wifi: cfg80211: add a work abstraction with special semantics

Add a work abstraction at the cfg80211 level that will always
hold the wiphy_lock() for any work executed and therefore also
can be canceled safely (without waiting) while holding that.
This improves on what we do now as with the new wiphy works we
don't have to worry about locking while cancelling them safely.

Also, don't let such works run while the device is suspended,
since they'll likely need to interact with the device. Flush
them before suspend though.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 122 insertions, 0 deletions

diff --git a/net/wireless/core.c b/net/wireless/core.c
index 151a8567d2a5..ca585e96d535 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -413,6 +413,34 @@ static void cfg80211_propagate_cac_done_wk(struct work_struct *work)
 	rtnl_unlock();
 }
 
+static void cfg80211_wiphy_work(struct work_struct *work)
+{
+	struct cfg80211_registered_device *rdev;
+	struct wiphy_work *wk;
+
+	rdev = container_of(work, struct cfg80211_registered_device, wiphy_work);
+
+	wiphy_lock(&rdev->wiphy);
+	if (rdev->suspended)
+		goto out;
+
+	spin_lock_irq(&rdev->wiphy_work_lock);
+	wk = list_first_entry_or_null(&rdev->wiphy_work_list,
+				      struct wiphy_work, entry);
+	if (wk) {
+		list_del_init(&wk->entry);
+		if (!list_empty(&rdev->wiphy_work_list))
+			schedule_work(work);
+		spin_unlock_irq(&rdev->wiphy_work_lock);
+
+		wk->func(&rdev->wiphy, wk);
+	} else {
+		spin_unlock_irq(&rdev->wiphy_work_lock);
+	}
+out:
+	wiphy_unlock(&rdev->wiphy);
+}
+
 /* exported functions */
 
 struct wiphy *wiphy_new_nm(const struct cfg80211_ops *ops, int sizeof_priv,
@@ -538,6 +566,9 @@ use_default_name:
 		return NULL;
 	}
 
+	INIT_WORK(&rdev->wiphy_work, cfg80211_wiphy_work);
+	INIT_LIST_HEAD(&rdev->wiphy_work_list);
+	spin_lock_init(&rdev->wiphy_work_lock);
 	INIT_WORK(&rdev->rfkill_block, cfg80211_rfkill_block_work);
 	INIT_WORK(&rdev->conn_work, cfg80211_conn_work);
 	INIT_WORK(&rdev->event_work, cfg80211_event_work);
@@ -1035,6 +1066,31 @@ void wiphy_rfkill_start_polling(struct wiphy *wiphy)
 }
 EXPORT_SYMBOL(wiphy_rfkill_start_polling);
 
+void cfg80211_process_wiphy_works(struct cfg80211_registered_device *rdev)
+{
+	unsigned int runaway_limit = 100;
+	unsigned long flags;
+
+	lockdep_assert_held(&rdev->wiphy.mtx);
+
+	spin_lock_irqsave(&rdev->wiphy_work_lock, flags);
+	while (!list_empty(&rdev->wiphy_work_list)) {
+		struct wiphy_work *wk;
+
+		wk = list_first_entry(&rdev->wiphy_work_list,
+				      struct wiphy_work, entry);
+		list_del_init(&wk->entry);
+		spin_unlock_irqrestore(&rdev->wiphy_work_lock, flags);
+
+		wk->func(&rdev->wiphy, wk);
+
+		spin_lock_irqsave(&rdev->wiphy_work_lock, flags);
+		if (WARN_ON(--runaway_limit == 0))
+			INIT_LIST_HEAD(&rdev->wiphy_work_list);
+	}
+	spin_unlock_irqrestore(&rdev->wiphy_work_lock, flags);
+}
+
 void wiphy_unregister(struct wiphy *wiphy)
 {
 	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
@@ -1077,9 +1133,15 @@ void wiphy_unregister(struct wiphy *wiphy)
 	if (rdev->wiphy.wowlan_config && rdev->ops->set_wakeup)
 		rdev_set_wakeup(rdev, false);
 #endif
+
+	/* surely nothing is reachable now, clean up work */
+	cfg80211_process_wiphy_works(rdev);
 	wiphy_unlock(&rdev->wiphy);
 	rtnl_unlock();
 
+	/* this has nothing to do now but make sure it's gone */
+	cancel_work_sync(&rdev->wiphy_work);
+
 	flush_work(&rdev->scan_done_wk);
 	cancel_work_sync(&rdev->conn_work);
 	flush_work(&rdev->event_work);
@@ -1569,6 +1631,66 @@ static struct pernet_operations cfg80211_pernet_ops = {
 	.exit = cfg80211_pernet_exit,
 };
 
+void wiphy_work_queue(struct wiphy *wiphy, struct wiphy_work *work)
+{
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
+	unsigned long flags;
+
+	spin_lock_irqsave(&rdev->wiphy_work_lock, flags);
+	if (list_empty(&work->entry))
+		list_add_tail(&work->entry, &rdev->wiphy_work_list);
+	spin_unlock_irqrestore(&rdev->wiphy_work_lock, flags);
+
+	schedule_work(&rdev->wiphy_work);
+}
+EXPORT_SYMBOL_GPL(wiphy_work_queue);
+
+void wiphy_work_cancel(struct wiphy *wiphy, struct wiphy_work *work)
+{
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wiphy);
+	unsigned long flags;
+
+	lockdep_assert_held(&wiphy->mtx);
+
+	spin_lock_irqsave(&rdev->wiphy_work_lock, flags);
+	if (!list_empty(&work->entry))
+		list_del_init(&work->entry);
+	spin_unlock_irqrestore(&rdev->wiphy_work_lock, flags);
+}
+EXPORT_SYMBOL_GPL(wiphy_work_cancel);
+
+void wiphy_delayed_work_timer(struct timer_list *t)
+{
+	struct wiphy_delayed_work *dwork = from_timer(dwork, t, timer);
+
+	wiphy_work_queue(dwork->wiphy, &dwork->work);
+}
+EXPORT_SYMBOL(wiphy_delayed_work_timer);
+
+void wiphy_delayed_work_queue(struct wiphy *wiphy,
+			      struct wiphy_delayed_work *dwork,
+			      unsigned long delay)
+{
+	if (!delay) {
+		wiphy_work_queue(wiphy, &dwork->work);
+		return;
+	}
+
+	dwork->wiphy = wiphy;
+	mod_timer(&dwork->timer, jiffies + delay);
+}
+EXPORT_SYMBOL_GPL(wiphy_delayed_work_queue);
+
+void wiphy_delayed_work_cancel(struct wiphy *wiphy,
+			       struct wiphy_delayed_work *dwork)
+{
+	lockdep_assert_held(&wiphy->mtx);
+
+	del_timer_sync(&dwork->timer);
+	wiphy_work_cancel(wiphy, &dwork->work);
+}
+EXPORT_SYMBOL_GPL(wiphy_delayed_work_cancel);
+
 static int __init cfg80211_init(void)
 {
 	int err;