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

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Message-ID: <1576082238.2833.8.camel@kernel.org>
Date:   Wed, 11 Dec 2019 10:37:18 -0600
From:   Tom Zanussi <zanussi@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Sven Schnelle <svens@...ckframe.org>
Cc:     linux-trace-devel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: ftrace histogram sorting broken on BE architecures

Hi Steve, Sven,

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.

The sums are u64, but the keys may not be.  I'll take a look and see,
but I'm out today and won't be able to look into it until tomorrow, if
that's ok.

Tom

> 
> -- Steve
> 
> diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
> index 9a1c22310323..9e31bfc818ff 100644
> --- 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);			
> \
>  }