ftrace: Write in missing comment from a very old commit
authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>
Wed, 7 May 2014 19:06:14 +0000 (15:06 -0400)
committerSteven Rostedt <rostedt@goodmis.org>
Wed, 14 May 2014 15:37:27 +0000 (11:37 -0400)
Back in 2011 Commit ed926f9b35cda "ftrace: Use counters to enable
functions to trace" changed the way ftrace accounts for enabled
and disabled traced functions. There was a comment started as:

/*
 *
 */

But never finished. Well, that's rather useless. I probably forgot
to save the file before committing it. And it passed review from all
this time.

Anyway, better late than never. I updated the comment to express what
is happening in that somewhat complex code.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
kernel/trace/ftrace.c

index 2c99d1f7caf1a3299accc4e0d9fe2a4c9591ff30..61f39f8b62e1ed98460cbcdf45f5345f00319535 100644 (file)
@@ -1552,7 +1552,14 @@ static void __ftrace_hash_rec_update(struct ftrace_ops *ops,
                        in_other_hash = !!ftrace_lookup_ip(other_hash, rec->ip);
 
                        /*
+                        * If filter_hash is set, we want to match all functions
+                        * that are in the hash but not in the other hash.
                         *
+                        * If filter_hash is not set, then we are decrementing.
+                        * That means we match anything that is in the hash
+                        * and also in the other_hash. That is, we need to turn
+                        * off functions in the other hash because they are disabled
+                        * by this hash.
                         */
                        if (filter_hash && in_hash && !in_other_hash)
                                match = 1;