b43legacy: Fix controller restart crash

This fixes a kernel crash on rmmod, in the case where the controller
was restarted before doing the rmmod.

Signed-off-by: Michael Buesch <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

drivers/net/wireless/b43legacy/main.c

···
 /* Locking: wl->mutex */
 static void b43legacy_wireless_core_exit(struct b43legacy_wldev *dev)
 {
-	struct b43legacy_wl *wl = dev->wl;
 	struct b43legacy_phy *phy = &dev->phy;
 	u32 macctl;
 
···
 	macctl &= ~B43legacy_MACCTL_PSM_RUN;
 	macctl |= B43legacy_MACCTL_PSM_JMP0;
 	b43legacy_write32(dev, B43legacy_MMIO_MACCTL, macctl);
-
-	mutex_unlock(&wl->mutex);
-	/* Must unlock as it would otherwise deadlock. No races here.
-	 * Cancel possibly pending workqueues. */
-	cancel_work_sync(&dev->restart_work);
-	mutex_lock(&wl->mutex);
 
 	b43legacy_leds_exit(dev);
 	b43legacy_rng_exit(dev->wl);
···
 		}
 	}
 out:
+	if (err)
+		wl->current_dev = NULL; /* Failed to init the dev. */
 	mutex_unlock(&wl->mutex);
 	if (err)
 		b43legacyerr(wl, "Controller restart FAILED\n");
···
 	struct b43legacy_wldev *wldev;
 	struct b43legacy_wl *wl;
 
+	/* Do not cancel ieee80211-workqueue based work here.
+	 * See comment in b43legacy_remove(). */
+
 	wldev = ssb_get_drvdata(dev);
 	wl = wldev->wl;
-	cancel_work_sync(&wldev->restart_work);
 	b43legacy_debugfs_remove_device(wldev);
 	b43legacy_wireless_core_detach(wldev);
 	list_del(&wldev->list);
···
 {
 	struct b43legacy_wl *wl = ssb_get_devtypedata(dev);
 	struct b43legacy_wldev *wldev = ssb_get_drvdata(dev);
+
+	/* We must cancel any work here before unregistering from ieee80211,
+	 * as the ieee80211 unreg will destroy the workqueue. */
+	cancel_work_sync(&wldev->restart_work);
 
 	B43legacy_WARN_ON(!wl);
 	if (wl->current_dev == wldev)