Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Kevin Hilman <khilman@baylibre.com>
To:     Brad Harper <bjharper@gmail.com>,
        linux-amlogic@lists.infradead.org, linux-mmc@vger.kernel.org
Cc:     linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] mmc: host: meson-gx-mmc: fix possible deadlock condition for preempt_rt
In-Reply-To: <24a844c3-c2e0-c735-ccb7-83736218b548@gmail.com>
References: <24a844c3-c2e0-c735-ccb7-83736218b548@gmail.com>
Date:   Thu, 24 Sep 2020 10:01:41 -0700
Message-ID: <7hk0wj9ki2.fsf@baylibre.com>
MIME-Version: 1.0
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Precedence: bulk

Hi Brad,

Brad Harper <bjharper@gmail.com> writes:

> Force threaded interrupts for meson_mmc_irq to prevent possible deadlock=
=20
> condition
> during mmc operations when using preempt_rt with 5.9.0-rc3-rt3 patches=20
> on arm64.
>
> Using meson-gx-mmc with an emmc device on Hardkernel Odroid N2+=20
> configured with
> preempt_rt resulted in the soc becoming unresponsive.=C2=A0 With lock=20
> checking enabled
> the below inconsistent lock state was observed during boot.
>
> After some discussions with tglx in IRC #linux-rt the attached patch was=
=20
> suggested
> to remove IRQF_ONESHOT from request_threaded_irq.
> This has been tested and confirmed by me to resolve both the=20
> unresponsive soc and
> the inconsistent lock state warning when using 5.9.0-rc3-rt3 on arm64=20
> Odroid N2+.
>
> Further review and testing is required to ensure there are no adverse=20
> impacts or
> concerns and that is the correct method to resolve the problem.=C2=A0 I w=
ill=20
> continue
> to test on various amlogic devices with both standard mainline low=20
> latency kernel
> and preempt_rt kernel with -rt patches.

This looks right to me, thanks for sending a fix.

For broader testing, I can add this to my testing branch so it gets
booted on a bunch more platform in KernelCI also.

However...

[...]

> Signed-off-by: Brad Harper <bjharper@gmail.com>
> ---
>  =C2=A0drivers/mmc/host/meson-gx-mmc.c | 2 +-
>  =C2=A01 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/meson-gx-mmc.c=20
> b/drivers/mmc/host/meson-gx-mmc.c
> index 08a3b1c05..130ac134d 100644
> --- a/drivers/mmc/host/meson-gx-mmc.c
> +++ b/drivers/mmc/host/meson-gx-mmc.c
> @@ -1139,7 +1139,7 @@ static int meson_mmc_probe(struct platform_device=20
> *pdev)
>  =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0 host->regs + SD_EMMC_IRQ_EN);
>
>  =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ret =3D request_threaded_irq(=
host->irq, meson_mmc_irq,
> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 meson_mmc_irq_thread, I=
RQF_ONESHOT,
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 meson_mmc_irq_thread, 0,
>  =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 dev_name(&pdev->d=
ev), host);
>  =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (ret)
>  =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 goto err_init_clk;

This patch has been mangled by your mailer, so it doesn't apply cleanly.
If you're using the gmail web UI, this is a common problem.

I strongly recommend using git-send-email to send directly via gmail
SMTP.  The git-send-email docs[1] give some examples on how to set this
up.

Kevin

[1] https://git-scm.com/docs/git-send-email#_examples