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 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
> 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.

- Arnaldo