[PATCH v3 net-next 00/13] net: complete dev_base_lock removal

[PATCH v3 net-next 00/13] net: complete dev_base_lock removal

[Eric Dumazet]

Back in 2009 we started an effort to get rid of dev_base_lock
in favor of RCU.

It is time to finish this work.

Say goodbye to dev_base_lock !

v3: I misread kbot reports, the issue was with dev->operstate (patch 10/13)
    So dev->reg_state is back to u8, and dev->operstate becomes an u32.
    Sorry for the noise.

v2: dev->reg_state must be a standard enum, some arches
    do not support cmpxchg() on u8.

Eric Dumazet (13):
  net: annotate data-races around dev->name_assign_type
  ip_tunnel: annotate data-races around t->parms.link
  dev: annotate accesses to dev->link
  net: convert dev->reg_state to u8
  net-sysfs: convert netdev_show() to RCU
  net-sysfs: use dev_addr_sem to remove races in address_show()
  net-sysfs: convert dev->operstate reads to lockless ones
  net-sysfs: convert netstat_show() to RCU
  net: remove stale mentions of dev_base_lock in comments
  net: add netdev_set_operstate() helper
  net: remove dev_base_lock from do_setlink()
  net: remove dev_base_lock from register_netdevice() and friends.
  net: remove dev_base_lock

 Documentation/networking/netdevices.rst     |  4 +-
 drivers/net/ethernet/cisco/enic/enic_main.c |  2 +-
 drivers/net/ethernet/nvidia/forcedeth.c     |  4 +-
 drivers/net/ethernet/sfc/efx_common.c       |  2 +-
 drivers/net/ethernet/sfc/falcon/efx.c       |  2 +-
 drivers/net/ethernet/sfc/siena/efx_common.c |  2 +-
 include/linux/netdevice.h                   | 28 ++++----
 include/linux/rtnetlink.h                   |  2 +
 net/bridge/br_netlink.c                     |  3 +-
 net/core/dev.c                              | 71 +++++----------------
 net/core/link_watch.c                       | 13 ++--
 net/core/net-sysfs.c                        | 39 ++++++-----
 net/core/rtnetlink.c                        | 26 +++++---
 net/hsr/hsr_device.c                        | 28 +++-----
 net/ipv4/ip_tunnel.c                        | 27 ++++----
 net/ipv6/addrconf.c                         |  2 +-
 16 files changed, 110 insertions(+), 145 deletions(-)

-- 
2.43.0.687.g38aa6559b0-goog

[PATCH v3 net-next 01/13] net: annotate data-races around dev->name_assign_type

[Eric Dumazet]

name_assign_type_show() runs locklessly, we should annotate
accesses to dev->name_assign_type.

Alternative would be to grab devnet_rename_sem semaphore
from name_assign_type_show(), but this would not bring
more accuracy.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/core/dev.c       | 6 +++---
 net/core/net-sysfs.c | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 31f2c97d19903a7b4ce92292dd53486c0043cd1b..7bba4a47231726d666348539538ae94eb248fc3a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1220,13 +1220,13 @@ int dev_change_name(struct net_device *dev, const char *newname)
 			    dev->flags & IFF_UP ? " (while UP)" : "");
 
 	old_assign_type = dev->name_assign_type;
-	dev->name_assign_type = NET_NAME_RENAMED;
+	WRITE_ONCE(dev->name_assign_type, NET_NAME_RENAMED);
 
 rollback:
 	ret = device_rename(&dev->dev, dev->name);
 	if (ret) {
 		memcpy(dev->name, oldname, IFNAMSIZ);
-		dev->name_assign_type = old_assign_type;
+		WRITE_ONCE(dev->name_assign_type, old_assign_type);
 		up_write(&devnet_rename_sem);
 		return ret;
 	}
@@ -1255,7 +1255,7 @@ int dev_change_name(struct net_device *dev, const char *newname)
 			down_write(&devnet_rename_sem);
 			memcpy(dev->name, oldname, IFNAMSIZ);
 			memcpy(oldname, newname, IFNAMSIZ);
-			dev->name_assign_type = old_assign_type;
+			WRITE_ONCE(dev->name_assign_type, old_assign_type);
 			old_assign_type = NET_NAME_RENAMED;
 			goto rollback;
 		} else {
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index a09d507c5b03d24a829bf7af0b7cf1e6a0bdb65a..f4c2b82674951bbeefd880ca22c54e6a32c9f988 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -125,7 +125,7 @@ static DEVICE_ATTR_RO(iflink);
 
 static ssize_t format_name_assign_type(const struct net_device *dev, char *buf)
 {
-	return sysfs_emit(buf, fmt_dec, dev->name_assign_type);
+	return sysfs_emit(buf, fmt_dec, READ_ONCE(dev->name_assign_type));
 }
 
 static ssize_t name_assign_type_show(struct device *dev,
@@ -135,7 +135,7 @@ static ssize_t name_assign_type_show(struct device *dev,
 	struct net_device *ndev = to_net_dev(dev);
 	ssize_t ret = -EINVAL;
 
