linux-kernel - [PATCH 3.2 181/185] ftrace: Fix ftrace hash record update with notrace

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Message-ID: <lsq.1388282924.249755651@decadent.org.uk>
Date:	Sun, 29 Dec 2013 03:08:44 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Steven Rostedt" <srostedt@...hat.com>,
	"Steven Rostedt" <rostedt@...dmis.org>
Subject: [PATCH 3.2 181/185] ftrace: Fix ftrace hash record update with
 notrace

3.2.54-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Steven Rostedt <srostedt@...hat.com>

commit c842e975520f8ab09e293cc92f51a1f396251fd5 upstream.

When disabling the "notrace" records, that means we want to trace them.
If the notrace_hash is zero, it means that we want to trace all
records. But to disable a zero notrace_hash means nothing.

The check for the notrace_hash count was incorrect with:

	if (hash && !hash->count)
		return

With the correct comment above it that states that we do nothing
if the notrace_hash has zero count. But !hash also means that
the notrace hash has zero count. I think this was done to
protect against dereferencing NULL. But if !hash is true, then
we go through the following loop without doing a single thing.

Fix it to:

	if (!hash || !hash->count)
		return;

Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/trace/ftrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1358,7 +1358,7 @@ static void __ftrace_hash_rec_update(str
 		 * If the notrace hash has no items,
 		 * then there's nothing to do.
 		 */
-		if (hash && !hash->count)
+		if (!hash || !hash->count)
 			return;
 	}

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