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PCI/IOV: Serialize sysfs sriov_numvfs reads vs writes

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When sriov_numvfs is being updated, we call the driver->sriov_configure()
function, which may enable VFs and call probe functions, which may make new
devices visible.  This all happens before before sriov_numvfs_store()
updates sriov->num_VFs, so previously, concurrent sysfs reads of
sriov_numvfs returned stale values.

Serialize the sysfs read vs the write so the read returns the correct
num_VFs value.

[bhelgaas: hold device_lock instead of checking mutex_is_locked()]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=202991
Link: https://lore.kernel.org/r/20190911072736.32091-1-pierre.cregut@orange.com
Signed-off-by: Pierre Crégut <pierre.cregut@orange.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Pierre Crégut 2019-09-11 09:27:36 +02:00 committed by Bjorn Helgaas
parent 56b4cd4b7d
commit 35ff867b76
1 changed files with 7 additions and 1 deletions
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8
drivers/pci/iov.c
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@ -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;
return sprintf(buf, "%u\n", pdev->sriov->num_VFs);
/* Serialize vs sriov_numvfs_store() so readers see valid num_VFs */
device_lock(&pdev->dev);
num_vfs = pdev->sriov->num_VFs;
device_unlock(&pdev->dev);
return sprintf(buf, "%u\n", num_vfs);
}
/*