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SubjectRe: [PATCH] mm, slub: place the trace before freeing memory in kmem_cache_free()
On Sat, Oct 30, 2021 at 6:12 PM Yunfeng Ye <yeyunfeng@huawei.com> wrote:
>
> After the memory is freed, it may be allocated by other CPUs and has
> been recorded by trace. So the timing sequence of the memory tracing is
> inaccurate.
>
> For example, we expect the following timing sequeuce:
>
> CPU 0 CPU 1
>
> (1) alloc xxxxxx
> (2) free xxxxxx
> (3) alloc xxxxxx
> (4) free xxxxxx
>
> However, the following timing sequence may occur:
>
> CPU 0 CPU 1
>
> (1) alloc xxxxxx
> (2) alloc xxxxxx
> (3) free xxxxxx
> (4) free xxxxxx
>
> So place the trace before freeing memory in kmem_cache_free().

Could you tell me what problem you have encountered
here?

Thanks.

>
> Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
> ---
> mm/slub.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 432145d7b4ec..427e62034c3f 100644
> --- 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_);
> }
> EXPORT_SYMBOL(kmem_cache_free);
>
> --
> 2.27.0

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