Re: [PATCH dwarves] pahole: avoid adding same struct structure to two rb trees

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Mon, Jun 05, 2023 at 03:54:30PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Jun 05, 2023 at 05:39:19PM +0300, Eduard Zingerman escreveu:
> > On Mon, 2023-06-05 at 10:47 -0300, Arnaldo Carvalho de Melo wrote:
> > > Em Fri, Jun 02, 2023 at 09:08:51PM +0300, Eduard Zingerman escreveu:
> > > > On Fri, 2023-06-02 at 15:04 -0300, Arnaldo Carvalho de Melo wrote:
> > > > > Em Fri, Jun 02, 2023 at 04:52:40PM +0300, Eduard Zingerman escreveu:
> > > > > > Right, you are correct.
> > > > > > The 'structures__tree = RB_ROOT' part is still necessary, though.
> > > > > > If you are ok with overall structure of the patch I can resend it w/o bzero().
> > > 
> > > > > Humm, so basically this boils down to the following patch?
> > > 
> > > > > +++ b/pahole.c
> > > > > @@ -674,7 +674,12 @@ static void print_ordered_classes(void)
> > > > >  		__print_ordered_classes(&structures__tree);
> > > > >  	} else {
> > > > >  		struct rb_root resorted = RB_ROOT;
> > > > > -
> > > > > +#ifdef DEBUG_CHECK_LEAKS
> > > > > +		// We'll delete structures from structures__tree, since we're
> > > > > +		// adding them to ther resorted list, better not keep
> > > > > +		// references there.
> > > > > +		structures__tree = RB_ROOT;
> > > > > +#endif
> > >  
> > > > But __structures__delete iterates over structures__tree,
> > > > so it won't delete anything if code like this, right?
> > >  
> > > > >  		resort_classes(&resorted, &structures__list);
> > > > >  		__print_ordered_classes(&resorted);
> > > > >  	}
> > > 
> > > Yeah, I tried to be minimalistic, my version avoids the crash, but
> > > defeats the DEBUG_CHECK_LEAKS purpose :-\
> > > 
> > > How about:
> > > 
> > > diff --git a/pahole.c b/pahole.c
> > > index 6fc4ed6a721b97ab..e843999fde2a8a37 100644
> > > --- a/pahole.c
> > > +++ b/pahole.c
> > > @@ -673,10 +673,10 @@ static void print_ordered_classes(void)
> > >  	if (!need_resort) {
> > >  		__print_ordered_classes(&structures__tree);
> > >  	} else {
> > > -		struct rb_root resorted = RB_ROOT;
> > > +		structures__tree = RB_ROOT;
> > >  
> > > -		resort_classes(&resorted, &structures__list);
> > > -		__print_ordered_classes(&resorted);
> > > +		resort_classes(&structures__tree, &structures__list);
> > > +		__print_ordered_classes(&structures__tree);
> > >  	}
> > >  }
> > >  
> > 
> > That would work, but I still think that there is no need to replicate call

I'm going thru the pile of stuff from before my vacations, can I take
the above as an Acked-by in addition to your Reported-by?

- Arnaldo

> > to __print_ordered_classes, as long as the same list is passed as an argument,
> > e.g.:
> > 
> > @@ -670,14 +671,11 @@ static void resort_classes(struct rb_root *resorted, struct list_head *head)
> >  
> >  static void print_ordered_classes(void)
> >  {
> > -       if (!need_resort) {
> > -               __print_ordered_classes(&structures__tree);
> > -       } else {
> > -               struct rb_root resorted = RB_ROOT;
> > -
> > -               resort_classes(&resorted, &structures__list);
> > -               __print_ordered_classes(&resorted);
> > +       if (need_resort) {
> > +               structures__tree = RB_ROOT;
> > +               resort_classes(&structures__tree, &structures__list);
> >         }
> > +       __print_ordered_classes(&structures__tree);
> >  }
> 
> Right, that can be done as a follow up patch, further simplifying the
> code.
> 
> I'm just trying to have each patch as small as possible.