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Date: Thu, 20 Sep 2012 18:51:04 -0700 From: Yinghai Lu <yinghai@...nel.org> To: Bjorn Helgaas <bhelgaas@...gle.com> Cc: Jiang Liu <liuj97@...il.com>, Jiang Liu <jiang.liu@...wei.com>, Don Dutile <ddutile@...hat.com>, Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>, Yijing Wang <wangyijing@...wei.com>, linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org Subject: Re: [PATCH 4/5] PCI/IOV: simplify code by hotplug safe pci_get_domain_bus_and_slot() On Thu, Sep 20, 2012 at 4:59 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote: > On Thu, Sep 20, 2012 at 2:38 PM, Yinghai Lu <yinghai@...nel.org> wrote: >> in that case, VFs are stopped before PF, so they are not in device >> tree anymore. >> so pci_get_domain_bus_and_slot will not find those VFs. >> >> So the reference to PF is not released. Also vit_bus may not be released too. >> >> So you have to rework >> pci_get_domain_bus_and_slot to make it work on pci devices get stopped only. >> >> or just drop this from the tree. > > pci_find_bus() is a broken interface (because there's no reference > counting or safety with respect to hot-plug), and if the design > depends on it, that means the design is broken, too. I don't think > reworking pci_get_domain_bus_and_slot() is the right answer. > > It's not clear to me why we need the split between stopping and > removing devices. That split leads to these zombie devices that have > been stopped and are no longer findable by bus_find_device() (which is > used by pci_get_domain_bus_and_slot()), but still "exist" in some > fashion until they're removed. It's unreasonable for random PCI and > driver code to have to worry about that zombie state. That is not zombie state. that is driver unloaded, and not in /sys, /proc. that pci device only can be found under bus->devices. just like we have pci_device_add and pci_bus_add_device or acpi add and acpi start. Splitting stop and remove should be more clean than mixing stop and remove. > > I'll revert this patch for now to fix the regression. Of course, that > means we will still have the old problem of using the unsafe > pci_find_bus(). > >> BTW, Bjorn, >> for the similar reason, you need to apply >> http://git.kernel.org/?p=linux/kernel/git/yinghai/linux-yinghai.git;a=commitdiff;h=e5a50aa3dfca1331c7c783412b1524bea06d2752 >> ... >> the reason is: >> >> We stop all VFs at first , stop PF >> before we stop PF, we can not remove VFs, >> >> otherwise virtfn_remove does not work properly to remove reference and >> virtfn bus while can not find vf. > > I'll apply this one, too, for now. I put them both on the > pci/yinghai-revert-pci_find_bus-and-remove-cleanup branch. Let me > know if that's not what you expected. Yes, they are good. > > I'm not happy about either reverting Jiang's patch or splitting > stop/remove again. It complicates the design and the code. I'll > apply them because they're regressions, and we don't have time for > redesign before 3.7. But I encourage you to think about how to do > this more cleanly. That will need to redesign sriov implementation. Also that pci root bus add/start, stop/remove will need special sequence to make ioapic and dmar to be started early before normal pci device drivers and stopped after normal pci device drivers. -Yinghai -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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