mac80211: fix station destruction in AP/mesh modes
Johannes Berg [Thu, 13 Dec 2012 21:54:58 +0000 (22:54 +0100)]
Unfortunately, commit b22cfcfcae5b, intended to speed up roaming
by avoiding the synchronize_rcu() broke AP/mesh modes as it moved
some code into that work item that will still call into the driver
at a time where it's no longer expected to handle this: after the
AP or mesh has been stopped.

To fix this problem remove the per-station work struct, maintain a
station cleanup list instead and flush this list when stations are
flushed. To keep this patch smaller for stable, do this when the
stations are flushed (sta_info_flush()). This unfortunately brings
back the original roaming delay; I'll fix that again in a separate
patch.

Also, Ben reported that the original commit could sometimes (with
many interfaces) cause long delays when an interface is set down,
due to blocking on flush_workqueue(). Since we now maintain the
cleanup list, this particular change of the original patch can be
reverted.

Cc: stable@vger.kernel.org [3.7]
Reported-by: Ben Greear <greearb@candelatech.com>
Tested-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/ieee80211_i.h
net/mac80211/iface.c
net/mac80211/sta_info.c
net/mac80211/sta_info.h

index 28fc987..2fcd274 100644 (file)
@@ -773,6 +773,10 @@ struct ieee80211_sub_if_data {
                u32 mntr_flags;
        } u;
 
+       spinlock_t cleanup_stations_lock;
+       struct list_head cleanup_stations;
+       struct work_struct cleanup_stations_wk;
+
 #ifdef CONFIG_MAC80211_DEBUGFS
        struct {
                struct dentry *dir;
index 54fb7f9..0f2a9f9 100644 (file)
@@ -868,20 +868,11 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
                cancel_work_sync(&sdata->work);
                /*
                 * When we get here, the interface is marked down.
-                * Call rcu_barrier() to wait both for the RX path
+                * Call synchronize_rcu() to wait for the RX path
                 * should it be using the interface and enqueuing
-                * frames at this very time on another CPU, and
-                * for the sta free call_rcu callbacks.
+                * frames at this very time on another CPU.
                 */
-               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);
-
+               synchronize_rcu();
                skb_queue_purge(&sdata->skb_queue);
 
                /*
@@ -1501,6 +1492,15 @@ static void ieee80211_assign_perm_addr(struct ieee80211_local *local,
        mutex_unlock(&local->iflist_mtx);
 }
 
+static void ieee80211_cleanup_sdata_stas_wk(struct work_struct *wk)
+{
+       struct ieee80211_sub_if_data *sdata;
+
+       sdata = container_of(wk, struct ieee80211_sub_if_data, cleanup_stations_wk);
+
+       ieee80211_cleanup_sdata_stas(sdata);
+}
+
 int ieee80211_if_add(struct ieee80211_local *local, const char *name,
                     struct wireless_dev **new_wdev, enum nl80211_iftype type,
                     struct vif_params *params)
@@ -1576,6 +1576,10 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name,
 
        INIT_LIST_HEAD(&sdata->key_list);
 
+       spin_lock_init(&sdata->cleanup_stations_lock);
+       INIT_LIST_HEAD(&sdata->cleanup_stations);
+       INIT_WORK(&sdata->cleanup_stations_wk, ieee80211_cleanup_sdata_stas_wk);
+
        for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
                struct ieee80211_supported_band *sband;
                sband = local->hw.wiphy->bands[i];
index f3e5025..8bbd3b0 100644 (file)
@@ -91,9 +91,8 @@ static int sta_info_hash_del(struct ieee80211_local *local,
        return -ENOENT;
 }
 
-static void free_sta_work(struct work_struct *wk)
+static void cleanup_single_sta(struct sta_info *sta)
 {
-       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;
@@ -153,11 +152,35 @@ static void free_sta_work(struct work_struct *wk)
        sta_info_free(local, sta);
 }
 
+void ieee80211_cleanup_sdata_stas(struct ieee80211_sub_if_data *sdata)
+{
+       struct sta_info *sta;
+
+       spin_lock_bh(&sdata->cleanup_stations_lock);
+       while (!list_empty(&sdata->cleanup_stations)) {
+               sta = list_first_entry(&sdata->cleanup_stations,
+                                      struct sta_info, list);
+               list_del(&sta->list);
+               spin_unlock_bh(&sdata->cleanup_stations_lock);
+
+               cleanup_single_sta(sta);
+
+               spin_lock_bh(&sdata->cleanup_stations_lock);
+       }
+
+       spin_unlock_bh(&sdata->cleanup_stations_lock);
+}
+
 static void free_sta_rcu(struct rcu_head *h)
 {
        struct sta_info *sta = container_of(h, struct sta_info, rcu_head);
+       struct ieee80211_sub_if_data *sdata = sta->sdata;
 
-       ieee80211_queue_work(&sta->local->hw, &sta->free_sta_wk);
+       spin_lock(&sdata->cleanup_stations_lock);
+       list_add_tail(&sta->list, &sdata->cleanup_stations);
+       spin_unlock(&sdata->cleanup_stations_lock);
+
+       ieee80211_queue_work(&sdata->local->hw, &sdata->cleanup_stations_wk);
 }
 
 /* protected by RCU */
@@ -310,7 +333,6 @@ 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);
 
@@ -891,6 +913,20 @@ int sta_info_flush(struct ieee80211_local *local,
        }
        mutex_unlock(&local->sta_mtx);
 
+       rcu_barrier();
+
+       if (sdata) {
+               ieee80211_cleanup_sdata_stas(sdata);
+               cancel_work_sync(&sdata->cleanup_stations_wk);
+       } else {
+               mutex_lock(&local->iflist_mtx);
+               list_for_each_entry(sdata, &local->interfaces, list) {
+                       ieee80211_cleanup_sdata_stas(sdata);
+                       cancel_work_sync(&sdata->cleanup_stations_wk);
+               }
+               mutex_unlock(&local->iflist_mtx);
+       }
+
        return ret;
 }
 
index 1489bca..37c1889 100644 (file)
@@ -299,7 +299,6 @@ struct sta_info {
        spinlock_t lock;
 
        struct work_struct drv_unblock_wk;
-       struct work_struct free_sta_wk;
 
        u16 listen_interval;
 
@@ -563,4 +562,6 @@ void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta);
 void ieee80211_sta_ps_deliver_poll_response(struct sta_info *sta);
 void ieee80211_sta_ps_deliver_uapsd(struct sta_info *sta);
 
+void ieee80211_cleanup_sdata_stas(struct ieee80211_sub_if_data *sdata);
+
 #endif /* STA_INFO_H */