LinuxKPI: 802.11: keep chanctx on a reserved list

Keep the chanctx around as we may swap them.

In the future (11be) these lists likely need to be (a) limited to
maximum number of chanctx possible (see struct ieee80211_iface_limit),
and (b) with that also by radio.

For the moment keep this simple and start with a single chanctx
and build up from there when we get there.

Sponsored by:	The FreeBSD Foundation
MFC after:	3 days

sys/compat/linuxkpi/common/src/linux_80211.c

@@ -2280,13 +2280,54 @@ lkpi_init_chanctx_conf(struct ieee80211_hw *hw,
 	return (changed);
 }
 
+static struct lkpi_chanctx *
+lkpi_alloc_lchanctx(struct ieee80211_hw *hw, struct lkpi_vif *lvif)
+{
+	struct lkpi_chanctx *lchanctx;
+
+	lchanctx = malloc(sizeof(*lchanctx) + hw->chanctx_data_size,
+	    M_LKPI80211, M_WAITOK | M_ZERO);
+	lchanctx->lvif = lvif;
+
+	return (lchanctx);
+}
+
+static struct lkpi_chanctx *
+lkpi_find_lchanctx_reserved(struct ieee80211_hw *hw, struct lkpi_vif *lvif)
+{
+	struct lkpi_hw *lhw;
+	struct lkpi_chanctx *lchanctx;
+	bool found;
+
+	lhw = HW_TO_LHW(hw);
+
+	found = false;
+	rcu_read_lock();
+	list_for_each_entry_rcu(lchanctx, &lhw->lchanctx_list_reserved, entry) {
+		if (lchanctx->lvif == lvif) {
+			found = true;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	if (!found) {
+		lchanctx = lkpi_alloc_lchanctx(hw, lvif);
+		list_add_rcu(&lchanctx->entry, &lhw->lchanctx_list_reserved);
+	}
+
+	return (lchanctx);
+}
 
 static void
 lkpi_remove_chanctx(struct ieee80211_hw *hw, struct ieee80211_vif *vif)
 {
+	struct lkpi_hw *lhw;
 	struct ieee80211_chanctx_conf *chanctx_conf;
 	struct lkpi_chanctx *lchanctx;
 
+	lockdep_assert_wiphy(hw->wiphy);
+
 	chanctx_conf = rcu_dereference_protected(vif->bss_conf.chanctx_conf,
 	    lockdep_is_held(&hw->wiphy->mtx));
 
@@ -2305,7 +2346,8 @@ lkpi_remove_chanctx(struct ieee80211_hw *hw, struct ieee80211_vif *vif)
 	rcu_assign_pointer(vif->bss_conf.chanctx_conf, NULL);
 	lchanctx = CHANCTX_CONF_TO_LCHANCTX(chanctx_conf);
 	list_del(&lchanctx->entry);
-	free(lchanctx, M_LKPI80211);
+	lhw = HW_TO_LHW(hw);
+	list_add_rcu(&lchanctx->entry, &lhw->lchanctx_list_reserved);
 }
 
 /* -------------------------------------------------------------------------- */
@@ -2452,9 +2494,8 @@ lkpi_sta_scan_to_auth(struct ieee80211vap *vap, enum ieee80211_state nstate, int
 		lchanctx = CHANCTX_CONF_TO_LCHANCTX(chanctx_conf);
 		IMPROVE("diff changes for changed, working on live copy, rcu");
 	} else {
-		/* Keep separate alloc as in Linux this is rcu managed? */
-		lchanctx = malloc(sizeof(*lchanctx) + hw->chanctx_data_size,
-		    M_LKPI80211, M_WAITOK | M_ZERO);
+		lchanctx = lkpi_find_lchanctx_reserved(hw, lvif);
+		list_del(&lchanctx->entry);
 		chanctx_conf = &lchanctx->chanctx_conf;
 	}
 
