Re: [PATCH 1/2] ftrace: disable preemption on the testing of recursion

[王贇]

On 2021/10/12 下午8:17, Steven Rostedt wrote:
> On Tue, 12 Oct 2021 13:40:08 +0800
> 王贇 <yun.wang@xxxxxxxxxxxxxxxxx> wrote:
> 
>> @@ -52,11 +52,6 @@ static void notrace klp_ftrace_handler(unsigned long ip,
>>  	bit = ftrace_test_recursion_trylock(ip, parent_ip);
>>  	if (WARN_ON_ONCE(bit < 0))
>>  		return;
>> -	/*
>> -	 * A variant of synchronize_rcu() is used to allow patching functions
>> -	 * where RCU is not watching, see klp_synchronize_transition().
>> -	 */
> 
> I have to take a deeper look at this patch set, but do not remove this
> comment, as it explains the protection here, that is not obvious with the
> changes you made.

Will keep that in v2.

Regards,
Michael Wang

> 
> -- Steve
> 
> 
>> -	preempt_disable_notrace();
>>
>>  	func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
>>  				      stack_node);