Messages in this thread | | | From | Nick Piggin <> | Subject | Re: [2.6.27-rc5] inotify_read's ev_mutex vs do_page_fault's mmap_sem... | Date | Wed, 10 Sep 2008 18:03:19 +1000 |
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On Wednesday 10 September 2008 17:57, Peter Zijlstra wrote: > On Wed, 2008-09-10 at 14:07 +1000, Nick Piggin wrote: > > On Wednesday 10 September 2008 07:03, Daniel J Blueman wrote: > > > I observed this locking violation [1] while gnome-panel was loading; > > > this was previously reported at > > > http://uwsg.iu.edu/hypermail/linux/kernel/0806.3/2881.html . > > > > > > Let me know for more information/config/testing. Thanks! > > > > Thanks for the report. I've attached a patch you could test. It compiles > > (and boots a UML here) but I don't think I've actually tested the inotify > > path at all, so it may explode on you. > > > > Peter, this copy_*_user stuff is quite a nightmare... Well actually it > > isn't, if the code is designed with it in mind from the start, but it is > > easy for people to forget it can take mmap_sem and filesystem locks... Is > > there a way to annotate it and say "might take mmap_sem for read" for > > example? So that these LORs will _always_ trigger rather than just once > > in a million times when the reclaim gods frown on us? > > Sure, how about the below - untested - uncompiled, might eat kittens, > etc.. > > Just sprinkle something like: > > might_lock_read(&mm->mmap_sem); > > in the right places.
Ahh, very nice, thanks! I'll give that a try...
> --- > Subject: lockdep: might_lock annotation > > useful to establish a lock dependency in case the actual dependency is > rare or hard to trigger. > > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > --- > diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h > index 331e5f1..0aa657a 100644 > --- a/include/linux/lockdep.h > +++ b/include/linux/lockdep.h > @@ -480,4 +480,22 @@ static inline void print_irqtrace_events(struct > task_struct *curr) # define lock_map_release(l) do { } while (0) > #endif > > +#ifdef CONFIG_PROVE_LOCKING > +# define might_lock(lock) \ > +do { \ > + typecheck(struct lockdep_map *, &(lock)->dep_map); \ > + lock_acquire(&(lock)->dep_map, 0, 0, 0, 2, NULL, _THIS_IP_); \ > + lock_release(&(lock)->dep_map, 0, _THIS_IP_); \ > +} while (0) > +# define might_lock_read(lock) \ > +do { \ > + typecheck(struct lockdep_map *, &(lock)->dep_map); \ > + lock_acquire(&(lock)->dep_map, 0, 0, 1, 2, NULL, _THIS_IP_); \ > + lock_release(&(lock)->dep_map, 0, _THIS_IP_); \ > +} while (0) > +#else > +# define might_lock(lock) do { } while (0) > +# define might_lock_read(lock) do { } while (0) > +#endif > + > #endif /* __LINUX_LOCKDEP_H */
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