linux-kernel - Re: [PATCH 2/5] hwtracing: hisi_ptt: Handle the interrupt in hardirq context

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Message-ID: <20230825122410.00004d6b@Huawei.com>
Date:   Fri, 25 Aug 2023 12:24:10 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Yicong Yang <yangyicong@...wei.com>
CC:     <suzuki.poulose@....com>, <mathieu.poirier@...aro.org>,
        <linux-kernel@...r.kernel.org>,
        <alexander.shishkin@...ux.intel.com>, <helgaas@...nel.org>,
        <linux-pci@...r.kernel.org>, <prime.zeng@...ilicon.com>,
        <linuxarm@...wei.com>, <yangyicong@...ilicon.com>,
        <hejunhao3@...wei.com>
Subject: Re: [PATCH 2/5] hwtracing: hisi_ptt: Handle the interrupt in
 hardirq context

On Wed, 9 Aug 2023 16:18:22 +0800
Yicong Yang <yangyicong@...wei.com> wrote:

> From: Yicong Yang <yangyicong@...ilicon.com>
> 
> Handle the trace interrupt in the hardirq context, make sure the irq
> core won't threaded it by declaring IRQF_NO_THREAD and userspace won't
> balance it by declaring IRQF_NOBALANCING. Otherwise we may violate the
> synchronization requirements of the perf core, referenced to the
> change of arm-ccn PMU commit 0811ef7e2f54 ("bus: arm-ccn: fix PMU interrupt flags").
> 
> In the interrupt handler we mainly doing 2 things:
> - Copy the data from the local DMA buffer to the AUX buffer
> - Commit the data in the AUX buffer
> 
> Signed-off-by: Yicong Yang <yangyicong@...ilicon.com>

Acked-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> ---
>  drivers/hwtracing/ptt/hisi_ptt.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hwtracing/ptt/hisi_ptt.c b/drivers/hwtracing/ptt/hisi_ptt.c
> index 5f0a8e653ae8..89638ed96cf9 100644
> --- a/drivers/hwtracing/ptt/hisi_ptt.c
> +++ b/drivers/hwtracing/ptt/hisi_ptt.c
> @@ -346,9 +346,9 @@ static int hisi_ptt_register_irq(struct hisi_ptt *hisi_ptt)
>  		return ret;
>  
>  	hisi_ptt->trace_irq = pci_irq_vector(pdev, HISI_PTT_TRACE_DMA_IRQ);
> -	ret = devm_request_threaded_irq(&pdev->dev, hisi_ptt->trace_irq,
> -					NULL, hisi_ptt_isr, 0,
> -					DRV_NAME, hisi_ptt);
> +	ret = devm_request_irq(&pdev->dev, hisi_ptt->trace_irq, hisi_ptt_isr,
> +				IRQF_NOBALANCING | IRQF_NO_THREAD, DRV_NAME,
> +				hisi_ptt);
>  	if (ret) {
>  		pci_err(pdev, "failed to request irq %d, ret = %d\n",
>  			hisi_ptt->trace_irq, ret);