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

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

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);
 	}
 }