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

From: 王贇 <[email-masked]>
Date: Wed, 27 Oct 2021 11:09:29 +0800

On 2021/10/27 上午10:55, Steven Rostedt wrote:
> On Wed, 27 Oct 2021 10:34:13 +0800
> 王贇 <[email-masked]> 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.

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

Regards,
Michael Wang

> 
> -- Steve
> 
> 
>> +
>> +	preempt_enable_notrace();
>>  	barrier();
>>  	trace_recursion_clear(bit);
>>  }