linux-kernel - Re: [PATCH 4.19 092/229] once: add DO_ONCE_SLOW() for sleepable contexts

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Message-ID: <CAMSo37Vt4BMkY1AJTR5yaWPDaJSQQhbj7xhqnVqDo0Q_Sy6ycg@mail.gmail.com>
Date:   Tue, 1 Nov 2022 20:00:03 +0800
From:   Yongqin Liu <yongqin.liu@...aro.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Eric Dumazet <edumazet@...gle.com>, Willy Tarreau <w@....eu>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Benjamin Copeland <ben.copeland@...aro.org>,
        Daniel Díaz <daniel.diaz@...aro.org>
Subject: Re: [PATCH 4.19 092/229] once: add DO_ONCE_SLOW() for sleepable contexts

Hi, Greg

On Tue, 1 Nov 2022 at 14:26, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Tue, Nov 01, 2022 at 02:07:35PM +0800, Yongqin Liu wrote:
> > Hello,
> >
> > As mentioned in the thread for the 5.4 version here[1], it causes a
> > crash for the 4.19 kernel too.
> > Just paste the log here for reference:
>
> Can you try this patch please:
>
>
> diff --git a/include/linux/once.h b/include/linux/once.h
> index bb58e1c3aa03..3a6671d961b9 100644
> --- a/include/linux/once.h
> +++ b/include/linux/once.h
> @@ -64,7 +64,7 @@ void __do_once_slow_done(bool *done, struct static_key_true *once_key,
>  #define DO_ONCE_SLOW(func, ...)                                                     \
>         ({                                                                   \
>                 bool ___ret = false;                                         \
> -               static bool __section(".data.once") ___done = false;         \
> +               static bool __section(.data.once) ___done = false;           \
>                 static DEFINE_STATIC_KEY_TRUE(___once_key);                  \
>                 if (static_branch_unlikely(&___once_key)) {                  \
>                         ___ret = __do_once_slow_start(&___done);             \

This change works, it does not cause kernel panic again after this
change is applied.

-- 
Best Regards,
Yongqin Liu
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