-	if (ndev->name_assign_type != NET_NAME_UNKNOWN)
+	if (READ_ONCE(ndev->name_assign_type) != NET_NAME_UNKNOWN)
 		ret = netdev_show(dev, attr, buf, format_name_assign_type);
 
 	return ret;
-- 
2.43.0.687.g38aa6559b0-goog

[PATCH v3 net-next 02/13] ip_tunnel: annotate data-races around t->parms.link

[Eric Dumazet]

t->parms.link is read locklessly, annotate these reads
and opposite writes accordingly.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/ip_tunnel.c | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 00da0b80320fb514bca58de7cd13894ab49a2ca6..248eb2d9829b31f89b7700460e317bf88bf325d9 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -102,10 +102,9 @@ struct ip_tunnel *ip_tunnel_lookup(struct ip_tunnel_net *itn,
 		if (!ip_tunnel_key_match(&t->parms, flags, key))
 			continue;
 
-		if (t->parms.link == link)
+		if (READ_ONCE(t->parms.link) == link)
 			return t;
-		else
-			cand = t;
+		cand = t;
 	}
 
 	hlist_for_each_entry_rcu(t, head, hash_node) {
@@ -117,9 +116,9 @@ struct ip_tunnel *ip_tunnel_lookup(struct ip_tunnel_net *itn,
 		if (!ip_tunnel_key_match(&t->parms, flags, key))
 			continue;
 
-		if (t->parms.link == link)
+		if (READ_ONCE(t->parms.link) == link)
 			return t;
-		else if (!cand)
+		if (!cand)
 			cand = t;
 	}
 
@@ -137,9 +136,9 @@ struct ip_tunnel *ip_tunnel_lookup(struct ip_tunnel_net *itn,
 		if (!ip_tunnel_key_match(&t->parms, flags, key))
 			continue;
 
-		if (t->parms.link == link)
+		if (READ_ONCE(t->parms.link) == link)
 			return t;
-		else if (!cand)
+		if (!cand)
 			cand = t;
 	}
 
@@ -150,9 +149,9 @@ struct ip_tunnel *ip_tunnel_lookup(struct ip_tunnel_net *itn,
 		    !(t->dev->flags & IFF_UP))
 			continue;
 
-		if (t->parms.link == link)
+		if (READ_ONCE(t->parms.link) == link)
 			return t;
-		else if (!cand)
+		if (!cand)
 			cand = t;
 	}
 
@@ -221,7 +220,7 @@ static struct ip_tunnel *ip_tunnel_find(struct ip_tunnel_net *itn,
 	hlist_for_each_entry_rcu(t, head, hash_node) {
 		if (local == t->parms.iph.saddr &&
 		    remote == t->parms.iph.daddr &&
-		    link == t->parms.link &&
+		    link == READ_ONCE(t->parms.link) &&
 		    type == t->dev->type &&
 		    ip_tunnel_key_match(&t->parms, flags, key))
 			break;
@@ -747,7 +746,7 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
 
 	ip_tunnel_init_flow(&fl4, protocol, dst, tnl_params->saddr,
 			    tunnel->parms.o_key, RT_TOS(tos),
-			    dev_net(dev), tunnel->parms.link,
+			    dev_net(dev), READ_ONCE(tunnel->parms.link),
 			    tunnel->fwmark, skb_get_hash(skb), 0);
 
 	if (ip_tunnel_encap(skb, &tunnel->encap, &protocol, &fl4) < 0)
@@ -867,7 +866,7 @@ static void ip_tunnel_update(struct ip_tunnel_net *itn,
 	if (t->parms.link != p->link || t->fwmark != fwmark) {
 		int mtu;
 
-		t->parms.link = p->link;
+		WRITE_ONCE(t->parms.link, p->link);
 		t->fwmark = fwmark;
 		mtu = ip_tunnel_bind_dev(dev);
 		if (set_mtu)
@@ -1057,9 +1056,9 @@ EXPORT_SYMBOL(ip_tunnel_get_link_net);
 
 int ip_tunnel_get_iflink(const struct net_device *dev)
 {
-	struct ip_tunnel *tunnel = netdev_priv(dev);
+	const struct ip_tunnel *tunnel = netdev_priv(dev);
 
-	return tunnel->parms.link;
+	return READ_ONCE(tunnel->parms.link);
 }
 EXPORT_SYMBOL(ip_tunnel_get_iflink);
 
-- 
2.43.0.687.g38aa6559b0-goog

[PATCH v3 net-next 03/13] dev: annotate accesses to dev->link

[Eric Dumazet]

Following patch will read dev->link locklessly,
annotate the write from do_setlink().

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/core/rtnetlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 31f433950c8dc953bcb65cc0469f7df962314b87..8d95e0863534f80cecceb2dd4a7b2a16f7f4bca3 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2974,7 +2974,7 @@ static int do_setlink(const struct sk_buff *skb,
 		write_lock(&dev_base_lock);
 		if (dev->link_mode ^ value)
 			status |= DO_SETLINK_NOTIFY;
-		dev->link_mode = value;
+		WRITE_ONCE(dev->link_mode, value);
 		write_unlock(&dev_base_lock);
 	}
 
-- 
2.43.0.687.g38aa6559b0-goog

[PATCH v3 net-next 04/13] net: convert dev->reg_state to u8

[Eric Dumazet]

Prepares things so that dev->reg_state reads can be lockless,
by adding WRITE_ONCE() on write side.

