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PCI: Avoid unnecessary CPU switch when calling driver .probe() method
If we are already on a CPU local to the device, call the driver .probe() method directly without using work_on_cpu(). This is a workaround for a lockdep warning in the following scenario: pci_call_probe work_on_cpu(cpu, local_pci_probe, ...) driver .probe pci_enable_sriov ... pci_bus_add_device ... pci_call_probe work_on_cpu(cpu, local_pci_probe, ...) It would be better to fix PCI so we don't call VF driver .probe() methods from inside a PF driver .probe() method, but that's a bigger project. [bhelgaas: open bugzilla, rework comments & changelog] Link: https://bugzilla.kernel.org/show_bug.cgi?id=65071 Link: http://lkml.kernel.org/r/CAE9FiQXYQEAZ=0sG6+2OdffBqfLS9MpoN1xviRR9aDbxPxcKxQ@mail.gmail.com Link: http://lkml.kernel.org/r/20130624195942.40795.27292.stgit@ahduyck-cp1.jf.intel.com Tested-by: Yinghai Lu <yinghai@kernel.org> Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Acked-by: Tejun Heo <tj@kernel.org> Acked-by: Yinghai Lu <yinghai@kernel.org>
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1 changed files with 21 additions and 5 deletions
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@ -288,12 +288,27 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
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int error, node;
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struct drv_dev_and_id ddi = { drv, dev, id };
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/* Execute driver initialization on node where the device's
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bus is attached to. This way the driver likely allocates
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its local memory on the right node without any need to
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change it. */
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/*
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* Execute driver initialization on node where the device is
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* attached. This way the driver likely allocates its local memory
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* on the right node.
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*/
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node = dev_to_node(&dev->dev);
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if (node >= 0) {
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/*
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* On NUMA systems, we are likely to call a PF probe function using
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* work_on_cpu(). If that probe calls pci_enable_sriov() (which
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* adds the VF devices via pci_bus_add_device()), we may re-enter
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* this function to call the VF probe function. Calling
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* work_on_cpu() again will cause a lockdep warning. Since VFs are
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* always on the same node as the PF, we can work around this by
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* avoiding work_on_cpu() when we're already on the correct node.
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*
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* Preemption is enabled, so it's theoretically unsafe to use
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* numa_node_id(), but even if we run the probe function on the
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* wrong node, it should be functionally correct.
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*/
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if (node >= 0 && node != numa_node_id()) {
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int cpu;
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get_online_cpus();
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@ -305,6 +320,7 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
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put_online_cpus();
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} else
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error = local_pci_probe(&ddi);
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return error;
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}
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