Messages in this thread | | | From | Bjorn Helgaas <> | Date | Tue, 18 Oct 2011 10:49:39 -0600 | Subject | Re: [PATCH 1/8] pci: Make sriov work with hotplug removal |
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On Mon, Oct 17, 2011 at 4:24 PM, Yinghai Lu <yinghai.lu@oracle.com> wrote: > On 10/17/2011 03:12 PM, Bjorn Helgaas wrote: >> >> Maybe this is the best we can do, but it still doesn't seem ideal, and >> it's certainly not obvious when reading the code. It doesn't seem >> right for the driver ->remove() method to be calling >> pci_destroy_dev(). Won't the core data structures be corrupted if a >> defective driver doesn't call pci_disable_sriov()? Seems like we >> could end up with a device that's been physically removed, but still >> has pci_dev structs hanging around. > > i did add some print out in > pci_stop_bus_device > when stop PF, that function is called for those VFs. > > also driver have to call pci_disable_sriov() and that is current design.
Yep. But I don't have to like the current design :) It doesn't seem as robust as it could be.
It took me a long time to puzzle out what was happening here. Here's some possible changelog text that would have saved me a lot of time:
The PCI hot-remove path calls pci_stop_bus_devices() via pci_remove_bus_device().
pci_stop_bus_devices() traverses the bus->devices list (point A below), stopping each device in turn, which calls the driver remove() method. When the device is an SR-IOV PF, the driver calls pci_disable_sriov(), which also uses pci_remove_bus_device() to remove the VF devices from the bus->devices list (point B).
pci_remove_bus_device pci_stop_bus_device pci_stop_bus_devices(subordinate) list_for_each(bus->devices) <-- A pci_stop_bus_device(PF) ... driver->remove pci_disable_sriov ... pci_remove_bus_device(VF) <remove from bus_list> <-- B
At B, we're changing the same list we're iterating through at A, so when the driver remove() method returns, the pci_stop_bus_devices() iterator has a pointer to a list entry that has already been freed.
This patch avoids the problem by building a separate list of all PFs on the bus and traversing that at A instead of the bus->devices list. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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