READ_ONCE()/WRITE_ONCE() do not support bitfields.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/netdevice.h | 23 ++++++++++++++---------
 net/core/dev.c            |  8 ++++----
 2 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 07cefa32eafa93dd1a4602de892d0ee1cbf2e22b..24fd24b0f2341f662b28ade45ed12a5e6d02852a 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1815,6 +1815,15 @@ enum netdev_stat_type {
 	NETDEV_PCPU_STAT_DSTATS, /* struct pcpu_dstats */
 };
 
+enum netdev_reg_state {
+	NETREG_UNINITIALIZED = 0,
+	NETREG_REGISTERED,	/* completed register_netdevice */
+	NETREG_UNREGISTERING,	/* called unregister_netdevice */
+	NETREG_UNREGISTERED,	/* completed unregister todo */
+	NETREG_RELEASED,	/* called free_netdev */
+	NETREG_DUMMY,		/* dummy device for NAPI poll */
+};
+
 /**
  *	struct net_device - The DEVICE structure.
  *
@@ -2372,13 +2381,7 @@ struct net_device {
 
 	struct list_head	link_watch_list;
 
-	enum { NETREG_UNINITIALIZED=0,
-	       NETREG_REGISTERED,	/* completed register_netdevice */
-	       NETREG_UNREGISTERING,	/* called unregister_netdevice */
-	       NETREG_UNREGISTERED,	/* completed unregister todo */
-	       NETREG_RELEASED,		/* called free_netdev */
-	       NETREG_DUMMY,		/* dummy device for NAPI poll */
-	} reg_state:8;
+	u8 reg_state;
 
 	bool dismantle;
 
@@ -5254,7 +5257,9 @@ static inline const char *netdev_name(const struct net_device *dev)
 
 static inline const char *netdev_reg_state(const struct net_device *dev)
 {
-	switch (dev->reg_state) {
+	u8 reg_state = READ_ONCE(dev->reg_state);
+
+	switch (reg_state) {
 	case NETREG_UNINITIALIZED: return " (uninitialized)";
 	case NETREG_REGISTERED: return "";
 	case NETREG_UNREGISTERING: return " (unregistering)";
@@ -5263,7 +5268,7 @@ static inline const char *netdev_reg_state(const struct net_device *dev)
 	case NETREG_DUMMY: return " (dummy)";
 	}
 
-	WARN_ONCE(1, "%s: unknown reg_state %d\n", dev->name, dev->reg_state);
+	WARN_ONCE(1, "%s: unknown reg_state %d\n", dev->name, reg_state);
 	return " (unknown)";
 }
 
diff --git a/net/core/dev.c b/net/core/dev.c
index 7bba4a47231726d666348539538ae94eb248fc3a..7d9d43ce2cb779c922759224e2690e24acda77fd 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10297,7 +10297,7 @@ int register_netdevice(struct net_device *dev)
 
 	ret = netdev_register_kobject(dev);
 	write_lock(&dev_base_lock);
-	dev->reg_state = ret ? NETREG_UNREGISTERED : NETREG_REGISTERED;
+	WRITE_ONCE(dev->reg_state, ret ? NETREG_UNREGISTERED : NETREG_REGISTERED);
 	write_unlock(&dev_base_lock);
 	if (ret)
 		goto err_uninit_notify;
@@ -10588,7 +10588,7 @@ void netdev_run_todo(void)
 		}
 
 		write_lock(&dev_base_lock);
-		dev->reg_state = NETREG_UNREGISTERED;
+		WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERED);
 		write_unlock(&dev_base_lock);
 		linkwatch_sync_dev(dev);
 	}
@@ -11008,7 +11008,7 @@ void free_netdev(struct net_device *dev)
 	}
 
 	BUG_ON(dev->reg_state != NETREG_UNREGISTERED);
-	dev->reg_state = NETREG_RELEASED;
+	WRITE_ONCE(dev->reg_state, NETREG_RELEASED);
 
 	/* will free via device release */
 	put_device(&dev->dev);
@@ -11098,7 +11098,7 @@ void unregister_netdevice_many_notify(struct list_head *head,
 		/* And unlink it from device chain. */
 		write_lock(&dev_base_lock);
 		unlist_netdevice(dev, false);
-		dev->reg_state = NETREG_UNREGISTERING;
+		WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERING);
 		write_unlock(&dev_base_lock);
 	}
 	flush_all_backlogs();
-- 
2.43.0.687.g38aa6559b0-goog

[PATCH v3 net-next 05/13] net-sysfs: convert netdev_show() to RCU

[Eric Dumazet]

Make clear dev_isalive() can be called with RCU protection.

Then convert netdev_show() to RCU, to remove dev_base_lock
dependency.

Also add RCU to broadcast_show().

