From: "Steven Rostedt (Red Hat)" <rost...@goodmis.org>
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 <rost...@goodmis.org>
---
kernel/trace/ftrace.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 2c99d1f..61f39f8 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -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;
--
1.8.5.3
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