cfg80211: avoid holding the RTNL when calling the driver

Currently, _everything_ in cfg80211 holds the RTNL, and if you
have a slow USB device (or a few) you can get some bad lock
contention on that.

Fix that by re-adding a mutex to each wiphy/rdev as we had at
some point, so we have locking for the wireless_dev lists and
all the other things in there, and also so that drivers still
don't have to worry too much about it (they still won't get
parallel calls for a single device).

Then, we can restrict the RTNL to a few cases where we add or
remove interfaces and really need the added protection. Some
of the global list management still also uses the RTNL, since
we need to have it anyway for netdev management, but we only
hold the RTNL for very short periods of time here.

Link: https://lore.kernel.org/r/20210122161942.81df9f5e047a.I4a8e1a60b18863ea8c5e6d3a0faeafb2d45b2f40@changeid
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> [marvell driver issues]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

3 files changed, 20 insertions, 16 deletions

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
index 6cf308d5934c..ea78fe527c5d 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
@@ -633,7 +633,7 @@ static const struct net_device_ops brcmf_netdev_ops_pri = {
 	.ndo_set_rx_mode = brcmf_netdev_set_multicast_list
 };
 
-int brcmf_net_attach(struct brcmf_if *ifp, bool rtnl_locked)
+int brcmf_net_attach(struct brcmf_if *ifp, bool locked)
 {
 	struct brcmf_pub *drvr = ifp->drvr;
 	struct net_device *ndev;
@@ -656,7 +656,7 @@ int brcmf_net_attach(struct brcmf_if *ifp, bool rtnl_locked)
 	INIT_WORK(&ifp->multicast_work, _brcmf_set_multicast_list);
 	INIT_WORK(&ifp->ndoffload_work, _brcmf_update_ndtable);
 
-	if (rtnl_locked)
+	if (locked)
 		err = cfg80211_register_netdevice(ndev);
 	else
 		err = register_netdev(ndev);
@@ -677,10 +677,10 @@ fail:
 	return -EBADE;
 }
 
-void brcmf_net_detach(struct net_device *ndev, bool rtnl_locked)
+void brcmf_net_detach(struct net_device *ndev, bool locked)
 {
 	if (ndev->reg_state == NETREG_REGISTERED) {
-		if (rtnl_locked)
+		if (locked)
 			cfg80211_unregister_netdevice(ndev);
 		else
 			unregister_netdev(ndev);
@@ -909,7 +909,7 @@ struct brcmf_if *brcmf_add_if(struct brcmf_pub *drvr, s32 bsscfgidx, s32 ifidx,
 }
 
 static void brcmf_del_if(struct brcmf_pub *drvr, s32 bsscfgidx,
-			 bool rtnl_locked)
+			 bool locked)
 {
 	struct brcmf_if *ifp;
 	int ifidx;
@@ -938,7 +938,7 @@ static void brcmf_del_if(struct brcmf_pub *drvr, s32 bsscfgidx,
 			cancel_work_sync(&ifp->multicast_work);
 			cancel_work_sync(&ifp->ndoffload_work);
 		}
-		brcmf_net_detach(ifp->ndev, rtnl_locked);
+		brcmf_net_detach(ifp->ndev, locked);
 	} else {
 		/* Only p2p device interfaces which get dynamically created
 		 * end up here. In this case the p2p module should be informed
@@ -947,7 +947,7 @@ static void brcmf_del_if(struct brcmf_pub *drvr, s32 bsscfgidx,
 		 * serious troublesome side effects. The p2p module will clean
 		 * up the ifp if needed.
 		 */
-		brcmf_p2p_ifp_removed(ifp, rtnl_locked);
+		brcmf_p2p_ifp_removed(ifp, locked);
 		kfree(ifp);
 	}
 
@@ -956,14 +956,14 @@ static void brcmf_del_if(struct brcmf_pub *drvr, s32 bsscfgidx,
 		drvr->if2bss[ifidx] = BRCMF_BSSIDX_INVALID;
 }
 
