linux-kernel - Re: [PATCH v5 1/5] soc: qcom: rpmh-rsc: Correctly ignore CPU_CLUSTER

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Message-ID: <e8310c51-d7b1-ac88-cd6b-0965804eb754@codeaurora.org>
Date:   Mon, 4 May 2020 10:49:24 +0530
From:   Maulik Shah <mkshah@...eaurora.org>
To:     Douglas Anderson <dianders@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rafael.j.wysocki@...el.com, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     evgreen@...omium.org, mka@...omium.org, swboyd@...omium.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/5] soc: qcom: rpmh-rsc: Correctly ignore
 CPU_CLUSTER_PM notifications

Hi,

On 4/24/2020 10:16 PM, Douglas Anderson wrote:
> Our switch statement doesn't have entries for CPU_CLUSTER_PM_ENTER,
> CPU_CLUSTER_PM_ENTER_FAILED, and CPU_CLUSTER_PM_EXIT and doesn't have
> a default.  This means that we'll try to do a flush in those cases but
> we won't necessarily be the last CPU down.  That's not so ideal since
> our (lack of) locking assumes we're on the last CPU.
>
> Luckily this isn't as big a problem as you'd think since (at least on
> the SoC I tested) we don't get these notifications except on full
> system suspend.  ...and on full system suspend we get them on the last
> CPU down.  That means that the worst problem we hit is flushing twice.
> Still, it's good to make it correct.
>
> Fixes: 985427f997b6 ("soc: qcom: rpmh: Invoke rpmh_flush() for dirty caches")
> Reported-by: Stephen Boyd <swboyd@...omium.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> Reviewed-by: Maulik Shah <mkshah@...eaurora.org>
> Reviewed-by: Stephen Boyd <swboyd@...omium.org>
> ---
>
> Changes in v5:
> - Corrently => Correctly
>
> Changes in v4:
> - ("...Corrently ignore CPU_CLUSTER_PM notifications") split out for v4.
>
> Changes in v3: None
> Changes in v2: None
>
>   drivers/soc/qcom/rpmh-rsc.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
> index a9e15699f55f..3571a99fc839 100644
> --- a/drivers/soc/qcom/rpmh-rsc.c
> +++ b/drivers/soc/qcom/rpmh-rsc.c
> @@ -806,6 +806,8 @@ static int rpmh_rsc_cpu_pm_callback(struct notifier_block *nfb,
>   	case CPU_PM_EXIT:
>   		cpumask_clear_cpu(smp_processor_id(), &drv->cpus_entered_pm);
>   		goto exit;
> +	default:
> +		return NOTIFY_DONE;

I noticed a bug here,

Either need to unlock and return here.

+	default:
+               ret = NOTIFY_DONE;
+		goto exit;

Or

If you move this patch at the end of series, it should will work fine as is.
Since in patch 5 of this series,  pm_lock is removed, so return 
NOTIFY_DONE; do not any unlock.

When i pulled in only first two changes in this series i got spinlock 
recursion during suspend-resume.
Back when i pull in entire series for validation, the issue do not come 
because last patch removes pm_lock.

Thanks,
Maulik
>   	}
>   
>   	ret = rpmh_rsc_ctrlr_is_busy(drv);

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