linux-kernel - Re: [PATCH v2] mm, slub: emit the "free" trace report before freeing memory in kmem_cache

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Date:   Tue, 2 Nov 2021 15:39:16 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Tang Yizhou <tangyizhou@...wei.com>,
        Yunfeng Ye <yeyunfeng@...wei.com>, cl@...ux.com,
        penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     jhubbard@...dia.com, songmuchun@...edance.com, willy@...radead.org,
        wuxu.wu@...wei.com, Hewenliang <hewenliang4@...wei.com>
Subject: Re: [PATCH v2] mm, slub: emit the "free" trace report before freeing
 memory in kmem_cache_free()

On 11/2/21 14:53, Tang Yizhou wrote:
> On 2021/11/2 19:43, Yunfeng Ye wrote:
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -3526,8 +3526,8 @@ void kmem_cache_free(struct kmem_cache *s, void *x)
>>  	s = cache_from_obj(s, x);
>>  	if (!s)
>>  		return;
>> -	slab_free(s, virt_to_head_page(x), x, NULL, 1, _RET_IP_);
>>  	trace_kmem_cache_free(_RET_IP_, x, s->name);
>> +	slab_free(s, virt_to_head_page(x), x, NULL, 1, _RET_IP_);
>>  }
> 
> It seems that kmem_cache_free() in mm/slab.c has the same problem.
> We can fix it. Thanks.

Doh, true. Should go best before the local_irq_save() there.
And also kmem_cache_free() in mm/slob.c.

Interestingly kfree() is already OK in all 3 implementations.

>>  EXPORT_SYMBOL(kmem_cache_free);
>> 
>