Re: [PATCH v2] mm, slub: emit the "free" trace report before freeing memory in kmem_cache_free()

[Yunfeng Ye]

On 2021/11/3 2:37, John Hubbard wrote:
> On 11/2/21 04:43, Yunfeng Ye wrote:
>> After the memory is freed, it can be immediately allocated by other
>> CPUs, before the "free" trace report has been emitted. This causes
>> inaccurate traces.
>>
>> For example, if the following sequence of events occurs:
>>
>>      CPU 0                 CPU 1
>>
>>    (1) alloc xxxxxx
>>    (2) free  xxxxxx
>>                           (3) alloc xxxxxx
>>                           (4) free  xxxxxx
>>
>> Then they will be inaccurately reported via tracing, so that they appear
>> to have happened in this order:
>>
>>      CPU 0                 CPU 1
>>
>>    (1) alloc xxxxxx
>>                           (2) alloc xxxxxx
>>    (3) free  xxxxxx
>>                           (4) free  xxxxxx
>>
>> This makes it look like CPU 1 somehow managed to allocate mmemory that
> 
> 
> I see I created a typo for you, sorry about that: s/mmemory/memory/
> 
> But anyway, the wording looks good now. Please feel free to add:
> 
> Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
> 
Ok, I will fix the typo in the v3 patch.

Thanks.

> 
> thanks,