net-sysfs: convert dev->operstate reads to lockless ones

operstate_show() can omit dev_base_lock acquisition only
to read dev->operstate.

Annotate accesses to dev->operstate.

Writers still acquire dev_base_lock for mutual exclusion.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 5ad4abf..2cf4fc7 100644 (file)
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -455,7 +455,8 @@ static int br_fill_ifinfo(struct sk_buff *skb,
                          u32 filter_mask, const struct net_device *dev,
                          bool getlink)
 {
-       u8 operstate = netif_running(dev) ? dev->operstate : IF_OPER_DOWN;
+       u8 operstate = netif_running(dev) ? READ_ONCE(dev->operstate) :
+                                           IF_OPER_DOWN;
        struct nlattr *af = NULL;
        struct net_bridge *br;
        struct ifinfomsg *hdr;

diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index 429571c..1b93e05 100644 (file)
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -67,7 +67,7 @@ static void rfc2863_policy(struct net_device *dev)
 {
        unsigned char operstate = default_operstate(dev);
 
-       if (operstate == dev->operstate)
+       if (operstate == READ_ONCE(dev->operstate))
                return;
 
        write_lock(&dev_base_lock);
@@ -87,7 +87,7 @@ static void rfc2863_policy(struct net_device *dev)
                break;
        }
 
-       dev->operstate = operstate;
+       WRITE_ONCE(dev->operstate, operstate);
 
        write_unlock(&dev_base_lock);
 }

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 23ef2df..c5d164b 100644 (file)
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -325,11 +325,9 @@ static ssize_t operstate_show(struct device *dev,
        const struct net_device *netdev = to_net_dev(dev);
        unsigned char operstate;
 
-       read_lock(&dev_base_lock);
-       operstate = netdev->operstate;
+       operstate = READ_ONCE(netdev->operstate);
        if (!netif_running(netdev))
                operstate = IF_OPER_DOWN;
-       read_unlock(&dev_base_lock);
 
        if (operstate >= ARRAY_SIZE(operstates))
                return -EINVAL; /* should not happen */

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index fd47a44..43d92de 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -866,9 +866,9 @@ static void set_operstate(struct net_device *dev, unsigned char transition)
                break;
        }
 
-       if (dev->operstate != operstate) {
+       if (READ_ONCE(dev->operstate) != operstate) {
                write_lock(&dev_base_lock);
-               dev->operstate = operstate;
+               WRITE_ONCE(dev->operstate, operstate);
                write_unlock(&dev_base_lock);
                netdev_state_change(dev);
        }

diff --git a/net/hsr/hsr_device.c b/net/hsr/hsr_device.c
index 9d71b66..be0e43f 100644 (file)
--- a/net/hsr/hsr_device.c
+++ b/net/hsr/hsr_device.c
@@ -31,8 +31,8 @@ static bool is_slave_up(struct net_device *dev)
 static void __hsr_set_operstate(struct net_device *dev, int transition)
 {
        write_lock(&dev_base_lock);
-       if (dev->operstate != transition) {
-               dev->operstate = transition;
+       if (READ_ONCE(dev->operstate) != transition) {
+               WRITE_ONCE(dev->operstate, transition);
                write_unlock(&dev_base_lock);
                netdev_state_change(dev);
        } else {
@@ -78,14 +78,14 @@ static void hsr_check_announce(struct net_device *hsr_dev,
 
        hsr = netdev_priv(hsr_dev);
 
-       if (hsr_dev->operstate == IF_OPER_UP && old_operstate != IF_OPER_UP) {
+       if (READ_ONCE(hsr_dev->operstate) == IF_OPER_UP && old_operstate != IF_OPER_UP) {
                /* Went up */
                hsr->announce_count = 0;
                mod_timer(&hsr->announce_timer,
                          jiffies + msecs_to_jiffies(HSR_ANNOUNCE_INTERVAL));
        }
 
-       if (hsr_dev->operstate != IF_OPER_UP && old_operstate == IF_OPER_UP)
+       if (READ_ONCE(hsr_dev->operstate) != IF_OPER_UP && old_operstate == IF_OPER_UP)
                /* Went down */
                del_timer(&hsr->announce_timer);
 }
@@ -100,7 +100,7 @@ void hsr_check_carrier_and_operstate(struct hsr_priv *hsr)
        /* netif_stacked_transfer_operstate() cannot be used here since
         * it doesn't set IF_OPER_LOWERLAYERDOWN (?)
         */
-       old_operstate = master->dev->operstate;
+       old_operstate = READ_ONCE(master->dev->operstate);
        has_carrier = hsr_check_carrier(master);
        hsr_set_operstate(master, has_carrier);
        hsr_check_announce(master->dev, old_operstate);

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index ca1b719..2c1ed64 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -6025,7 +6025,7 @@ static int inet6_fill_ifinfo(struct sk_buff *skb, struct inet6_dev *idev,
            (dev->ifindex != dev_get_iflink(dev) &&
             nla_put_u32(skb, IFLA_LINK, dev_get_iflink(dev))) ||
            nla_put_u8(skb, IFLA_OPERSTATE,
-                      netif_running(dev) ? dev->operstate : IF_OPER_DOWN))
+                      netif_running(dev) ? READ_ONCE(dev->operstate) : IF_OPER_DOWN))
                goto nla_put_failure;
        protoinfo = nla_nest_start_noflag(skb, IFLA_PROTINFO);
        if (!protoinfo)