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Commit b22cfcfc authored by Eliad Peller's avatar Eliad Peller Committed by Johannes Berg
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mac80211: use call_rcu() on sta deletion 



mac80211 calls synchronize_rcu() on sta deletion,
which increase the roaming time significantly.

Convert it into a call_rcu() mechanism, in order
to avoid blocking. Since some of the cleanup
functions might sleep, schedule from the call_rcu
callback a new work that will do the actual cleanup.

In order to make sure the cleanup occurs before
the interface went down, flush local->workqueue
on ieee80211_do_stop().

Signed-off-by: default avatarYoni Divinsky <yoni.divinsky@ti.com>
Signed-off-by: default avatarEliad Peller <eliad@wizery.com>
Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent e548c49e

net/mac80211/iface.c

+12 −3
Original line number Diff line number Diff line
@@ -793,11 +793,20 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata, 
		flush_work(&sdata->work);

		/*

		 * When we get here, the interface is marked down.

		 * Call synchronize_rcu() to wait for the RX path

		 * Call rcu_barrier() to wait both for the RX path

		 * should it be using the interface and enqueuing

		 * frames at this very time on another CPU.

		 * frames at this very time on another CPU, and

		 * for the sta free call_rcu callbacks.

		 */

		synchronize_rcu();

		rcu_barrier();



		/*

		 * free_sta_rcu() enqueues a work for the actual

		 * sta cleanup, so we need to flush it while

		 * sdata is still valid.

		 */

		flush_workqueue(local->workqueue);



		skb_queue_purge(&sdata->skb_queue);



		/*

net/mac80211/sta_info.c

+67 −54
Original line number Diff line number Diff line
@@ -91,6 +91,70 @@ static int sta_info_hash_del(struct ieee80211_local *local, 
	return -ENOENT;

}



static void free_sta_work(struct work_struct *wk)

{

	struct sta_info *sta = container_of(wk, struct sta_info, free_sta_wk);

	int ac, i;

	struct tid_ampdu_tx *tid_tx;

	struct ieee80211_sub_if_data *sdata = sta->sdata;

	struct ieee80211_local *local = sdata->local;



	/*

	 * At this point, when being called as call_rcu callback,

	 * neither mac80211 nor the driver can reference this

	 * sta struct any more except by still existing timers

	 * associated with this station that we clean up below.

	 */



	if (test_sta_flag(sta, WLAN_STA_PS_STA)) {

		BUG_ON(!sdata->bss);



		clear_sta_flag(sta, WLAN_STA_PS_STA);



		atomic_dec(&sdata->bss->num_sta_ps);

		sta_info_recalc_tim(sta);

	}



	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {

		local->total_ps_buffered -= skb_queue_len(&sta->ps_tx_buf[ac]);

		__skb_queue_purge(&sta->ps_tx_buf[ac]);

		__skb_queue_purge(&sta->tx_filtered[ac]);

	}



#ifdef CONFIG_MAC80211_MESH

	if (ieee80211_vif_is_mesh(&sdata->vif)) {

		mesh_accept_plinks_update(sdata);

		mesh_plink_deactivate(sta);

		del_timer_sync(&sta->plink_timer);

	}

#endif



	cancel_work_sync(&sta->drv_unblock_wk);



	/*

	 * Destroy aggregation state here. It would be nice to wait for the

	 * driver to finish aggregation stop and then clean up, but for now

	 * drivers have to handle aggregation stop being requested, followed

	 * directly by station destruction.

