wifi: wilc1000: use SRCU instead of RCU for vif list traversal

Enabling CONFIG_PROVE_RCU_LIST raises many warnings in wilc driver, even on
some places already protected by a read critical section. An example of
such case is in wilc_get_available_idx:

=============================
WARNING: suspicious RCU usage
6.8.0-rc1+ #32 Not tainted
-----------------------------
drivers/net/wireless/microchip/wilc1000/netdev.c:944 RCU-list traversed in non-reader section!!
[...]
stack backtrace:
CPU: 0 PID: 26 Comm: kworker/0:3 Not tainted 6.8.0-rc1+ #32
Hardware name: Atmel SAMA5
Workqueue: events_freezable mmc_rescan
 unwind_backtrace from show_stack+0x18/0x1c
 show_stack from dump_stack_lvl+0x34/0x58
 dump_stack_lvl from wilc_netdev_ifc_init+0x788/0x8ec
 wilc_netdev_ifc_init from wilc_cfg80211_init+0x690/0x910
 wilc_cfg80211_init from wilc_sdio_probe+0x168/0x490
 wilc_sdio_probe from sdio_bus_probe+0x230/0x3f4
 sdio_bus_probe from really_probe+0x270/0xdf4
 really_probe from __driver_probe_device+0x1dc/0x580
 __driver_probe_device from driver_probe_device+0x60/0x140
 driver_probe_device from __device_attach_driver+0x268/0x364
 __device_attach_driver from bus_for_each_drv+0x15c/0x1cc
 bus_for_each_drv from __device_attach+0x1ec/0x3e8
 __device_attach from bus_probe_device+0x190/0x1c0
 bus_probe_device from device_add+0x10dc/0x18e4
 device_add from sdio_add_func+0x1c0/0x2c0
 sdio_add_func from mmc_attach_sdio+0xa08/0xe1c
 mmc_attach_sdio from mmc_rescan+0xa00/0xfe0
 mmc_rescan from process_one_work+0x8d4/0x169c
 process_one_work from worker_thread+0x8cc/0x1340
 worker_thread from kthread+0x448/0x510
 kthread from ret_from_fork+0x14/0x28

This warning is due to the section being protected by a srcu critical read
section, but the list traversal being done with classic RCU API. Fix the
warning by using corresponding SRCU read lock/unlock APIs. While doing so,
since we always manipulate the same list (managed through a pointer
embedded in struct_wilc), add a macro to reduce the corresponding
boilerplate in each call site.
Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/20240215-wilc_fix_rcu_usage-v1-2-f610e46c6f82@bootlin.com

drivers/net/wireless/microchip/wilc1000/cfg80211.c

@@ -1518,7 +1518,7 @@ static struct wilc_vif *wilc_get_vif_from_type(struct wilc *wl, int type)
 {
 	struct wilc_vif *vif;
 
-	list_for_each_entry_rcu(vif, &wl->vif_list, list) {
+	wilc_for_each_vif(wl, vif) {
 		if (vif->iftype == type)
 			return vif;
 	}

drivers/net/wireless/microchip/wilc1000/hif.c

@@ -107,7 +107,7 @@ static struct wilc_vif *wilc_get_vif_from_idx(struct wilc *wilc, int idx)
 	if (index < 0 || index >= WILC_NUM_CONCURRENT_IFC)
 		return NULL;
 
-	list_for_each_entry_rcu(vif, &wilc->vif_list, list) {
+	wilc_for_each_vif(wilc, vif) {
 		if (vif->idx == index)
 			return vif;
 	}

drivers/net/wireless/microchip/wilc1000/netdev.c

@@ -96,7 +96,7 @@ static struct net_device *get_if_handler(struct wilc *wilc, u8 *mac_header)
 	struct wilc_vif *vif;
 	struct ieee80211_hdr *h = (struct ieee80211_hdr *)mac_header;
 
-	list_for_each_entry_rcu(vif, &wilc->vif_list, list) {
+	wilc_for_each_vif(wilc, vif) {
 		if (vif->iftype == WILC_STATION_MODE)
 			if (ether_addr_equal_unaligned(h->addr2, vif->bssid)) {
 				ndev = vif->ndev;
@@ -132,7 +132,7 @@ int wilc_wlan_get_num_conn_ifcs(struct wilc *wilc)
 	struct wilc_vif *vif;
 
 	srcu_idx = srcu_read_lock(&wilc->srcu);
-	list_for_each_entry_rcu(vif, &wilc->vif_list, list) {
+	wilc_for_each_vif(wilc, vif) {
 		if (!is_zero_ether_addr(vif->bssid))
 			ret_val++;
 	}
@@ -146,7 +146,7 @@ static void wilc_wake_tx_queues(struct wilc *wl)
 	struct wilc_vif *ifc;
 
 	srcu_idx = srcu_read_lock(&wl->srcu);
-	list_for_each_entry_rcu(ifc, &wl->vif_list, list) {
+	wilc_for_each_vif(wl, ifc) {
 		if (ifc->mac_opened && netif_queue_stopped(ifc->ndev))
 			netif_wake_queue(ifc->ndev);
 	}
@@ -668,7 +668,7 @@ static int wilc_set_mac_addr(struct net_device *dev, void *p)
 	/* Verify MAC Address is not already in use: */
 
 	srcu_idx = srcu_read_lock(&wilc->srcu);
-	list_for_each_entry_rcu(tmp_vif, &wilc->vif_list, list) {
+	wilc_for_each_vif(wilc, tmp_vif) {
 		wilc_get_mac_address(tmp_vif, mac_addr);
 		if (ether_addr_equal(addr->sa_data, mac_addr)) {
 			if (vif != tmp_vif) {
@@ -771,7 +771,7 @@ netdev_tx_t wilc_mac_xmit(struct sk_buff *skb, struct net_device *ndev)
 		struct wilc_vif *vif;
 
 		srcu_idx = srcu_read_lock(&wilc->srcu);
-		list_for_each_entry_rcu(vif, &wilc->vif_list, list) {
+		wilc_for_each_vif(wilc, vif) {
 			if (vif->mac_opened)
 				netif_stop_queue(vif->ndev);
 		}
@@ -858,7 +858,7 @@ void wilc_wfi_mgmt_rx(struct wilc *wilc, u8 *buff, u32 size, bool is_auth)
 	struct wilc_vif *vif;
 
 	srcu_idx = srcu_read_lock(&wilc->srcu);
-	list_for_each_entry_rcu(vif, &wilc->vif_list, list) {
+	wilc_for_each_vif(wilc, vif) {
 		struct ieee80211_mgmt *mgmt = (struct ieee80211_mgmt *)buff;
 		u16 type = le16_to_cpup((__le16 *)buff);
 		u32 type_bit = BIT(type >> 4);
@@ -930,7 +930,7 @@ static u8 wilc_get_available_idx(struct wilc *wl)
 	int srcu_idx;
 
 	srcu_idx = srcu_read_lock(&wl->srcu);
-	list_for_each_entry_rcu(vif, &wl->vif_list, list) {
+	wilc_for_each_vif(wl, vif) {
 		if (vif->idx == 0)
 			idx = 1;
 		else

drivers/net/wireless/microchip/wilc1000/netdev.h

@@ -13,6 +13,7 @@
 #include <net/ieee80211_radiotap.h>
 #include <linux/if_arp.h>
 #include <linux/gpio/consumer.h>
+#include <linux/rculist.h>
 
 #include "hif.h"
 #include "wlan.h"
@@ -29,6 +30,11 @@
 
 #define TX_BACKOFF_WEIGHT_MS			1
 
+#define wilc_for_each_vif(w, v) \
+	struct wilc *_w = w; \
+	list_for_each_entry_srcu(v, &_w->vif_list, list, \
+				 srcu_read_lock_held(&_w->srcu))
+
 struct wilc_wfi_stats {
 	unsigned long rx_packets;
 	unsigned long tx_packets;

drivers/net/wireless/microchip/wilc1000/wlan.c

@@ -725,7 +725,7 @@ int wilc_wlan_handle_txq(struct wilc *wilc, u32 *txq_count)
 	mutex_lock(&wilc->txq_add_to_head_cs);
 
 	srcu_idx = srcu_read_lock(&wilc->srcu);
-	list_for_each_entry_rcu(vif, &wilc->vif_list, list)
+	wilc_for_each_vif(wilc, vif)
 		wilc_wlan_txq_filter_dup_tcp_ack(vif->ndev);
 	srcu_read_unlock(&wilc->srcu, srcu_idx);