linux-kernel - Re: ftrace_graph_filter not working correctly since v4.10

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Date:   Thu, 2 Mar 2017 12:49:40 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Todd Brandt <todd.e.brandt@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: ftrace_graph_filter not working correctly since v4.10

On Wed, 1 Mar 2017 22:47:30 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Wed, 1 Mar 2017 22:28:43 -0500
> Steven Rostedt <rostedt@...dmis.org> wrote:
> > 
> > 4.10 is fine. It's what has been merged for 4.11 that's broken. I'm
> > doing a bisect now to see what broke it. Yes, lots of commits touched
> > that code recently.  
> 
> I found the bad commit. I'll have a patch for you to test tomorrow.
> 

Can you test this patch please.

-- Steve

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 2d554a0..1b33a41 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4403,10 +4403,9 @@ static void __init set_ftrace_early_graph(char *buf, int enable)
 	char *func;
 	struct ftrace_hash *hash;
 
-	if (enable)
-		hash = ftrace_graph_hash;
-	else
-		hash = ftrace_graph_notrace_hash;
+	hash = alloc_ftrace_hash(FTRACE_HASH_DEFAULT_BITS);
+	if (WARN_ON(!hash))
+		return;
 
 	while (buf) {
 		func = strsep(&buf, ",");
@@ -4416,6 +4415,11 @@ static void __init set_ftrace_early_graph(char *buf, int enable)
 			printk(KERN_DEBUG "ftrace: function %s not "
 					  "traceable\n", func);
 	}
+
+	if (enable)
+		ftrace_graph_hash = hash;
+	else
+		ftrace_graph_notrace_hash = hash;
 }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */