Re: [PATCH v2] perf: fix double free at function perf_hpp__reset_output_field

[Jiri Olsa <jolsa@redhat.com>]

On Tue, Apr 11, 2017 at 06:13:17PM +0800, Du, Changbin wrote:
> > > >  
> > > yes, this is an option. But for safety, I sugguest do not rely on list_del_init.
> > > No rule rather than create one.
> > > 
> > > But anyway, both are ok for me. What's your options?
> > 
> > hum, also I dont think we need to touch that bit at all
> > if we are going to remove it right away.. how about the
> > change below?
> > 
> > jirka
> > 
> > 
> > ---
> > diff --git a/tools/perf/ui/hist.c b/tools/perf/ui/hist.c
> > index 5d632dca672a..0ee7db43dd7d 100644
> > --- a/tools/perf/ui/hist.c
> > +++ b/tools/perf/ui/hist.c
> > @@ -613,15 +613,15 @@ void perf_hpp__reset_output_field(struct perf_hpp_list *list)
> >  
> >  	/* reset output fields */
> >  	perf_hpp_list__for_each_format_safe(list, fmt, tmp) {
> > -		list_del_init(&fmt->list);
> > -		list_del_init(&fmt->sort_list);
> > +		list_del(&fmt->list);
> > +		/* Remove the fmt from next loop processing. */
> > +		list_del(&fmt->sort_list);
> >  		fmt_free(fmt);
> What if the fmt is not linked to sort_list? I see it is possible (please
> checking perf_hpp__setup_output_field()). I am not sure if we really has
> sunch case currently, just concern :)

if it's not linked to sort_list, then sort_list is initialized
and list_del should do no harm

jirka