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/core/net-sysfs.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index f4c2b82674951bbeefd880ca22c54e6a32c9f988..678e4be690821c5cdb933f5e91af2247ebecb830 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -34,10 +34,10 @@ static const char fmt_dec[] = "%d\n";
 static const char fmt_ulong[] = "%lu\n";
 static const char fmt_u64[] = "%llu\n";
 
-/* Caller holds RTNL or dev_base_lock */
+/* Caller holds RTNL, RCU or dev_base_lock */
 static inline int dev_isalive(const struct net_device *dev)
 {
-	return dev->reg_state <= NETREG_REGISTERED;
+	return READ_ONCE(dev->reg_state) <= NETREG_REGISTERED;
 }
 
 /* use same locking rules as GIF* ioctl's */
@@ -48,10 +48,10 @@ static ssize_t netdev_show(const struct device *dev,
 	struct net_device *ndev = to_net_dev(dev);
 	ssize_t ret = -EINVAL;
 
-	read_lock(&dev_base_lock);
+	rcu_read_lock();
 	if (dev_isalive(ndev))
 		ret = (*format)(ndev, buf);
-	read_unlock(&dev_base_lock);
+	rcu_read_unlock();
 
 	return ret;
 }
@@ -60,7 +60,7 @@ static ssize_t netdev_show(const struct device *dev,
 #define NETDEVICE_SHOW(field, format_string)				\
 static ssize_t format_##field(const struct net_device *dev, char *buf)	\
 {									\
-	return sysfs_emit(buf, format_string, dev->field);		\
+	return sysfs_emit(buf, format_string, READ_ONCE(dev->field));		\
 }									\
 static ssize_t field##_show(struct device *dev,				\
 			    struct device_attribute *attr, char *buf)	\
@@ -161,10 +161,13 @@ static ssize_t broadcast_show(struct device *dev,
 			      struct device_attribute *attr, char *buf)
 {
 	struct net_device *ndev = to_net_dev(dev);
+	int ret = -EINVAL;
 
+	rcu_read_lock();
 	if (dev_isalive(ndev))
-		return sysfs_format_mac(buf, ndev->broadcast, ndev->addr_len);
-	return -EINVAL;
+		ret = sysfs_format_mac(buf, ndev->broadcast, ndev->addr_len);
+	rcu_read_unlock();
+	return ret;
 }
 static DEVICE_ATTR_RO(broadcast);
 
-- 
2.43.0.687.g38aa6559b0-goog

[PATCH v3 net-next 06/13] net-sysfs: use dev_addr_sem to remove races in address_show()

[Eric Dumazet]

Using dev_base_lock is not preventing from reading garbage.

Use dev_addr_sem instead.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/netdevice.h |  1 +
 net/core/dev.c            |  2 +-
 net/core/net-sysfs.c      | 10 +++++++---
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 24fd24b0f2341f662b28ade45ed12a5e6d02852a..28569f195a449700b6403006f70257b8194b516a 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -4031,6 +4031,7 @@ int dev_set_mac_address(struct net_device *dev, struct sockaddr *sa,
 			struct netlink_ext_ack *extack);
 int dev_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
 			     struct netlink_ext_ack *extack);
+extern struct rw_semaphore dev_addr_sem;
 int dev_get_mac_address(struct sockaddr *sa, struct net *net, char *dev_name);
 int dev_get_port_parent_id(struct net_device *dev,
 			   struct netdev_phys_item_id *ppid, bool recurse);
diff --git a/net/core/dev.c b/net/core/dev.c
index 7d9d43ce2cb779c922759224e2690e24acda77fd..0c158dd534f80c46e66c890628be9a876e85068a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8951,7 +8951,7 @@ int dev_set_mac_address(struct net_device *dev, struct sockaddr *sa,
 }
 EXPORT_SYMBOL(dev_set_mac_address);
 
-static DECLARE_RWSEM(dev_addr_sem);
+DECLARE_RWSEM(dev_addr_sem);
 
 int dev_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
 			     struct netlink_ext_ack *extack)
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 678e4be690821c5cdb933f5e91af2247ebecb830..23ef2df549c3036a702f3be1dca1eda14ee5e76f 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -142,17 +142,21 @@ static ssize_t name_assign_type_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(name_assign_type);
 
-/* use same locking rules as GIFHWADDR ioctl's */
+/* use same locking rules as GIFHWADDR ioctl's (dev_get_mac_address()) */
 static ssize_t address_show(struct device *dev, struct device_attribute *attr,
 			    char *buf)
 {
 	struct net_device *ndev = to_net_dev(dev);
 	ssize_t ret = -EINVAL;
 
-	read_lock(&dev_base_lock);
+	down_read(&dev_addr_sem);
+
+	rcu_read_lock();
 	if (dev_isalive(ndev))
 		ret = sysfs_format_mac(buf, ndev->dev_addr, ndev->addr_len);
-	read_unlock(&dev_base_lock);
+	rcu_read_unlock();
+
+	up_read(&dev_addr_sem);
 	return ret;
 }
 static DEVICE_ATTR_RO(address);
-- 
2.43.0.687.g38aa6559b0-goog

Re: [PATCH v3 net-next 06/13] net-sysfs: use dev_addr_sem to remove races in address_show()

[Jakub Kicinski]

On Fri,  9 Feb 2024 20:34:21 +0000 Eric Dumazet wrote:
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 24fd24b0f2341f662b28ade45ed12a5e6d02852a..28569f195a449700b6403006f70257b8194b516a 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -4031,6 +4031,7 @@ int dev_set_mac_address(struct net_device *dev, struct sockaddr *sa,
>  			struct netlink_ext_ack *extack);
>  int dev_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
>  			     struct netlink_ext_ack *extack);
> +extern struct rw_semaphore dev_addr_sem;

nit: this could potentially live in the net/core/dev.h header?

