On Mon, 6 May 2013 16:50:07 -0700 Colin Cross <[email protected]> wrote:
> CIFS calls wait_event_freezekillable_unsafe with a VFS lock held, > which is unsafe and will cause lockdep warnings when 6aa9707 > "lockdep: check that no locks held at freeze time" is reapplied > (it was reverted in dbf520a). CIFS shouldn't be doing this, but > it has long-running syscalls that must hold a lock but also > shouldn't block suspend. Until CIFS freeze handling is rewritten > to use a signal to exit out of the critical section, add a new > wait_event_freezekillable_unsafe helper that will not run the > lockdep test when 6aa9707 is reapplied, and call it from CIFS. > > In practice the likley result of holding the lock while freezing > is that a second task blocked on the lock will never freeze, > aborting suspend, but it is possible to manufacture a case using > the cgroup freezer, the lock, and the suspend freezer to create > a deadlock. Silencing the lockdep warning here will allow > problems to be found in other drivers that may have a more > serious deadlock risk, and prevent new problems from being added. > > Signed-off-by: Colin Cross <[email protected]> > --- > include/linux/freezer.h | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/include/linux/freezer.h b/include/linux/freezer.h > index 5b31e21c..d3c038e 100644 > --- a/include/linux/freezer.h > +++ b/include/linux/freezer.h > @@ -212,6 +212,16 @@ static inline bool freezer_should_skip(struct > task_struct *p) > __retval; \ > }) > > +/* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */ > +#define wait_event_freezekillable_unsafe(wq, condition) > \ > +({ \ > + int __retval; \ > + freezer_do_not_count(); \ > + __retval = wait_event_killable(wq, (condition)); \ > + freezer_count_unsafe(); \ > + __retval; \ > +}) > + > #define wait_event_freezable(wq, condition) \ > ({ \ > int __retval; \ > @@ -277,6 +287,9 @@ static inline void set_freezable(void) {} > #define wait_event_freezekillable(wq, condition) \ > wait_event_killable(wq, condition) > > +#define wait_event_freezekillable_unsafe(wq, condition) > \ > + wait_event_killable(wq, condition) > + > #endif /* !CONFIG_FREEZER */ > > #endif /* FREEZER_H_INCLUDED */ I think you also need to convert wait_for_response in the cifs code to use this helper. While it's a pretty straightforward change, you should probably cc [email protected] as well. -- Jeff Layton <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