@@ -2535,7 +2576,7 @@ lkpi_sta_scan_to_auth(struct ieee80211vap *vap, enum ieee80211_state nstate, int
 			rcu_assign_pointer(vif->bss_conf.chanctx_conf, NULL);
 			lchanctx = CHANCTX_CONF_TO_LCHANCTX(chanctx_conf);
 			list_del(&lchanctx->entry);
-			free(lchanctx, M_LKPI80211);
+			list_add_rcu(&lchanctx->entry, &lhw->lchanctx_list_reserved);
 			goto out;
 		}
 	}
@@ -3954,6 +3995,10 @@ lkpi_ic_vap_create(struct ieee80211com *ic, const char name[IFNAMSIZ],
 	/* Need to fill in other fields as well. */
 	IMPROVE();
 
+	/* Create a chanctx to be used later. */
+	IMPROVE("lkpi_alloc_lchanctx reserved as many as can be");
+	(void) lkpi_find_lchanctx_reserved(hw, lvif);
+
 	/* XXX-BZ hardcoded for now! */
 #if 1
 	RCU_INIT_POINTER(vif->bss_conf.chanctx_conf, NULL);
@@ -6444,6 +6489,7 @@ linuxkpi_ieee80211_alloc_hw(size_t priv_len, const struct ieee80211_ops *ops)
 
 	/* Chanctx_conf */
 	INIT_LIST_HEAD(&lhw->lchanctx_list);
+	INIT_LIST_HEAD(&lhw->lchanctx_list_reserved);
 
 	/* Deferred RX path. */
 	LKPI_80211_LHW_RXQ_LOCK_INIT(lhw);
@@ -6518,6 +6564,7 @@ linuxkpi_ieee80211_iffree(struct ieee80211_hw *hw)
 	    __func__, lhw, mbufq_len(&lhw->rxq)));
 	LKPI_80211_LHW_RXQ_LOCK_DESTROY(lhw);
 
+	wiphy_lock(hw->wiphy);
 	/* Chanctx_conf. */
 	if (!list_empty_careful(&lhw->lchanctx_list)) {
 		struct lkpi_chanctx *lchanctx, *next;
@@ -6530,9 +6577,21 @@ linuxkpi_ieee80211_iffree(struct ieee80211_hw *hw)
 				lkpi_80211_mo_remove_chanctx(hw, chanctx_conf);
 			}
 			list_del(&lchanctx->entry);
+			list_add_rcu(&lchanctx->entry, &lhw->lchanctx_list_reserved);
+		}
+	}
+	if (!list_empty_careful(&lhw->lchanctx_list_reserved)) {
+		struct lkpi_chanctx *lchanctx, *next;
+
+		list_for_each_entry_safe(lchanctx, next, &lhw->lchanctx_list_reserved, entry) {
+			list_del(&lchanctx->entry);
+			if (lchanctx->added_to_drv)
+				panic("%s: lchanctx %p on reserved list still added_to_drv\n",
+				    __func__, lchanctx);
 			free(lchanctx, M_LKPI80211);
 		}
 	}
+	wiphy_unlock(hw->wiphy);
 
 	LKPI_80211_LHW_MC_LOCK(lhw);
 	lkpi_cleanup_mcast_list_locked(lhw);

sys/compat/linuxkpi/common/src/linux_80211.h

@@ -250,6 +250,7 @@ struct lkpi_hw {	/* name it mac80211_sc? */
 	struct sx			lvif_sx;
 
 	struct list_head		lchanctx_list;
+	struct list_head		lchanctx_list_reserved;
 	struct netdev_hw_addr_list	mc_list;
 	unsigned int			mc_flags;
 	struct sx			mc_sx;
@@ -330,6 +331,7 @@ struct lkpi_chanctx {
 	struct list_head		entry;
 
 	bool				added_to_drv;	/* Managed by MO */
+	struct lkpi_vif			*lvif;		/* Backpointer. */
 
 	struct ieee80211_chanctx_conf	chanctx_conf __aligned(CACHE_LINE_SIZE);
 };