linux-kernel - Re: [PATCH v4 2/5] soc: qcom: rpmh-rsc: We aren't notified of our own failure w/ NOTIFY

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Date:   Thu, 23 Apr 2020 10:18:30 +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:     mka@...omium.org, swboyd@...omium.org, evgreen@...omium.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/5] soc: qcom: rpmh-rsc: We aren't notified of our own
 failure w/ NOTIFY_BAD

Reviewed-by: Maulik Shah <mkshah@...eaurora.org>

Thanks,
Maulik

On 4/23/2020 3:25 AM, Douglas Anderson wrote:
> When a PM Notifier returns NOTIFY_BAD it doesn't get called with
> CPU_PM_ENTER_FAILED.  It only get called for CPU_PM_ENTER_FAILED if
> someone else (further down the notifier chain) returns NOTIFY_BAD.
>
> Handle this case by taking our CPU out of the list of ones that have
> entered PM.  Without this it's possible we could detect that the last
> CPU went down (and we would flush) even if some CPU was alive.  That's
> not good since our flushing routines currently assume they're running
> on the last CPU for mutual exclusion.
>
> Fixes: 985427f997b6 ("soc: qcom: rpmh: Invoke rpmh_flush() for dirty caches")
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>
> Changes in v4:
> - ("...We aren't notified of our own failure...") split out for v4.
>
> Changes in v3: None
> Changes in v2: None
>
>   drivers/soc/qcom/rpmh-rsc.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
> index 3571a99fc839..e540e49fd61c 100644
> --- a/drivers/soc/qcom/rpmh-rsc.c
> +++ b/drivers/soc/qcom/rpmh-rsc.c
> @@ -823,6 +823,10 @@ static int rpmh_rsc_cpu_pm_callback(struct notifier_block *nfb,
>   		ret = NOTIFY_OK;
>   
>   exit:
> +	if (ret == NOTIFY_BAD)
> +		/* We won't be called w/ CPU_PM_ENTER_FAILED */
> +		cpumask_clear_cpu(smp_processor_id(), &drv->cpus_entered_pm);
> +
>   	spin_unlock(&drv->pm_lock);
>   	return ret;
>   }

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