tracing/urgent: warn in case of ftrace_start_up inbalance

Prevent from further ftrace_start_up inbalances so that we avoid
future nop patching omissions with dynamic ftrace.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index bb60732ade0c..3718d55fb4c3 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1224,6 +1224,13 @@ static void ftrace_shutdown(int command)
                 return;
 
         ftrace_start_up--;
+        /*
+         * Just warn in case of unbalance, no need to kill ftrace, it's not
+         * critical but the ftrace_call callers may be never nopped again after
+         * further ftrace uses.
+         */
+        WARN_ON_ONCE(ftrace_start_up < 0);
+
         if (!ftrace_start_up)
                 command |= FTRACE_DISABLE_CALLS;