I could not spot any real problems but the series seems to not apply 
to net-next because of 4cd582ffa5a9a5d58e5bac9c5e55ca8eeabffddc
-- 
pw-bot: cr

Re: [PATCH v3 net-next 06/13] net-sysfs: use dev_addr_sem to remove races in address_show()

[Eric Dumazet]

On Tue, Feb 13, 2024 at 2:58 AM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Fri,  9 Feb 2024 20:34:21 +0000 Eric Dumazet wrote:
> > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > index 24fd24b0f2341f662b28ade45ed12a5e6d02852a..28569f195a449700b6403006f70257b8194b516a 100644
> > --- a/include/linux/netdevice.h
> > +++ b/include/linux/netdevice.h
> > @@ -4031,6 +4031,7 @@ int dev_set_mac_address(struct net_device *dev, struct sockaddr *sa,
> >                       struct netlink_ext_ack *extack);
> >  int dev_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
> >                            struct netlink_ext_ack *extack);
> > +extern struct rw_semaphore dev_addr_sem;
>
> nit: this could potentially live in the net/core/dev.h header?

SGTM, I am taking a look.

>
> I could not spot any real problems but the series seems to not apply
> to net-next because of 4cd582ffa5a9a5d58e5bac9c5e55ca8eeabffddc

Right, of course, I will rebase and send v4, thanks !

[PATCH v3 net-next 07/13] net-sysfs: convert dev->operstate reads to lockless ones

[Eric Dumazet]

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>
---
 net/bridge/br_netlink.c |  3 ++-
 net/core/link_watch.c   |  4 ++--
 net/core/net-sysfs.c    |  4 +---
 net/core/rtnetlink.c    |  4 ++--
 net/hsr/hsr_device.c    | 10 +++++-----
 net/ipv6/addrconf.c     |  2 +-
 6 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 5ad4abfcb7ba3960bf69613ae7975180ae48854b..2cf4fc756263992eefe6a3580410766fea0c2c1f 100644
--- 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 429571c258da7720baf387fef81081a56a655ef5..1b93e054c9a3cfcdd5d1251a9982d88a071abbaa 100644
--- 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 23ef2df549c3036a702f3be1dca1eda14ee5e76f..c5d164b8c6bfb53793f8422063c6281d6339b36e 100644
--- 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 8d95e0863534f80cecceb2dd4a7b2a16f7f4bca3..4e797326c88fe1e23ca66e82103176767fe5c32e 100644
--- 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 9d71b66183daf94e19945d75cfb5c33df6ce346c..be0e43f46556e028e675147e63c6b787aa72e894 100644
--- 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 d63f5d063f073cb53f52e187efdbd09b8f78d622..1122c9ef09f6210fc373d9678a9da1ec1a3e78fa 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5998,7 +5998,7 @@ 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)
-- 
2.43.0.687.g38aa6559b0-goog

[PATCH v3 net-next 08/13] net-sysfs: convert netstat_show() to RCU

[Eric Dumazet]

dev_get_stats() can be called from RCU, there is no need
to acquire dev_base_lock.

Change dev_isalive() comment to reflect we no longer use
dev_base_lock from net/core/net-sysfs.c

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/core/net-sysfs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index c5d164b8c6bfb53793f8422063c6281d6339b36e..946caefdd9599f631a73487e950305c978f8bc66 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -34,7 +34,7 @@ static const char fmt_dec[] = "%d\n";
 static const char fmt_ulong[] = "%lu\n";
 static const char fmt_u64[] = "%llu\n";
 
-/* Caller holds RTNL, RCU or dev_base_lock */
+/* Caller holds RTNL or RCU */
 static inline int dev_isalive(const struct net_device *dev)
 {
 	return READ_ONCE(dev->reg_state) <= NETREG_REGISTERED;
@@ -685,14 +685,14 @@ static ssize_t netstat_show(const struct device *d,
 	WARN_ON(offset > sizeof(struct rtnl_link_stats64) ||
 		offset % sizeof(u64) != 0);
 
-	read_lock(&dev_base_lock);
+	rcu_read_lock();
 	if (dev_isalive(dev)) {
 		struct rtnl_link_stats64 temp;
 		const struct rtnl_link_stats64 *stats = dev_get_stats(dev, &temp);
 
 		ret = sysfs_emit(buf, fmt_u64, *(u64 *)(((u8 *)stats) + offset));
 	}
-	read_unlock(&dev_base_lock);
+	rcu_read_unlock();
 	return ret;
 }
 
-- 
2.43.0.687.g38aa6559b0-goog

[PATCH v3 net-next 09/13] net: remove stale mentions of dev_base_lock in comments

[Eric Dumazet]

