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Date:   Tue, 26 Oct 2021 22:55:52 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     =?UTF-8?B?546L6LSH?= <yun.wang@linux.alibaba.com>
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Subject: Re: [PATCH v6 1/2] ftrace: disable preemption when recursion locked
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On Wed, 27 Oct 2021 10:34:13 +0800
王贇 <yun.wang@linux.alibaba.com> 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);
>  }