	 */

	for (i = 0; i < STA_TID_NUM; i++) {

		tid_tx = rcu_dereference_raw(sta->ampdu_mlme.tid_tx[i]);

		if (!tid_tx)

			continue;

		__skb_queue_purge(&tid_tx->pending);

		kfree(tid_tx);

	}



	sta_info_free(local, sta);

}



static void free_sta_rcu(struct rcu_head *h)

{

	struct sta_info *sta = container_of(h, struct sta_info, rcu_head);



	ieee80211_queue_work(&sta->local->hw, &sta->free_sta_wk);

}



/* protected by RCU */

struct sta_info *sta_info_get(struct ieee80211_sub_if_data *sdata,

			      const u8 *addr)
@@ -241,6 +305,7 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata, 


	spin_lock_init(&sta->lock);

	INIT_WORK(&sta->drv_unblock_wk, sta_unblock);

	INIT_WORK(&sta->free_sta_wk, free_sta_work);

	INIT_WORK(&sta->ampdu_mlme.work, ieee80211_ba_session_work);

	mutex_init(&sta->ampdu_mlme.mtx);
@@ -654,8 +719,7 @@ int __must_check __sta_info_destroy(struct sta_info *sta) 
{

	struct ieee80211_local *local;

	struct ieee80211_sub_if_data *sdata;

	int ret, i, ac;

	struct tid_ampdu_tx *tid_tx;

	int ret, i;



	might_sleep();
@@ -711,65 +775,14 @@ int __must_check __sta_info_destroy(struct sta_info *sta) 
		WARN_ON_ONCE(ret != 0);

	}



	/*

	 * At this point, after we wait for an RCU grace period,

	 * neither mac80211 nor the driver can reference this

	 * sta struct any more except by still existing timers

	 * associated with this station that we clean up below.

	 */

	synchronize_rcu();



	if (test_sta_flag(sta, WLAN_STA_PS_STA)) {

		BUG_ON(!sdata->bss);



		clear_sta_flag(sta, WLAN_STA_PS_STA);



		atomic_dec(&sdata->bss->num_sta_ps);

		sta_info_recalc_tim(sta);

	}



	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {

		local->total_ps_buffered -= skb_queue_len(&sta->ps_tx_buf[ac]);

		__skb_queue_purge(&sta->ps_tx_buf[ac]);

		__skb_queue_purge(&sta->tx_filtered[ac]);

	}



#ifdef CONFIG_MAC80211_MESH

	if (ieee80211_vif_is_mesh(&sdata->vif))

		mesh_accept_plinks_update(sdata);

#endif



	sta_dbg(sdata, "Removed STA %pM\n", sta->sta.addr);



	cancel_work_sync(&sta->drv_unblock_wk);



	cfg80211_del_sta(sdata->dev, sta->sta.addr, GFP_KERNEL);



	rate_control_remove_sta_debugfs(sta);

	ieee80211_sta_debugfs_remove(sta);



#ifdef CONFIG_MAC80211_MESH

	if (ieee80211_vif_is_mesh(&sta->sdata->vif)) {

		mesh_plink_deactivate(sta);

		del_timer_sync(&sta->plink_timer);

	}

#endif



	/*

	 * Destroy aggregation state here. It would be nice to wait for the

	 * driver to finish aggregation stop and then clean up, but for now

	 * drivers have to handle aggregation stop being requested, followed

	 * directly by station destruction.

	 */

	for (i = 0; i < STA_TID_NUM; i++) {

		tid_tx = rcu_dereference_raw(sta->ampdu_mlme.tid_tx[i]);

		if (!tid_tx)

			continue;

		__skb_queue_purge(&tid_tx->pending);

		kfree(tid_tx);

	}



	sta_info_free(local, sta);

	call_rcu(&sta->rcu_head, free_sta_rcu);



	return 0;

}

net/mac80211/sta_info.h

+2 −0
Original line number Diff line number Diff line
@@ -287,6 +287,7 @@ struct sta_ampdu_mlme { 
struct sta_info {

	/* General information, mostly static */

	struct list_head list;

	struct rcu_head rcu_head;

	struct sta_info __rcu *hnext;

	struct ieee80211_local *local;

	struct ieee80211_sub_if_data *sdata;
@@ -297,6 +298,7 @@ struct sta_info { 
	spinlock_t lock;



	struct work_struct drv_unblock_wk;

	struct work_struct free_sta_wk;



	u16 listen_interval;