/sos
> > xxx 11921786 0:00 0:00 24K Unmount unmount /n/mntpt
> > xxx 11921787 0:00 0:00 44K Pwrite echo x y
>
> tell us why it's interesting. it looks like 8.out can see
> itself so you've got a bad loop.
on second thought, i'm not sure i fully understand why
not forking the namespace should result in a deadlock.
8.out is opening /dev/sdC0/part OTRUNC
cat is opening /n/mntpt/sos
unmount is opening /n/mntpt
so 8.out isn't waiting for itself.
it seems that any one of the three could resonably
finish, but they deadlock. but the problem is
have want
11921346 rlock(&pg->ns)
11921785 rlock(&mh->lock);
11921786 wlock(&pg->ns) wlock(&m->lock);
rlock(&mh->lock) [walk]
the locks for pg->ns mh->lock and m->lock aren't nested.
it would seem if they were, we would get a winner and all three
operations would complete (or fail). so, why can't the locks
be nested? and why does this have to deadlock? what am i missing?
- erik
