From: Pierre Crégut <pierre.cregut@xxxxxxxxxx> [ Upstream commit 35ff867b76576e32f34c698ccd11343f7d616204 ] 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@xxxxxxxxxx Signed-off-by: Pierre Crégut <pierre.cregut@xxxxxxxxxx> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/pci/iov.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c index deec9f9e0b616..9c116cbaa95d8 100644 --- a/drivers/pci/iov.c +++ b/drivers/pci/iov.c @@ -253,8 +253,14 @@ 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_unlock(&pdev->dev); - return sprintf(buf, "%u\n", pdev->sriov->num_VFs); + return sprintf(buf, "%u\n", num_vfs); } /* -- 2.25.1
