Re: [PATCH v6 1/2] ftrace: disable preemption when recursion locked

On 2021/10/27 上午10:55, Steven Rostedt wrote:

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

quoted

+/*
+ * 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.

I see, if the problem will be notified anyway then it's fine, v7 on the way.

Regards,
Michael Wang

-- Steve

quoted

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