On Thu, 3 Oct 2019 17:10:07 -0500, Bjorn Helgaas wrote: > On Thu, Oct 03, 2019 at 11:04:45AM +0200, CREGUT Pierre IMT/OLN wrote: > > Le 02/10/2019 à 01:45, Bjorn Helgaas a écrit : > > > On Fri, Apr 26, 2019 at 10:11:54AM +0200, CREGUT Pierre IMT/OLN wrote: > > > > I also initially thought that kobject_uevent generated the netlink event > > > > but this is not the case. This is generated by the specific driver in use. > > > > For the Intel i40e driver, this is the call to i40e_do_reset_safe in > > > > i40e_pci_sriov_configure that sends the event. > > > > It is followed by i40e_pci_sriov_enable that calls i40e_alloc_vfs that > > > > finally calls the generic pci_enable_sriov function. > > > I don't know anything about netlink. The script from the bugzilla > > > (https://bugzilla.kernel.org/show_bug.cgi?id=202991) looks like it > > > runs > > > > > > ip monitor dev enp9s0f2 > > > > > > What are the actual netlink events you see? Are they related to a > > > device being removed? > > > > We have netlink events both when num_vfs goes from 0 to N and from N to 0. > > Indeed you have to go to 0 before going to M with M != N. > > Right. FWIW I think this netlink event is an artefact of i40e implementation, and is not something the networking stack generates. Hopefully Alex can correct me if I'm wrong, but I don't think most drivers will generate such an event. > commit 0940fc95da45 > Author: Pierre Crégut <pierre.cregut@xxxxxxxxxx> > Date: Wed Sep 11 09:27:36 2019 +0200 > > PCI/IOV: Serialize sysfs sriov_numvfs reads vs writes > > When sriov_numvfs is being updated, drivers may notify about new devices > before they are reflected in sriov->num_VFs, so concurrent sysfs reads > previously returned stale values. > > Serialize the sysfs read vs the write so the read returns the correct > num_VFs value. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202991 > Link: https://lore.kernel.org/r/20190911072736.32091-1-pierre.cregut@xxxxxxxxxx > Signed-off-by: Pierre Crégut <pierre.cregut@xxxxxxxxxx> > Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c > index b3f972e8cfed..e77562aabbae 100644 > --- a/drivers/pci/iov.c > +++ b/drivers/pci/iov.c > @@ -254,8 +254,14 @@ static ssize_t sriov_numvfs_show(struct device *dev, > char *buf) > { > struct pci_dev *pdev = to_pci_dev(dev); > + u16 num_vfs; > + > + /* Serialize vs sriov_numvfs_store() so readers see valid num_VFs */ > + device_lock(&pdev->dev); > + num_vfs = pdev->sriov->num_VFs; > + device_lock(&pdev->dev); > > - return sprintf(buf, "%u\n", pdev->sriov->num_VFs); > + return sprintf(buf, "%u\n", num_vfs); > } > > /* The change makes sense to me!
