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Re: [PATCH v5 10/11] PCI: Replace pci_dev::driver usage by pci_dev::dev.driver

On 29/09/2021 17:44, Andrew Donnellan wrote:
On 29/9/21 11:43 pm, Uwe Kleine-König wrote:> I'm not a huge fan either, I used it to keep the control flow as is and
without introducing several calls to to_pci_driver.

The whole code looks as follows:

    list_for_each_entry(afu_dev, &afu->phb->bus->devices, bus_list) {
        struct pci_driver *afu_drv;
        if (afu_dev->dev.driver &&
            (afu_drv = to_pci_driver(afu_dev->dev.driver))->err_handler &&

Without assignment in the if it could look as follows:

    list_for_each_entry(afu_dev, &afu->phb->bus->devices, bus_list) {
        struct pci_driver *afu_drv;

        if (!afu_dev->dev.driver)

        afu_drv = to_pci_driver(afu_dev->dev.driver));

        if (afu_drv->err_handler && afu_drv->err_handler->resume)

Fine for me.

This looks fine.

As an aside while writing my email I discovered the existence of container_of_safe(), a version of container_of() that handles the null and err ptr cases... if to_pci_driver() used that, the null check in the caller could be moved until after the to_pci_driver() call which would be neater.

But then, grep tells me that container_of_safe() is used precisely zero times in the entire tree. Interesting.

(Sidenote: What happens if the device is unbound directly after the
check for afu_dev->dev.driver? This is a problem the old code had, too
(assuming it is a real problem, didn't check deeply).)

Looking at any of the cxl PCI error handling paths brings back nightmares from a few years ago... Fred: I wonder if we need to add a lock here?

Yes, it's indeed a potential issue, there's nothing to prevent the afu driver to unbind during that window. Sigh..




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