Re: [PATCH v7 06/16] lockdep: Detect and handle hist_lock ring buffer overwrite

[Byungchul Park]

On Thu, Jul 13, 2017 at 08:23:33PM +0900, Byungchul Park wrote:
> On Thu, Jul 13, 2017 at 8:12 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > On Thu, Jul 13, 2017 at 12:29:05PM +0200, Peter Zijlstra wrote:
> >> On Thu, Jul 13, 2017 at 07:09:53PM +0900, Byungchul Park wrote:
> >> > On Thu, Jul 13, 2017 at 11:50:52AM +0200, Peter Zijlstra wrote:
> >> > >   wait_for_completion(&C);
> >> > >     atomic_inc_return();
> >> > >
> >> > >                                   mutex_lock(A1);
> >> > >                                   mutex_unlock(A1);
> >> > >
> >> > >
> >> > >                                   <IRQ>
> >> > >                                     spin_lock(B1);
> >> > >                                     spin_unlock(B1);
> >> > >
> >> > >                                     ...
> >> > >
> >> > >                                     spin_lock(B64);
> >> > >                                     spin_unlock(B64);
> >> > >                                   </IRQ>
> >> > >
> >> > >
> >
> > Also consider the alternative:
> >
> >                                         <IRQ>
> >                                           spin_lock(D);
> >                                           spin_unlock(D);
> >
> >                                           complete(&C);
> >                                         </IRQ>
> >
> > in which case the context test will also not work.
> 
> Context tests are done on xhlock with the release context, _not_
> acquisition context. For example, spin_lock(D) and complete(&C) are
> in the same context, so the test would pass in this example.

Something wrong?