linux-kernel - Re: [PATCH v2 1/2] perf/dwc_pcie: fix the incorrect reference count

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Message-ID: <76dad20a-0180-46a0-9840-6d8444d1749a@linux.alibaba.com>
Date: Fri, 7 Feb 2025 10:19:59 +0800
From: Shuai Xue <xueshuai@...ux.alibaba.com>
To: Yunhui Cui <cuiyunhui@...edance.com>, renyu.zj@...ux.alibaba.com,
 will@...nel.org, mark.rutland@....com, linux-arm-kernel@...ts.infradead.org,
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
 Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v2 1/2] perf/dwc_pcie: fix the incorrect reference count



在 2025/2/5 11:14, Yunhui Cui 写道:
> for_each_pci_dev increments pdev refcount. Call pci_dev_put after access
> to decrement it.
> 
> Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
> ---
>   drivers/perf/dwc_pcie_pmu.c | 42 ++++++++++++++++++++++++++-----------
>   1 file changed, 30 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/perf/dwc_pcie_pmu.c b/drivers/perf/dwc_pcie_pmu.c
> index cccecae9823f..4ac53167d7ab 100644
> --- a/drivers/perf/dwc_pcie_pmu.c
> +++ b/drivers/perf/dwc_pcie_pmu.c
> @@ -553,6 +553,7 @@ static u16 dwc_pcie_des_cap(struct pci_dev *pdev)
>   
>   static void dwc_pcie_unregister_dev(struct dwc_pcie_dev_info *dev_info)
>   {
> +	pci_dev_put(dev_info->pdev);
>   	platform_device_unregister(dev_info->plat_dev);
>   	list_del(&dev_info->dev_node);
>   	kfree(dev_info);
> @@ -572,8 +573,10 @@ static int dwc_pcie_register_dev(struct pci_dev *pdev)
>   		return PTR_ERR(plat_dev);
>   
>   	dev_info = kzalloc(sizeof(*dev_info), GFP_KERNEL);
> -	if (!dev_info)
> +	if (!dev_info) {
> +		platform_device_unregister(plat_dev);
>   		return -ENOMEM;
> +	}
>   
>   	/* Cache platform device to handle pci device hotplug */
>   	dev_info->plat_dev = plat_dev;
> @@ -594,8 +597,11 @@ static int dwc_pcie_pmu_notifier(struct notifier_block *nb,
>   	case BUS_NOTIFY_ADD_DEVICE:
>   		if (!dwc_pcie_des_cap(pdev))
>   			return NOTIFY_DONE;
> -		if (dwc_pcie_register_dev(pdev))
> +		pci_dev_get(pdev);
> +		if (dwc_pcie_register_dev(pdev)) {
> +			pci_dev_put(pdev);
>   			return NOTIFY_BAD;
> +		}
>   		break;
>   	case BUS_NOTIFY_DEL_DEVICE:
>   		dev_info = dwc_pcie_find_dev_info(pdev);
> @@ -730,20 +736,29 @@ static struct platform_driver dwc_pcie_pmu_driver = {
>   	.driver = {.name = "dwc_pcie_pmu",},
>   };
>   
> +static void dwc_pcie_cleanup_devices(void)
> +{
> +	struct dwc_pcie_dev_info *dev_info, *tmp;
> +
> +	list_for_each_entry_safe(dev_info, tmp, &dwc_pcie_dev_info_head, dev_node) {
> +		dwc_pcie_unregister_dev(dev_info);
> +	}
> +}
> +
>   static int __init dwc_pcie_pmu_init(void)
>   {
>   	struct pci_dev *pdev = NULL;
>   	int ret;
>   
>   	for_each_pci_dev(pdev) {
> -		if (!dwc_pcie_des_cap(pdev))
> +		if (!dwc_pcie_des_cap(pdev)) {
> +			pci_dev_put(pdev);

If the pdev has no RAS cap, we do not need to put the device.

> The reference count for @from is
> always decremented if it is not %NULL.

Please see comments from pci_get_device() for more details.

Shuai