On Tue, 2021-09-07 at 12:04 +1000, Oliver O'Halloran wrote: > On Mon, Sep 6, 2021 at 7:49 PM Niklas Schnelle <schnelle@xxxxxxxxxxxxx> wrote: > > Patch 3 I already sent separately resulting in the discussion below but without > > a final conclusion. > > > > https://lore.kernel.org/lkml/20210720150145.640727-1-schnelle@xxxxxxxxxxxxx/ > > > > I believe even though there were some doubts about the use of > > pci_dev_is_added() by arch code the existing uses as well as the use in the > > final patch of this series warrant this export. > > The use of pci_dev_is_added() in arch/powerpc was because in the past > pci_bus_add_device() could be called before pci_device_add(). That was > fixed a while ago so It should be safe to remove those calls now. Hmm, ok that confirms Bjorns suspicion and explains how it came to be. I can certainly sent a patch for that. This would then leave only the existing use in s390 which I added because of a dead lock prevention and explained here: https://lore.kernel.org/lkml/87d15d5eead35c9eaa667958d057cf4a81a8bf13.camel@xxxxxxxxxxxxx/ Plus the need to use it in the recovery code of this series. I think in the EEH code the need for a similar check is alleviated by the checks in the beginning of arch/powerpc/kernel/eeh_driver.c:eeh_handle_normal_event() especially eeh_slot_presence_check() which checks presence via the hotplug slot. I guess we could use our own state tracking in a similar way but felt like pci_dev_is_added() is the more logical choice. > > > Patch 4 "PCI: Export pci_dev_lock()" is basically an extension to commit > > e3a9b1212b9d ("PCI: Export pci_dev_trylock() and pci_dev_unlock()") which > > already exported pci_dev_trylock(). In the final patch we make use of > > pci_dev_lock() to wait for any other exclusive uses of the pdev to be finished > > before starting recovery. > > Hmm, I noticed the EEH > (arch/powerpc/kernel/eeh_driver.c:eeh_pe_report_edev()) and the > generic PCIe error recovery code (see > drivers/pci/pcie/err.c:report_error_detected()) only call > device_lock() before entering the driver's error handling callbacks. I > wonder if they should be using pci_dev_lock() instead. The only real > difference is that pci_dev_lock() will also block user space from > accessing the device's config space while error recovery is in > progress which seems sensible enough. I agree that sounds reasonable.
