[PATCH] PCI: hv: Fix a race condition when removing the device
From: <hidden>
Date: 2021-04-19 19:26:42
Also in:
linux-pci, lkml
Subsystem:
hyper-v/azure core and drivers, pci native host bridge and endpoint drivers, pci subsystem, the rest · Maintainers:
"K. Y. Srinivasan", Haiyang Zhang, Wei Liu, Dexuan Cui, Long Li, Lorenzo Pieralisi, Krzysztof Wilczyński, Manivannan Sadhasivam, Bjorn Helgaas, Linus Torvalds
From: Long Li <longli@microsoft.com> On removing the device, any work item (hv_pci_devices_present() or hv_pci_eject_device()) scheduled on workqueue hbus->wq may still be running and race with hv_pci_remove(). This can happen because the host may send PCI_EJECT or PCI_BUS_RELATIONS(2) and decide to rescind the channel immediately after that. Fix this by flushing/stopping the workqueue of hbus before doing hbus remove. Signed-off-by: Long Li <longli@microsoft.com> --- drivers/pci/controller/pci-hyperv.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 27a17a1e4a7c..116815404313 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c@@ -3305,6 +3305,17 @@ static int hv_pci_remove(struct hv_device *hdev) hbus = hv_get_drvdata(hdev); if (hbus->state == hv_pcibus_installed) { + tasklet_disable(&hdev->channel->callback_event); + hbus->state = hv_pcibus_removing; + tasklet_enable(&hdev->channel->callback_event); + + flush_workqueue(hbus->wq); + /* + * At this point, no work is running or can be scheduled + * on hbus-wq. We can't race with hv_pci_devices_present() + * or hv_pci_eject_device(), it's safe to proceed. + */ + /* Remove the bus from PCI's point of view. */ pci_lock_rescan_remove(); pci_stop_root_bus(hbus->pci_bus);
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2.27.0