On Wed, 27 Oct 2021 10:34:13 +0800
王贇 [off-list ref] wrote:

+/*
+ * Preemption will be enabled (if it was previously enabled).
+ */
 static __always_inline void trace_clear_recursion(int bit)
 {
+	WARN_ON_ONCE(bit < 0);

Can you send a v7 without the WARN_ON.

This is an extremely hot path, and this will cause noticeable overhead.

If something were to call this with bit < 0, then it would crash and
burn rather quickly.

-- Steve

+
+	preempt_enable_notrace();
 	barrier();
 	trace_recursion_clear(bit);
 }