Change comments incorrectly mentioning dev_base_lock.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 Documentation/networking/netdevices.rst     | 4 ++--
 drivers/net/ethernet/cisco/enic/enic_main.c | 2 +-
 drivers/net/ethernet/nvidia/forcedeth.c     | 4 ++--
 drivers/net/ethernet/sfc/efx_common.c       | 2 +-
 drivers/net/ethernet/sfc/falcon/efx.c       | 2 +-
 drivers/net/ethernet/sfc/siena/efx_common.c | 2 +-
 6 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/Documentation/networking/netdevices.rst b/Documentation/networking/netdevices.rst
index 9e4cccb90b8700aea49bb586ca0da79f2fe185b9..c2476917a6c37d9b87e8b5d59f2e00fa0a30e26a 100644
--- a/Documentation/networking/netdevices.rst
+++ b/Documentation/networking/netdevices.rst
@@ -252,8 +252,8 @@ ndo_eth_ioctl:
 	Context: process
 
 ndo_get_stats:
-	Synchronization: rtnl_lock() semaphore, dev_base_lock rwlock, or RCU.
-	Context: atomic (can't sleep under rwlock or RCU)
+	Synchronization: rtnl_lock() semaphore, or RCU.
+	Context: atomic (can't sleep under RCU)
 
 ndo_start_xmit:
 	Synchronization: __netif_tx_lock spinlock.
diff --git a/drivers/net/ethernet/cisco/enic/enic_main.c b/drivers/net/ethernet/cisco/enic/enic_main.c
index 37bd38d772e80967e50342f8b87dfa331192c5a0..d266a87297a5e3a5281acda9243a024fc2f7d742 100644
--- a/drivers/net/ethernet/cisco/enic/enic_main.c
+++ b/drivers/net/ethernet/cisco/enic/enic_main.c
@@ -872,7 +872,7 @@ static netdev_tx_t enic_hard_start_xmit(struct sk_buff *skb,
 	return NETDEV_TX_OK;
 }
 
-/* dev_base_lock rwlock held, nominally process context */
+/* rcu_read_lock potentially held, nominally process context */
 static void enic_get_stats(struct net_device *netdev,
 			   struct rtnl_link_stats64 *net_stats)
 {
diff --git a/drivers/net/ethernet/nvidia/forcedeth.c b/drivers/net/ethernet/nvidia/forcedeth.c
index 7a549b834e970a5ac40330513e3220466d78acef..31f896c4aa266032cbabdd3c0086eae5969d203a 100644
--- a/drivers/net/ethernet/nvidia/forcedeth.c
+++ b/drivers/net/ethernet/nvidia/forcedeth.c
@@ -1761,7 +1761,7 @@ static void nv_get_stats(int cpu, struct fe_priv *np,
 /*
  * nv_get_stats64: dev->ndo_get_stats64 function
  * Get latest stats value from the nic.
- * Called with read_lock(&dev_base_lock) held for read -
+ * Called with rcu_read_lock() held -
  * only synchronized against unregister_netdevice.
  */
 static void
@@ -3090,7 +3090,7 @@ static void set_bufsize(struct net_device *dev)
 
 /*
  * nv_change_mtu: dev->change_mtu function
- * Called with dev_base_lock held for read.
+ * Called with RTNL held for read.
  */
 static int nv_change_mtu(struct net_device *dev, int new_mtu)
 {
diff --git a/drivers/net/ethernet/sfc/efx_common.c b/drivers/net/ethernet/sfc/efx_common.c
index 175bd9cdfdac3ac8183e52f2e76b99839b9c2ed7..551f890db90a609319dca95af9b464bddb252121 100644
--- a/drivers/net/ethernet/sfc/efx_common.c
+++ b/drivers/net/ethernet/sfc/efx_common.c
@@ -595,7 +595,7 @@ void efx_stop_all(struct efx_nic *efx)
 	efx_stop_datapath(efx);
 }
 
-/* Context: process, dev_base_lock or RTNL held, non-blocking. */
+/* Context: process, rcu_read_lock or RTNL held, non-blocking. */
 void efx_net_stats(struct net_device *net_dev, struct rtnl_link_stats64 *stats)
 {
 	struct efx_nic *efx = efx_netdev_priv(net_dev);
diff --git a/drivers/net/ethernet/sfc/falcon/efx.c b/drivers/net/ethernet/sfc/falcon/efx.c
index e001f27085c6614374a0e5e1493b215d6c55e9db..1cb32aedd89c7393c7881efb11963cf334bca3ae 100644
--- a/drivers/net/ethernet/sfc/falcon/efx.c
+++ b/drivers/net/ethernet/sfc/falcon/efx.c
@@ -2085,7 +2085,7 @@ int ef4_net_stop(struct net_device *net_dev)
 	return 0;
 }
 
-/* Context: process, dev_base_lock or RTNL held, non-blocking. */
+/* Context: process, rcu_read_lock or RTNL held, non-blocking. */
 static void ef4_net_stats(struct net_device *net_dev,
 			  struct rtnl_link_stats64 *stats)
 {
diff --git a/drivers/net/ethernet/sfc/siena/efx_common.c b/drivers/net/ethernet/sfc/siena/efx_common.c
index e4b294b8e9acb15f68b6597047d493add699196f..88e5bc347a44cea66e36dcc6afe10ef10c1383fa 100644
--- a/drivers/net/ethernet/sfc/siena/efx_common.c
+++ b/drivers/net/ethernet/sfc/siena/efx_common.c
@@ -605,7 +605,7 @@ static size_t efx_siena_update_stats_atomic(struct efx_nic *efx, u64 *full_stats
 	return efx->type->update_stats(efx, full_stats, core_stats);
 }
 
-/* Context: process, dev_base_lock or RTNL held, non-blocking. */
+/* Context: process, rcu_read_lock or RTNL held, non-blocking. */
 void efx_siena_net_stats(struct net_device *net_dev,
 			 struct rtnl_link_stats64 *stats)
 {
-- 
2.43.0.687.g38aa6559b0-goog

[PATCH v3 net-next 10/13] net: add netdev_set_operstate() helper

[Eric Dumazet]

dev_base_lock is going away, add netdev_set_operstate() helper
so that hsr does not have to know core internals.