-void brcmf_remove_interface(struct brcmf_if *ifp, bool rtnl_locked)
+void brcmf_remove_interface(struct brcmf_if *ifp, bool locked)
 {
 	if (!ifp || WARN_ON(ifp->drvr->iflist[ifp->bsscfgidx] != ifp))
 		return;
 	brcmf_dbg(TRACE, "Enter, bsscfgidx=%d, ifidx=%d\n", ifp->bsscfgidx,
 		  ifp->ifidx);
 	brcmf_proto_del_if(ifp->drvr, ifp);
-	brcmf_del_if(ifp->drvr, ifp->bsscfgidx, rtnl_locked);
+	brcmf_del_if(ifp->drvr, ifp->bsscfgidx, locked);
 }
 
 static int brcmf_psm_watchdog_notify(struct brcmf_if *ifp,
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.h b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.h
index 5767d665cee5..8212c9de14f1 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.h
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.h
@@ -201,16 +201,16 @@ int brcmf_netdev_wait_pend8021x(struct brcmf_if *ifp);
 char *brcmf_ifname(struct brcmf_if *ifp);
 struct brcmf_if *brcmf_get_ifp(struct brcmf_pub *drvr, int ifidx);
 void brcmf_configure_arp_nd_offload(struct brcmf_if *ifp, bool enable);
-int brcmf_net_attach(struct brcmf_if *ifp, bool rtnl_locked);
+int brcmf_net_attach(struct brcmf_if *ifp, bool locked);
 struct brcmf_if *brcmf_add_if(struct brcmf_pub *drvr, s32 bsscfgidx, s32 ifidx,
 			      bool is_p2pdev, const char *name, u8 *mac_addr);
-void brcmf_remove_interface(struct brcmf_if *ifp, bool rtnl_locked);
+void brcmf_remove_interface(struct brcmf_if *ifp, bool locked);
 void brcmf_txflowblock_if(struct brcmf_if *ifp,
 			  enum brcmf_netif_stop_reason reason, bool state);
 void brcmf_txfinalize(struct brcmf_if *ifp, struct sk_buff *txp, bool success);
 void brcmf_netif_rx(struct brcmf_if *ifp, struct sk_buff *skb, bool inirq);
 void brcmf_netif_mon_rx(struct brcmf_if *ifp, struct sk_buff *skb);
-void brcmf_net_detach(struct net_device *ndev, bool rtnl_locked);
+void brcmf_net_detach(struct net_device *ndev, bool locked);
 int brcmf_net_mon_attach(struct brcmf_if *ifp);
 void brcmf_net_setcarrier(struct brcmf_if *ifp, bool on);
 int __init brcmf_core_init(void);
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
index ec6fc7a150a6..6d30a0fcecea 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
@@ -2430,7 +2430,7 @@ int brcmf_p2p_del_vif(struct wiphy *wiphy, struct wireless_dev *wdev)
 	return err;
 }
 
-void brcmf_p2p_ifp_removed(struct brcmf_if *ifp, bool rtnl_locked)
+void brcmf_p2p_ifp_removed(struct brcmf_if *ifp, bool locked)
 {
 	struct brcmf_cfg80211_info *cfg;
 	struct brcmf_cfg80211_vif *vif;
@@ -2439,11 +2439,15 @@ void brcmf_p2p_ifp_removed(struct brcmf_if *ifp, bool rtnl_locked)
 	vif = ifp->vif;
 	cfg = wdev_to_cfg(&vif->wdev);
 	cfg->p2p.bss_idx[P2PAPI_BSSCFG_DEVICE].vif = NULL;
-	if (!rtnl_locked)
+	if (locked) {
 		rtnl_lock();
-	cfg80211_unregister_wdev(&vif->wdev);
-	if (!rtnl_locked)
+		wiphy_lock(cfg->wiphy);
+		cfg80211_unregister_wdev(&vif->wdev);
+		wiphy_unlock(cfg->wiphy);
 		rtnl_unlock();
+	} else {
+		cfg80211_unregister_wdev(&vif->wdev);
+	}
 	brcmf_free_vif(vif);
 }