PCI: hv: Fix sleep while in non-sleep context when removing child devices from the bus

In hv_pci_bus_exit, the code is holding a spinlock while calling
pci_destroy_slot(), which takes a mutex.

This is not safe for spinlock. Fix this by moving the children to be
deleted to a list on the stack, and removing them after spinlock is
released.

Fixes: 94d2276 ("PCI: hv: Fix a race condition when removing the device")

Cc: "K. Y. Srinivasan" <[email protected]>
Cc: Haiyang Zhang <[email protected]>
Cc: Stephen Hemminger <[email protected]>
Cc: Wei Liu <[email protected]>
Cc: Dexuan Cui <[email protected]>
Cc: Lorenzo Pieralisi <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: "Krzysztof Wilczyński" <[email protected]>
Cc: Bjorn Helgaas <[email protected]>
Cc: Michael Kelley <[email protected]>
Reported-by: Dan Carpenter <[email protected]>
Link: https://lore.kernel.org/linux-hyperv/20210823152130.GA21501@kili/
Signed-off-by: Long Li <[email protected]>
Reviewed-by: Wei Liu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Wei Liu <[email protected]>

Author: longlimsft

drivers/pci/controller/pci-hyperv.c

@@ -3229,17 +3229,24 @@ static int hv_pci_bus_exit(struct hv_device *hdev, bool keep_devs)
 		return 0;
 
 	if (!keep_devs) {
-		/* Delete any children which might still exist. */
+		struct list_head removed;
+
+		/* Move all present children to the list on stack */
+		INIT_LIST_HEAD(&removed);
 		spin_lock_irqsave(&hbus->device_list_lock, flags);
-		list_for_each_entry_safe(hpdev, tmp, &hbus->children, list_entry) {
+		list_for_each_entry_safe(hpdev, tmp, &hbus->children, list_entry)
+			list_move_tail(&hpdev->list_entry, &removed);
+		spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+
+		/* Remove all children in the list */
+		list_for_each_entry_safe(hpdev, tmp, &removed, list_entry) {
 			list_del(&hpdev->list_entry);
 			if (hpdev->pci_slot)
 				pci_destroy_slot(hpdev->pci_slot);
 			/* For the two refs got in new_pcichild_device() */
 			put_pcichild(hpdev);
 			put_pcichild(hpdev);
 		}
-		spin_unlock_irqrestore(&hbus->device_list_lock, flags);
 	}
 
 	ret = hv_send_resources_released(hdev);