eeepc-laptop: use a mutex to serialize pci hotplug (resume vs. notify)

Commit d0265f0 "eeepc-laptop: fix hot-unplug on resume" used a workqueue
to protect pci hotplug against multiple simultaneous calls during
resume.  It seems to work, but a mutex would be more appropriate.

This is in preparation to fix the potential pci hotplug race on unload.

Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/platform/x86/eeepc-laptop.c

@@ -143,7 +143,7 @@ struct eeepc_hotk {
 	struct rfkill *bluetooth_rfkill;
 	struct rfkill *wwan3g_rfkill;
 	struct hotplug_slot *hotplug_slot;
-	struct work_struct hotplug_work;
+	struct mutex hotplug_lock;
 };
 
 /* The actual device the driver binds to */
@@ -661,29 +661,31 @@ static int eeepc_get_adapter_status(struct hotplug_slot *hotplug_slot,
 	return 0;
 }
 
-static void eeepc_hotplug_work(struct work_struct *work)
+static void eeepc_rfkill_hotplug(void)
 {
 	struct pci_dev *dev;
 	struct pci_bus *bus;
 	bool blocked = eeepc_wlan_rfkill_blocked();
 
 	rfkill_set_sw_state(ehotk->wlan_rfkill, blocked);
 
+	mutex_lock(&ehotk->hotplug_lock);
+
 	if (ehotk->hotplug_slot == NULL)
-		return;
+		goto out_unlock;
 
 	bus = pci_find_bus(0, 1);
 	if (!bus) {
 		pr_warning("Unable to find PCI bus 1?\n");
-		return;
+		goto out_unlock;
 	}
 
 	if (!blocked) {
 		dev = pci_get_slot(bus, 0);
 		if (dev) {
 			/* Device already present */
 			pci_dev_put(dev);
-			return;
+			goto out_unlock;
 		}
 		dev = pci_scan_single_device(bus, 0);
 		if (dev) {
@@ -698,14 +700,17 @@ static void eeepc_hotplug_work(struct work_struct *work)
 			pci_dev_put(dev);
 		}
 	}
+
+out_unlock:
+	mutex_unlock(&ehotk->hotplug_lock);
 }
 
 static void eeepc_rfkill_notify(acpi_handle handle, u32 event, void *data)
 {
 	if (event != ACPI_NOTIFY_BUS_CHECK)
 		return;
 
-	schedule_work(&ehotk->hotplug_work);
+	eeepc_rfkill_hotplug();
 }
 
 static void eeepc_hotk_notify(struct acpi_device *device, u32 event)
@@ -896,7 +901,7 @@ static int eeepc_hotk_resume(struct acpi_device *device)
 
 		rfkill_set_sw_state(ehotk->wlan_rfkill, wlan != 1);
 
-		schedule_work(&ehotk->hotplug_work);
+		eeepc_rfkill_hotplug();
 	}
 
 	if (ehotk->bluetooth_rfkill)
@@ -1097,7 +1102,7 @@ static int eeepc_rfkill_init(struct device *dev)
 {
 	int result = 0;
 
-	INIT_WORK(&ehotk->hotplug_work, eeepc_hotplug_work);
+	mutex_init(&ehotk->hotplug_lock);
 
 	eeepc_register_rfkill_notifier("\\_SB.PCI0.P0P6");
 	eeepc_register_rfkill_notifier("\\_SB.PCI0.P0P7");