Remove dev_base_lock acquisition from rfc2863_policy()

v3: use an "unsigned int" for dev->operstate,
    so that try_cmpxchg() can work on all arches.
        ( https://lore.kernel.org/oe-kbuild-all/202402081918.OLyGaea3-lkp@intel.com/ )

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/netdevice.h |  2 +-
 include/linux/rtnetlink.h |  2 ++
 net/core/link_watch.c     |  9 ++-------
 net/core/rtnetlink.c      | 22 +++++++++++++++-------
 net/hsr/hsr_device.c      | 22 ++++++----------------
 5 files changed, 26 insertions(+), 31 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 28569f195a449700b6403006f70257b8194b516a..d4d1e438ab8f1d2bd6426837b504ad6891fe83b7 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2258,7 +2258,7 @@ struct net_device {
 	const struct tlsdev_ops *tlsdev_ops;
 #endif
 
-	unsigned char		operstate;
+	unsigned int		operstate;
 	unsigned char		link_mode;
 
 	unsigned char		if_port;
diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 21780608cf47ca0687dbaaf0d07b561e8631412c..cdfc897f1e3c683940a0958bc8a790c07ae819b0 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -172,4 +172,6 @@ rtnl_notify_needed(const struct net *net, u16 nlflags, u32 group)
 	return (nlflags & NLM_F_ECHO) || rtnl_has_listeners(net, group);
 }
 
+void netdev_set_operstate(struct net_device *dev, int newstate);
+
 #endif	/* __LINUX_RTNETLINK_H */
diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index 1b93e054c9a3cfcdd5d1251a9982d88a071abbaa..8ec35194bfcb8574f53a9fd28f0cb2ebfe9a3f2e 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -33,7 +33,7 @@ static DECLARE_DELAYED_WORK(linkwatch_work, linkwatch_event);
 static LIST_HEAD(lweventlist);
 static DEFINE_SPINLOCK(lweventlist_lock);
 
-static unsigned char default_operstate(const struct net_device *dev)
+static unsigned int default_operstate(const struct net_device *dev)
 {
 	if (netif_testing(dev))
 		return IF_OPER_TESTING;
@@ -62,16 +62,13 @@ static unsigned char default_operstate(const struct net_device *dev)
 	return IF_OPER_UP;
 }
 
-
 static void rfc2863_policy(struct net_device *dev)
 {
-	unsigned char operstate = default_operstate(dev);
+	unsigned int operstate = default_operstate(dev);
 
 	if (operstate == READ_ONCE(dev->operstate))
 		return;
 
-	write_lock(&dev_base_lock);
-
 	switch(dev->link_mode) {
 	case IF_LINK_MODE_TESTING:
 		if (operstate == IF_OPER_UP)
@@ -88,8 +85,6 @@ static void rfc2863_policy(struct net_device *dev)
 	}
 
 	WRITE_ONCE(dev->operstate, operstate);
-
-	write_unlock(&dev_base_lock);
 }
 
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 4e797326c88fe1e23ca66e82103176767fe5c32e..16634c6b1f2b9c0d818bb757c8428039c3f3320f 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -842,9 +842,22 @@ int rtnl_put_cacheinfo(struct sk_buff *skb, struct dst_entry *dst, u32 id,
 }
 EXPORT_SYMBOL_GPL(rtnl_put_cacheinfo);
 
+void netdev_set_operstate(struct net_device *dev, int newstate)
+{
+	unsigned int old = READ_ONCE(dev->operstate);
+
+	do {
+		if (old == newstate)
+			return;
+	} while (!try_cmpxchg(&dev->operstate, &old, newstate));
+
+	netdev_state_change(dev);
+}
+EXPORT_SYMBOL(netdev_set_operstate);
+
 static void set_operstate(struct net_device *dev, unsigned char transition)
 {
-	unsigned char operstate = dev->operstate;
+	unsigned char operstate = READ_ONCE(dev->operstate);
 
 	switch (transition) {
 	case IF_OPER_UP:
@@ -866,12 +879,7 @@ static void set_operstate(struct net_device *dev, unsigned char transition)
 		break;
 	}
 
