releases/2.6.33.15/ftrace-only-update-the-function-code-on-write-to-filter-files.patch

From 058e297d34a404caaa5ed277de15698d8dc43000 Mon Sep 17 00:00:00 2001
From: Steven Rostedt <srostedt@redhat.com>
Date: Fri, 29 Apr 2011 22:35:33 -0400
Subject: ftrace: Only update the function code on write to filter files

From: Steven Rostedt <srostedt@redhat.com>

commit 058e297d34a404caaa5ed277de15698d8dc43000 upstream.

If function tracing is enabled, a read of the filter files will
cause the call to stop_machine to update the function trace sites.
It should only call stop_machine on write.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 kernel/trace/ftrace.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2367,14 +2367,16 @@ ftrace_regex_release(struct inode *inode
 		ftrace_match_records(parser->buffer, parser->idx, enable);
 	}
 
-	mutex_lock(&ftrace_lock);
-	if (ftrace_start_up && ftrace_enabled)
-		ftrace_run_update_code(FTRACE_ENABLE_CALLS);
-	mutex_unlock(&ftrace_lock);
-
 	trace_parser_put(parser);
 	kfree(iter);
 
+	if (file->f_mode & FMODE_WRITE) {
+		mutex_lock(&ftrace_lock);
+		if (ftrace_start_up && ftrace_enabled)
+			ftrace_run_update_code(FTRACE_ENABLE_CALLS);
+		mutex_unlock(&ftrace_lock);
+	}
+
 	mutex_unlock(&ftrace_regex_lock);
 	return 0;
 }