linux-kernel - RE: ftrace histogram sorting broken on BE architecures

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Message-ID: <4805b40c3e1547f8a26eeac6932f6499@AcuMS.aculab.com>
Date:   Mon, 16 Dec 2019 15:47:12 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Tom Zanussi' <zanussi@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sven Schnelle <svens@...ckframe.org>
CC:     "linux-trace-devel@...r.kernel.org" 
        <linux-trace-devel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: RE: ftrace histogram sorting broken on BE architecures

> From: Tom Zanussi
> Sent: 12 December 2019 19:17
> On Wed, 2019-12-11 at 11:09 -0500, Steven Rostedt wrote:
> > On Wed, 11 Dec 2019 10:35:57 -0500
> > Steven Rostedt <rostedt@...dmis.org> wrote:
> >
> > > > Any thoughts on how to fix this? I'm not sure whether i fully
> > > > understand the
> > > > ftrace maps... ;-)
> > >
> > > Your analysis makes sense. I'll take a deeper look at it.
> >
> > Sven,
> >
> > Does this patch fix it for you?
> >
> > Tom,
> >
> > Correct me if I'm wrong, from what I can tell, all sums and keys are
> > u64 unless they are a string. Thus, I believe this patch should not
> > have any issues.
...
> > --- a/kernel/trace/tracing_map.c
> > +++ b/kernel/trace/tracing_map.c
> > @@ -148,8 +148,8 @@ static int tracing_map_cmp_atomic64(void *val_a,
> > void *val_b)
> >  #define DEFINE_TRACING_MAP_CMP_FN(type) 	\
> >  static int tracing_map_cmp_##type(void *val_a, void *val_b) \
> >  { \
> > -	type a = *(type *)val_a; \
> > -	type b = *(type *)val_b; \
> > +	type a = (type)(*(u64 *)val_a); 	\
> > +	type b = (type)(*(u64 *)val_b); 	\
> > \
> >  	return (a > b) ? 1 : ((a < b) ? -1 : 0); \
> >  }

That looks so horrid/wrong it can't be right on both BE and LE.

	David

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