| Message ID | 20230404020545.32359-2-decui@microsoft.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | pci-hyper: Fix race condition bugs for fast device hotplug | expand |
From: Dexuan Cui <decui@microsoft.com> Sent: Monday, April 3, 2023 7:06 PM > > Fix the longstanding race between hv_pci_query_relations() and > survey_child_resources() by flushing the workqueue before we exit from > hv_pci_query_relations(). > > Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V > VMs") > Signed-off-by: Dexuan Cui <decui@microsoft.com> > Cc: stable@vger.kernel.org > --- > > v2: > Removed the "debug code". > No change to the patch body. > Added Cc:stable > > drivers/pci/controller/pci-hyperv.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c > index f33370b756283..b82c7cde19e66 100644 > --- a/drivers/pci/controller/pci-hyperv.c > +++ b/drivers/pci/controller/pci-hyperv.c > @@ -3308,6 +3308,19 @@ static int hv_pci_query_relations(struct hv_device *hdev) > if (!ret) > ret = wait_for_response(hdev, &comp); > > + /* > + * In the case of fast device addition/removal, it's possible that > + * vmbus_sendpacket() or wait_for_response() returns -ENODEV but we > + * already got a PCI_BUS_RELATIONS* message from the host and the > + * channel callback already scheduled a work to hbus->wq, which can be > + * running survey_child_resources() -> complete(&hbus->survey_event), > + * even after hv_pci_query_relations() exits and the stack variable > + * 'comp' is no longer valid. This can cause a strange hang issue > + * or sometimes a page fault. Flush hbus->wq before we exit from > + * hv_pci_query_relations() to avoid the issues. > + */ > + flush_workqueue(hbus->wq); > + > return ret; > } > > -- > 2.25.1 Reviewed-by: Michael Kelley <mikelley@microsoft.com>
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c index f33370b756283..b82c7cde19e66 100644 --- a/drivers/pci/controller/pci-hyperv.c +++ b/drivers/pci/controller/pci-hyperv.c @@ -3308,6 +3308,19 @@ static int hv_pci_query_relations(struct hv_device *hdev) if (!ret) ret = wait_for_response(hdev, &comp); + /* + * In the case of fast device addition/removal, it's possible that + * vmbus_sendpacket() or wait_for_response() returns -ENODEV but we + * already got a PCI_BUS_RELATIONS* message from the host and the + * channel callback already scheduled a work to hbus->wq, which can be + * running survey_child_resources() -> complete(&hbus->survey_event), + * even after hv_pci_query_relations() exits and the stack variable + * 'comp' is no longer valid. This can cause a strange hang issue + * or sometimes a page fault. Flush hbus->wq before we exit from + * hv_pci_query_relations() to avoid the issues. + */ + flush_workqueue(hbus->wq); + return ret; }
Fix the longstanding race between hv_pci_query_relations() and survey_child_resources() by flushing the workqueue before we exit from hv_pci_query_relations(). Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs") Signed-off-by: Dexuan Cui <decui@microsoft.com> Cc: stable@vger.kernel.org --- v2: Removed the "debug code". No change to the patch body. Added Cc:stable drivers/pci/controller/pci-hyperv.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)