Merging upstream version 4.19.289.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 63c79e140..f5f201bfc 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -2445,6 +2445,24 @@ 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 pci_devices_present_work() -> survey_child_resources() ->
+	 * complete(&hbus->survey_event), even after hv_pci_query_relations()
+	 * exits and the stack variable 'comp' is no longer valid; as a result,
+	 * a hang or a page fault may happen when the complete() calls
+	 * raw_spin_lock_irqsave(). Flush hbus->wq before we exit from
+	 * hv_pci_query_relations() to avoid the issues. Note: if 'ret' is
+	 * -ENODEV, there can't be any more work item scheduled to hbus->wq
+	 * after the flush_workqueue(): see vmbus_onoffer_rescind() ->
+	 * vmbus_reset_channel_cb(), vmbus_rescind_cleanup() ->
+	 * channel->rescind = true.
+	 */
+	flush_workqueue(hbus->wq);
+
 	return ret;
 }