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>

include/net/cfg80211.h

@@ -5724,12 +5724,17 @@ struct cfg80211_cqm_config;
  * wiphy_lock - lock the wiphy
  * @wiphy: the wiphy to lock
  *
- * This is mostly exposed so it can be done around registering and
- * unregistering netdevs that aren't created through cfg80211 calls,
- * since that requires locking in cfg80211 when the notifiers is
- * called, but that cannot differentiate which way it's called.
+ * This is needed around registering and unregistering netdevs that
+ * aren't created through cfg80211 calls, since that requires locking
+ * in cfg80211 when the notifiers is called, but that cannot
+ * differentiate which way it's called.
+ *
+ * It can also be used by drivers for their own purposes.
  *
  * When cfg80211 ops are called, the wiphy is already locked.
+ *
+ * Note that this makes sure that no workers that have been queued
+ * with wiphy_queue_work() are running.
  */
 static inline void wiphy_lock(struct wiphy *wiphy)
 	__acquires(&wiphy->mtx)
@@ -5749,6 +5754,88 @@ static inline void wiphy_unlock(struct wiphy *wiphy)
 	mutex_unlock(&wiphy->mtx);
 }
 
+struct wiphy_work;
+typedef void (*wiphy_work_func_t)(struct wiphy *, struct wiphy_work *);
+
+struct wiphy_work {
+	struct list_head entry;
+	wiphy_work_func_t func;
+};
+
+static inline void wiphy_work_init(struct wiphy_work *work,
+				   wiphy_work_func_t func)
+{
+	INIT_LIST_HEAD(&work->entry);
+	work->func = func;
+}
+
+/**
+ * wiphy_work_queue - queue work for the wiphy
+ * @wiphy: the wiphy to queue for
+ * @work: the work item
+ *
+ * This is useful for work that must be done asynchronously, and work
+ * queued here has the special property that the wiphy mutex will be
+ * held as if wiphy_lock() was called, and that it cannot be running
+ * after wiphy_lock() was called. Therefore, wiphy_cancel_work() can
+ * use just cancel_work() instead of cancel_work_sync(), it requires
+ * being in a section protected by wiphy_lock().
+ */
+void wiphy_work_queue(struct wiphy *wiphy, struct wiphy_work *work);
+
+/**
+ * wiphy_work_cancel - cancel previously queued work
+ * @wiphy: the wiphy, for debug purposes
+ * @work: the work to cancel
+ *
+ * Cancel the work *without* waiting for it, this assumes being
+ * called under the wiphy mutex acquired by wiphy_lock().
+ */
+void wiphy_work_cancel(struct wiphy *wiphy, struct wiphy_work *work);
+
+struct wiphy_delayed_work {
+	struct wiphy_work work;
+	struct wiphy *wiphy;
+	struct timer_list timer;
+};
+
+void wiphy_delayed_work_timer(struct timer_list *t);
+
+static inline void wiphy_delayed_work_init(struct wiphy_delayed_work *dwork,
+					   wiphy_work_func_t func)
+{
+	timer_setup(&dwork->timer, wiphy_delayed_work_timer, 0);
+	wiphy_work_init(&dwork->work, func);
+}
+
+/**
+ * wiphy_delayed_work_queue - queue delayed work for the wiphy
+ * @wiphy: the wiphy to queue for
+ * @dwork: the delayable worker
+ * @delay: number of jiffies to wait before queueing
+ *
+ * This is useful for work that must be done asynchronously, and work
+ * queued here has the special property that the wiphy mutex will be
+ * held as if wiphy_lock() was called, and that it cannot be running
+ * after wiphy_lock() was called. Therefore, wiphy_cancel_work() can
+ * use just cancel_work() instead of cancel_work_sync(), it requires
+ * being in a section protected by wiphy_lock().
+ */
+void wiphy_delayed_work_queue(struct wiphy *wiphy,
+			      struct wiphy_delayed_work *dwork,
+			      unsigned long delay);
+
+/**
+ * wiphy_delayed_work_cancel - cancel previously queued delayed work
+ * @wiphy: the wiphy, for debug purposes
+ * @dwork: the delayed work to cancel
+ *
+ * Cancel the work *without* waiting for it, this assumes being
+ * called under the wiphy mutex acquired by wiphy_lock().
+ */
+void wiphy_delayed_work_cancel(struct wiphy *wiphy,
+			       struct wiphy_delayed_work *dwork);
+
 /**
  * struct wireless_dev - wireless device state
  *

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 @@ struct wiphy *wiphy_new_nm(const struct cfg80211_ops *ops, int sizeof_priv,
 		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;

net/wireless/core.h

@@ -108,6 +108,12 @@ struct cfg80211_registered_device {
 	/* lock for all wdev lists */
 	spinlock_t mgmt_registrations_lock;
 
+	struct work_struct wiphy_work;
+	struct list_head wiphy_work_list;
+	/* protects the list above */
+	spinlock_t wiphy_work_lock;
+	bool suspended;
+
 	/* must be last because of the way we do wiphy_priv(),
 	 * and it should at least be aligned to NETDEV_ALIGN */
 	struct wiphy wiphy __aligned(NETDEV_ALIGN);
@@ -453,6 +459,7 @@ int cfg80211_change_iface(struct cfg80211_registered_device *rdev,
 			  struct net_device *dev, enum nl80211_iftype ntype,
 			  struct vif_params *params);
 void cfg80211_process_rdev_events(struct cfg80211_registered_device *rdev);
+void cfg80211_process_wiphy_works(struct cfg80211_registered_device *rdev);
 void cfg80211_process_wdev_events(struct wireless_dev *wdev);
 
 bool cfg80211_does_bw_fit_range(const struct ieee80211_freq_range *freq_range,

net/wireless/sysfs.c

@@ -5,7 +5,7 @@
  *
  * Copyright 2005-2006	Jiri Benc <jbenc@suse.cz>
  * Copyright 2006	Johannes Berg <johannes@sipsolutions.net>
- * Copyright (C) 2020-2021 Intel Corporation
+ * Copyright (C) 2020-2021, 2023 Intel Corporation
  */
 
 #include <linux/device.h>
@@ -105,14 +105,18 @@ static int wiphy_suspend(struct device *dev)
 			cfg80211_leave_all(rdev);
 			cfg80211_process_rdev_events(rdev);
 		}
+		cfg80211_process_wiphy_works(rdev);
 		if (rdev->ops->suspend)
 			ret = rdev_suspend(rdev, rdev->wiphy.wowlan_config);
 		if (ret == 1) {
 			/* Driver refuse to configure wowlan */
 			cfg80211_leave_all(rdev);
 			cfg80211_process_rdev_events(rdev);
+			cfg80211_process_wiphy_works(rdev);
 			ret = rdev_suspend(rdev, NULL);
 		}
+		if (ret == 0)
+			rdev->suspended = true;
 	}
 	wiphy_unlock(&rdev->wiphy);
 	rtnl_unlock();
@@ -132,6 +136,8 @@ static int wiphy_resume(struct device *dev)
 	wiphy_lock(&rdev->wiphy);
 	if (rdev->wiphy.registered && rdev->ops->resume)
 		ret = rdev_resume(rdev);
+	rdev->suspended = false;
+	schedule_work(&rdev->wiphy_work);
 	wiphy_unlock(&rdev->wiphy);
 
 	if (ret)