ftrace: Only update the function code on write to filter files

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.

Cc: stable@kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 7 insertions, 5 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index ee24fa1935ac..666880d051ef 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2413,14 +2413,16 @@ ftrace_regex_release(struct inode *inode, struct file *file, int enable)
                 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;
 }