On Mon, Nov 18, 2013 at 10:14 AM, Bjorn Helgaas [off-list ref] wrote:
quoted
A bit of comment here would be nice but yeah I think this should work.
Can you please also queue the revert of c2fda509667b ("workqueue:
allow work_on_cpu() to be called recursively") after this patch?
Please feel free to add my acked-by.
OK, below are the two patches (Alex's fix + the revert) I propose to
merge. Unless there are objections, I'll ask Linus to pull these
before v3.13-rc1.
commit 84f23f99b507c2c9247f47d3db0f71a3fd65e3a3
Author: Alexander Duyck [off-list ref]
Date: Mon Nov 18 10:59:59 2013 -0700
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: disable preemption, open bugzilla, rework comments & changelog]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=65071
Link: http://lkml.kernel.org/r/CAE9FiQXYQEAZ=0sG6+2OdffBqfLS9MpoN1xviRR9aDbxPxcKxQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org
Link: http://lkml.kernel.org/r/20130624195942.40795.27292.stgit-+uVpp3jiz/Q1YPczIWDRvLvm/XP+8Wra@public.gmane.org
Signed-off-by: Alexander Duyck [off-list ref]
Signed-off-by: Bjorn Helgaas [off-list ref]
Acked-by: Tejun Heo [off-list ref]
Tested-by: Yinghai Lu <redacted>
Acked-by: Yinghai Lu <redacted>
quoted hunk ↗ jump to hunk
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 9042fdbd7244..add04e70ac2a 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -288,12 +288,24 @@ 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) {
+ preempt_disable();
+
+ /*
+ * 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.
+ */
+ if (node >= 0 && node != numa_node_id()) {
int cpu;
get_online_cpus();@@ -305,6 +317,8 @@ static int pci_call_probe(struct pci_driver *drv, struct pci_dev *dev,
put_online_cpus();
} else
error = local_pci_probe(&ddi);
+
+ preempt_enable();
return error;
}