linux-kernel - [PATCH 3/4] ftrace: Narrow down the protected area of graph

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Date:	Mon, 14 Oct 2013 17:24:25 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung.kim@....com>
Subject: [PATCH 3/4] ftrace: Narrow down the protected area of graph_lock

From: Namhyung Kim <namhyung.kim@....com>

It seems that it doesn't need to hold graph_lock during preparation of
the trace_parser.  At least it makes the code a bit simpler IMHO.

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 kernel/trace/ftrace.c | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 0ff3449b4272..26a229ab0c19 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3973,37 +3973,33 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
 		   size_t cnt, loff_t *ppos)
 {
 	struct trace_parser parser;
-	ssize_t read, ret;
+	ssize_t read, ret = 0;
 	struct ftrace_graph_data *fgd = file->private_data;
 
 	if (!cnt)
 		return 0;
 
-	mutex_lock(&graph_lock);
-
-	if (trace_parser_get_init(&parser, FTRACE_BUFF_MAX)) {
-		ret = -ENOMEM;
-		goto out_unlock;
-	}
+	if (trace_parser_get_init(&parser, FTRACE_BUFF_MAX))
+		return -ENOMEM;
 
 	read = trace_get_user(&parser, ubuf, cnt, ppos);
 
 	if (read >= 0 && trace_parser_loaded((&parser))) {
 		parser.buffer[parser.idx] = 0;
 
+		mutex_lock(&graph_lock);
+
 		/* we allow only one expression at a time */
 		ret = ftrace_set_func(fgd->table, fgd->count, fgd->size,
 				      parser.buffer);
-		if (ret)
-			goto out_free;
+
+		mutex_unlock(&graph_lock);
 	}
 
-	ret = read;
+	if (!ret)
+		ret = read;
 
-out_free:
 	trace_parser_put(&parser);
-out_unlock:
-	mutex_unlock(&graph_lock);
 
 	return ret;
 }
-- 
1.7.11.7

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