[RFC][PATCH 4/8] ftrace: Add test for ops against unsafe RCU functions in callback

[Steven Rostedt <rostedt@goodmis.org>]

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From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

When more than one ftrace_ops is registered, the list function is
is used to call all registered functions. It uses the filter and
notrace hashes from the ftrace_ops to determine if the corresponding
callback should be called or not.

Currently, it does not take into account for RCU unsafe functions.
If multiple functions are registered, and an RCU safe callback is
used on a RCU unsafe function, and the RCU unsafe callback says to
trace all functions, it will end up tracing this RCU unsafe function
and still suffer the problems when using RCU when RCU tracing is
off.

Add a test to the multiple ops list function to test if the ops in
question can use an RCU unsafe function or not, and if the function
being traced happens to be an RCU unsafe function.

Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 3761663..c7ef936 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1471,7 +1471,9 @@ ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip, void *regs)
 	if ((ftrace_hash_empty(filter_hash) ||
 	     ftrace_lookup_ip(filter_hash, ip)) &&
 	    (ftrace_hash_empty(notrace_hash) ||
-	     !ftrace_lookup_ip(notrace_hash, ip)))
+	     !ftrace_lookup_ip(notrace_hash, ip)) &&
+	    (ops->flags & FTRACE_OPS_FL_RCU_SAFE ||
+	     !ftrace_lookup_ip(ftrace_unsafe_rcu, ip)))
 		ret = 1;
 	else
 		ret = 0;
-- 
1.7.10.4