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

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Date:   Fri, 11 May 2018 21:41:22 +0530
From:   poza@...eaurora.org
To:     Lukas Wunner <lukas@...ner.de>
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 2018-05-11 21:24, Lukas Wunner wrote:
> On Fri, May 11, 2018 at 09:04:36PM +0530, poza@...eaurora.org wrote:
>> On 2018-05-11 18:28, Lukas Wunner wrote:
>> >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.
>> 
>> Well this is borrowed code from DPC driver, hence I thought to keep 
>> the
>> same.
>> but to me it looks like its taking care of PCIe switch where is goes 
>> through
>> all the subordinates, and which could turn out to be more swicthes 
>> down the
>> line, and son on...
>> it goes all the way down to the tree
> 
> ... which is precisely what the one line I suggested above does.
> 
> You don't need to respin for this alone as far as I'm concerned,
> but please post a follow-up refactoring patch.  I have a patch
> in the pipeline which makes the same change in pciehp, hence this
> caught my eye.
> 
> Thanks,
> 
> Lukas

Thanks Lukas, I will keep this in my pipeline as an optimization.
appreciate your input.

Regards,
Oza.