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

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Date:   Wed, 11 Dec 2019 11:09:59 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Sven Schnelle <svens@...ckframe.org>
Cc:     linux-trace-devel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Tom Zanussi <zanussi@...nel.org>
Subject: Re: ftrace histogram sorting broken on BE architecures

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.

-- 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);			\
 }