From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
To: Mirsad Todorovac <mirsad.todorovac@alu.unizg.hr>
Cc: maple-tree@lists.infradead.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: BUG: maple_tree: KCSAN: data-race in mas_topiary_replace / mtree_range_walk [EXPERIMENTAL PATCH]
Date: Mon, 2 Oct 2023 12:43:10 -0400 [thread overview]
Message-ID: <20231002164310.bi62wfekacfxb3ve@revolver> (raw)
In-Reply-To: <5a30110b-2457-4638-8779-baa33326f6a6@alu.unizg.hr>
* Mirsad Todorovac <mirsad.todorovac@alu.unizg.hr> [231001 17:09]:
...
>
> They say that one patch speaks more than a thousand words.
>
> I am just running this little patch that actually silences all of the KCSAN warnings.
>
> I cannot tell if these reported data races are the actual bugs, but it is possible that
> the Ubuntu 22.04 gcc is doing some funny stuff when optimising. In Prof. McKenney's
> book I've read about the load-tearing and store-tearing. AFAICS, memory barriers should
> prevent load/store reordering, but not the compiler optimisations.
>
> Please find two versions of the patch attached.
>
> While mas->index and pivots[offset] in maple_range_walk can change concurrently,
> I am not smart enough to see whether you expect that in your algorithm or is it a potential
> bug triggered by GCC optimisations and aggressive Ryzen 9 7950X parallelism.
None of this is necessary, for sure.
I will have to look at this when I have more time to investigate. This
will likely not be soon, however.
Thanks,
Liam
next prev parent reply other threads:[~2023-10-02 16:43 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-21 21:01 BUG: maple_tree: KCSAN: data-race in mas_topiary_replace / mtree_range_walk Mirsad Todorovac
2023-09-22 13:51 ` Liam R. Howlett
2023-09-23 7:26 ` Mirsad Todorovac
2023-09-28 19:59 ` Liam R. Howlett
2023-09-30 7:02 ` Mirsad Todorovac
2023-10-01 21:08 ` BUG: maple_tree: KCSAN: data-race in mas_topiary_replace / mtree_range_walk [EXPERIMENTAL PATCH] Mirsad Todorovac
2023-10-02 16:43 ` Liam R. Howlett [this message]
2023-10-02 19:50 ` Mirsad Todorovac
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