mac80211: update mesh beacon on workqueue

Instead of updating the mesh beacon immediately when
requested (which would require the sdata_lock()), defer it
to the mac80211 workqueue.

Fixes yet another deadlock on calling sta_info_flush()
with the sdata_lock() held from ieee80211_stop_mesh(). We
could just drop the sdata_lock() around the
mesh_sta_cleanup() call, but this path is also taken from
several non-locked error paths.

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
[fix comment position]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

3 files changed, 44 insertions, 12 deletions

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index a4dfb0be53d7..194be3de16dd 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -544,6 +544,7 @@ struct ieee80211_if_mesh {
         struct timer_list mesh_path_root_timer;
 
         unsigned long wrkq_flags;
+        unsigned long mbss_changed;
 
         u8 mesh_id[IEEE80211_MAX_MESH_ID_LEN];
         size_t mesh_id_len;
diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index 6c33af482df4..d5dea94216e4 100644
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -161,11 +161,8 @@ void mesh_sta_cleanup(struct sta_info *sta)
                 del_timer_sync(&sta->plink_timer);
         }
 
-        if (changed) {
-                sdata_lock(sdata);
+        if (changed)
                 ieee80211_mbss_info_change_notify(sdata, changed);
-                sdata_unlock(sdata);
-        }
 }
 
 int mesh_rmc_init(struct ieee80211_sub_if_data *sdata)
@@ -719,14 +716,18 @@ ieee80211_mesh_rebuild_beacon(struct ieee80211_sub_if_data *sdata)
 void ieee80211_mbss_info_change_notify(struct ieee80211_sub_if_data *sdata,
                                        u32 changed)
 {
-        if (sdata->vif.bss_conf.enable_beacon &&
-            (changed & (BSS_CHANGED_BEACON |
-                        BSS_CHANGED_HT |
-                        BSS_CHANGED_BASIC_RATES |
-                        BSS_CHANGED_BEACON_INT)))
-                if (ieee80211_mesh_rebuild_beacon(sdata))
-                        return;
-        ieee80211_bss_info_change_notify(sdata, changed);
+        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
+        unsigned long bits = changed;
+        u32 bit;
+
+        if (!bits)
+                return;
+
+        /* if we race with running work, worst case this work becomes a noop */
+        for_each_set_bit(bit, &bits, sizeof(changed) * BITS_PER_BYTE)
+                set_bit(bit, &ifmsh->mbss_changed);
+        set_bit(MESH_WORK_MBSS_CHANGED, &ifmsh->wrkq_flags);
+        ieee80211_queue_work(&sdata->local->hw, &sdata->work);
 }
 
 int ieee80211_start_mesh(struct ieee80211_sub_if_data *sdata)
@@ -799,6 +800,10 @@ void ieee80211_stop_mesh(struct ieee80211_sub_if_data *sdata)
         del_timer_sync(&sdata->u.mesh.mesh_path_root_timer);
         del_timer_sync(&sdata->u.mesh.mesh_path_timer);
 
+        /* clear any mesh work (for next join) we may have accrued */
+        ifmsh->wrkq_flags = 0;
+        ifmsh->mbss_changed = 0;
+
         local->fif_other_bss--;
         atomic_dec(&local->iff_allmultis);
         ieee80211_configure_filter(local);
@@ -965,6 +970,28 @@ out:
         sdata_unlock(sdata);
 }
 
+static void mesh_bss_info_changed(struct ieee80211_sub_if_data *sdata)
+{
+        struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
+        u32 bit, changed = 0;
+
+        for_each_set_bit(bit, &ifmsh->mbss_changed,
+                         sizeof(changed) * BITS_PER_BYTE) {
+                clear_bit(bit, &ifmsh->mbss_changed);
+                changed |= BIT(bit);
+        }
+
+        if (sdata->vif.bss_conf.enable_beacon &&
+            (changed & (BSS_CHANGED_BEACON |
+                        BSS_CHANGED_HT |
+                        BSS_CHANGED_BASIC_RATES |
+                        BSS_CHANGED_BEACON_INT)))
+                if (ieee80211_mesh_rebuild_beacon(sdata))
+                        return;
+
+        ieee80211_bss_info_change_notify(sdata, changed);
+}
+
 void ieee80211_mesh_work(struct ieee80211_sub_if_data *sdata)
 {
         struct ieee80211_if_mesh *ifmsh = &sdata->u.mesh;
@@ -995,6 +1022,8 @@ void ieee80211_mesh_work(struct ieee80211_sub_if_data *sdata)
         if (test_and_clear_bit(MESH_WORK_DRIFT_ADJUST, &ifmsh->wrkq_flags))
                 mesh_sync_adjust_tbtt(sdata);
 
+        if (test_and_clear_bit(MESH_WORK_MBSS_CHANGED, &ifmsh->wrkq_flags))
+                mesh_bss_info_changed(sdata);
 out:
         sdata_unlock(sdata);
 }
diff --git a/net/mac80211/mesh.h b/net/mac80211/mesh.h
index 01a28bca6e9b..2bc7fd2f787d 100644
--- a/net/mac80211/mesh.h
+++ b/net/mac80211/mesh.h
@@ -58,6 +58,7 @@ enum mesh_path_flags {
  * @MESH_WORK_ROOT: the mesh root station needs to send a frame
  * @MESH_WORK_DRIFT_ADJUST: time to compensate for clock drift relative to other
  * mesh nodes
+ * @MESH_WORK_MBSS_CHANGED: rebuild beacon and notify driver of BSS changes
  */
 enum mesh_deferred_task_flags {
         MESH_WORK_HOUSEKEEPING,
@@ -65,6 +66,7 @@ enum mesh_deferred_task_flags {
         MESH_WORK_GROW_MPP_TABLE,
         MESH_WORK_ROOT,
         MESH_WORK_DRIFT_ADJUST,
+        MESH_WORK_MBSS_CHANGED,
 };
 
 /**