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

>

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