Re: [RESEND PATCH v2] trace: prevent preemption in perf_ftrace_function_call()

[王贇 <yun.wang@linux.alibaba.com>]

On 2021/10/11 下午4:48, Peter Zijlstra wrote:
> On Mon, Oct 11, 2021 at 10:32:46AM +0200, Peter Zijlstra wrote:
>> diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
>> index a9f9c5714e65..ca12e2d8e060 100644
>> --- a/include/linux/trace_recursion.h
>> +++ b/include/linux/trace_recursion.h
>> @@ -214,7 +214,14 @@ static __always_inline void trace_clear_recursion(int bit)
>>  static __always_inline int ftrace_test_recursion_trylock(unsigned long ip,
>>  							 unsigned long parent_ip)
>>  {
>> -	return trace_test_and_set_recursion(ip, parent_ip, TRACE_FTRACE_START, TRACE_FTRACE_MAX);
>> +	bool ret;
>> +
>> +	preempt_disable_notrace();
>> +	ret = trace_test_and_set_recursion(ip, parent_ip, TRACE_FTRACE_START, TRACE_FTRACE_MAX);
>> +	if (!ret)
>> +		preempt_enable_notrace();
>> +
>> +	return ret;
>>  }
>>  
>>  /**
> 
> Oh, I might've gotten that wrong, I assumed regular trylock semantics,
> but it doesn't look like that's right.

I will use bit instead ret and give some testing :-)

BTW, would you prefer to merge these changes into this patch or maybe send
another patch with your suggested-by?

Regards,
Michael Wang

>