Re: [PATCH v8 00/14] lockdep: Implement crossrelease feature

Boqun Feng
2017-08-17T08:03:52Z

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On Thu, Aug 17, 2017 at 09:48:11AM +0200, Ingo Molnar wrote:
>
> * Boqun Feng <boqun.feng@gmail.com> wrote:
>
> > --- a/kernel/workqueue.c
> > +++ b/kernel/workqueue.c
> > @@ -2431,6 +2431,27 @@ struct wq_barrier {
> > struct task_struct *task; /* purely informational */
> > };
> >
> > +#ifdef CONFIG_LOCKDEP_COMPLETE
> > +# define INIT_WQ_BARRIER_ONSTACK(barr, func, target) \
> > +do { \
> > + INIT_WORK_ONSTACK(&(barr)->work, func); \
> > + __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&(barr)->work)); \
> > + lockdep_init_map_crosslock((struct lockdep_map *)&(barr)->done.map, \
> > + "(complete)" #barr, \
> > + (target)->lockdep_map.key, 1); \
> > + __init_completion(&barr->done); \
> > + barr->task = current; \
> > +} while (0)
> > +#else
> > +# define INIT_WQ_BARRIER_ONSTACK(barr, func, target) \
> > +do { \
> > + INIT_WORK_ONSTACK(&(barr)->work, func); \
> > + __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&(barr)->work)); \
> > + init_completion(&barr->done); \
> > + barr->task = current; \
> > +} while (0)
> > +#endif
>
> Is there any progress with this bug? This false positive warning regression is
> blocking the locking tree.
>

I have been trying to reproduce the false positive on my machine, but
haven't succeeded. ;-( Have you tried this?

But I have been using this patch for a day and haven't shoot my foot
yet.

> BTW., I don't think the #ifdef is necessary: lockdep_init_map_crosslock should map
> to nothing when lockdep is disabled, right?

IIUC, lockdep_init_map_crosslock is only defined when
CONFIG_LOCKDEP_CROSSRELEASE=y, moreover, completion::map, which used as
the parameter of lockdep_init_map_crosslock(), is only defined when
CONFIG_LOCKDEP_COMPLETE=y. So the #ifdef is necessary, but maybe we can
clean this thing up in the future.

I will send a proper patch, so the thing could move forwards. Just a
minute ;-)

Regards,
Boqun

>
> Thanks,
>
> Ingo

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