PCI: Avoid unnecessary CPU switch when calling driver .probe() method (12c3156f) · Commits · 戴 / test

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>

drivers/pci/pci-driver.c

+21 −5

Original line number	Diff line number	Diff line
		@@ -288,12 +288,27 @@ static int pci_call_probe(struct pci_driver drv, struct pci_dev dev,
		int error, node;
		struct drv_dev_and_id ddi = { drv, dev, id };

		/* Execute driver initialization on node where the device's
		bus is attached to. This way the driver likely allocates
		its local memory on the right node without any need to
		change it. */
		/*
		* Execute driver initialization on node where the device is
		* attached. This way the driver likely allocates its local memory
		* on the right node.
		*/
		node = dev_to_node(&dev->dev);
		if (node >= 0) {

		/*
		* On NUMA systems, we are likely to call a PF probe function using
		* work_on_cpu(). If that probe calls pci_enable_sriov() (which
		* adds the VF devices via pci_bus_add_device()), we may re-enter
		* this function to call the VF probe function. Calling
		* work_on_cpu() again will cause a lockdep warning. Since VFs are
		* always on the same node as the PF, we can work around this by
		* avoiding work_on_cpu() when we're already on the correct node.
		*
		* Preemption is enabled, so it's theoretically unsafe to use
		* numa_node_id(), but even if we run the probe function on the
		* wrong node, it should be functionally correct.
		*/
		if (node >= 0 && node != numa_node_id()) {
		int cpu;

		get_online_cpus();
		@@ -305,6 +320,7 @@ static int pci_call_probe(struct pci_driver drv, struct pci_dev dev,
		put_online_cpus();
		} else
		error = local_pci_probe(&ddi);

		return error;
		}

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