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Message-ID: <tencent_BF745A1543ABB0579DFC20480AA1A4456307@qq.com>
Date: Thu, 21 Mar 2024 10:48:11 +0800
From: linke li <lilinke99@...com>
To: chengming.zhou@...ux.dev
Cc: 42.hyeyoo@...il.com,
akpm@...ux-foundation.org,
cl@...ux.com,
iamjoonsoo.kim@....com,
lilinke99@...com,
linux-kernel@...r.kernel.org,
linux-mm@...ck.org,
penberg@...nel.org,
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roman.gushchin@...ux.dev,
vbabka@...e.cz
Subject: Re: [PATCH] mm/slub: mark racy accesses on slab->slabs
Sorry for a late reply, I just found this because of my bad email client.
> There is another unmarked access of "slab->slabs" in the show_slab_objects(),
> which you can change too.
Yes, I think show_slab_objects() has a similar situation. Should I
consider to submit a V2 patch for this?
> I'm not sure that it's really safe to access "slab->slabs" here without any protection?
> Although it should be no problem in practice, alternative choice maybe putting partial
> slabs count in the kmem_cache_cpu struct.
I think it is ok, because it seems that slab->slabs in slub_percpu_partial
and show_slab_objects() are just used for showing some infomation.
I noticed Paul summarized some of these strategies in access-marking.txt[1]
Quote from it:
"Use of the data_race() Macro
----------------------------
Here are some situations where data_race() should be used instead of
READ_ONCE() and WRITE_ONCE():
1. Data-racy loads from shared variables whose values are used only
for diagnostic purposes.
2. Data-racy reads whose values are checked against marked reload.
3. Reads whose values feed into error-tolerant heuristics.
4. Writes setting values that feed into error-tolerant heuristics.
"
Thanks,
Linke
[1]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/memory-model/Documentation/access-marking.txt
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