linux-kernel - Re: [PATCH v16 5/9] PCI/AER: Factor out error reporting from AER

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Date:   Fri, 11 May 2018 14:58:57 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Oza Pawandeep <poza@...eaurora.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dongdong Liu <liudongdong3@...wei.com>,
        Keith Busch <keith.busch@...el.com>, Wei Zhang <wzhang@...com>,
        Sinan Kaya <okaya@...eaurora.org>,
        Timur Tabi <timur@...eaurora.org>
Subject: Re: [PATCH v16 5/9] PCI/AER: Factor out error reporting from AER

On Fri, May 11, 2018 at 06:43:24AM -0400, Oza Pawandeep wrote:
> +void pcie_do_fatal_recovery(struct pci_dev *dev)
> +{
> +	struct pci_dev *udev;
> +	struct pci_bus *parent;
> +	struct pci_dev *pdev, *temp;
> +	pci_ers_result_t result = PCI_ERS_RESULT_RECOVERED;
> +	struct aer_broadcast_data result_data;
> +
> +	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE)
> +		udev = dev;
> +	else
> +		udev = dev->bus->self;
> +
> +	parent = udev->subordinate;
> +	pci_lock_rescan_remove();
> +	list_for_each_entry_safe_reverse(pdev, temp, &parent->devices,
> +				 bus_list) {
> +		pci_dev_get(pdev);
> +		pci_dev_set_disconnected(pdev, NULL);
> +		if (pci_has_subordinate(pdev))
> +			pci_walk_bus(pdev->subordinate,
> +				     pci_dev_set_disconnected, NULL);
> +		pci_stop_and_remove_bus_device(pdev);
> +		pci_dev_put(pdev);
> +	}

Any reason not to simply call

	pci_walk_bus(udev->subordinate, pci_dev_set_disconnected, NULL);

before the list_for_each_entry_safe_reverse() iteration, instead of
calling it for each device on the subordinate bus and for each
device's children?  Should be semantically identical, saves 3 LoC
and saves wasted cycles of acquiring pci_bus_sem over and over again
for each device on the subordinate bus.

Thanks,

Lukas