-	if (READ_ONCE(dev->operstate) != operstate) {
-		write_lock(&dev_base_lock);
-		WRITE_ONCE(dev->operstate, operstate);
-		write_unlock(&dev_base_lock);
-		netdev_state_change(dev);
-	}
+	netdev_set_operstate(dev, operstate);
 }
 
 static unsigned int rtnl_dev_get_flags(const struct net_device *dev)
diff --git a/net/hsr/hsr_device.c b/net/hsr/hsr_device.c
index be0e43f46556e028e675147e63c6b787aa72e894..5ef6d437db727e60bfd8cf68f010f0151d0db98b 100644
--- a/net/hsr/hsr_device.c
+++ b/net/hsr/hsr_device.c
@@ -28,29 +28,19 @@ static bool is_slave_up(struct net_device *dev)
 	return dev && is_admin_up(dev) && netif_oper_up(dev);
 }
 
-static void __hsr_set_operstate(struct net_device *dev, int transition)
-{
-	write_lock(&dev_base_lock);
-	if (READ_ONCE(dev->operstate) != transition) {
-		WRITE_ONCE(dev->operstate, transition);
-		write_unlock(&dev_base_lock);
-		netdev_state_change(dev);
-	} else {
-		write_unlock(&dev_base_lock);
-	}
-}
-
 static void hsr_set_operstate(struct hsr_port *master, bool has_carrier)
 {
-	if (!is_admin_up(master->dev)) {
-		__hsr_set_operstate(master->dev, IF_OPER_DOWN);
+	struct net_device *dev = master->dev;
+
+	if (!is_admin_up(dev)) {
+		netdev_set_operstate(dev, IF_OPER_DOWN);
 		return;
 	}
 
 	if (has_carrier)
-		__hsr_set_operstate(master->dev, IF_OPER_UP);
+		netdev_set_operstate(dev, IF_OPER_UP);
 	else
-		__hsr_set_operstate(master->dev, IF_OPER_LOWERLAYERDOWN);
+		netdev_set_operstate(dev, IF_OPER_LOWERLAYERDOWN);
 }
 
 static bool hsr_check_carrier(struct hsr_port *master)
-- 
2.43.0.687.g38aa6559b0-goog

[PATCH v3 net-next 11/13] net: remove dev_base_lock from do_setlink()

[Eric Dumazet]

We hold RTNL here, and dev->link_mode readers already
are using READ_ONCE().

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/core/rtnetlink.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 16634c6b1f2b9c0d818bb757c8428039c3f3320f..c2e3d8db8b013585dea62d8fbb0728a85ccac952 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2979,11 +2979,9 @@ static int do_setlink(const struct sk_buff *skb,
 	if (tb[IFLA_LINKMODE]) {
 		unsigned char value = nla_get_u8(tb[IFLA_LINKMODE]);
 
-		write_lock(&dev_base_lock);
 		if (dev->link_mode ^ value)
 			status |= DO_SETLINK_NOTIFY;
 		WRITE_ONCE(dev->link_mode, value);
-		write_unlock(&dev_base_lock);
 	}
 
 	if (tb[IFLA_VFINFO_LIST]) {
-- 
2.43.0.687.g38aa6559b0-goog

[PATCH v3 net-next 12/13] net: remove dev_base_lock from register_netdevice() and friends.

[Eric Dumazet]

RTNL already protects writes to dev->reg_state, we no longer need to hold
dev_base_lock to protect the readers.

unlist_netdevice() second argument can be removed.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/core/dev.c | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 0c158dd534f80c46e66c890628be9a876e85068a..a1cb7d3cab2c521fc28bd5f522c147bffca8d15e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -412,7 +412,7 @@ static void list_netdevice(struct net_device *dev)
 /* Device list removal
  * caller must respect a RCU grace period before freeing/reusing dev
  */
-static void unlist_netdevice(struct net_device *dev, bool lock)
+static void unlist_netdevice(struct net_device *dev)
 {
 	struct netdev_name_node *name_node;
 	struct net *net = dev_net(dev);
@@ -425,13 +425,11 @@ static void unlist_netdevice(struct net_device *dev, bool lock)
 		netdev_name_node_del(name_node);
 
 	/* Unlink dev from the device chain */
-	if (lock)
-		write_lock(&dev_base_lock);
+	write_lock(&dev_base_lock);
 	list_del_rcu(&dev->dev_list);
 	netdev_name_node_del(dev->name_node);
 	hlist_del_rcu(&dev->index_hlist);
-	if (lock)
-		write_unlock(&dev_base_lock);
+	write_unlock(&dev_base_lock);
 
 	dev_base_seq_inc(dev_net(dev));
 }
@@ -10296,9 +10294,9 @@ int register_netdevice(struct net_device *dev)
 		goto err_ifindex_release;
 
 	ret = netdev_register_kobject(dev);
-	write_lock(&dev_base_lock);
+
 	WRITE_ONCE(dev->reg_state, ret ? NETREG_UNREGISTERED : NETREG_REGISTERED);
-	write_unlock(&dev_base_lock);
+
 	if (ret)
 		goto err_uninit_notify;
 
@@ -10587,9 +10585,7 @@ void netdev_run_todo(void)
 			continue;
 		}
 
-		write_lock(&dev_base_lock);
 		WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERED);
-		write_unlock(&dev_base_lock);
 		linkwatch_sync_dev(dev);
 	}
 
@@ -11096,10 +11092,8 @@ void unregister_netdevice_many_notify(struct list_head *head,
 
 	list_for_each_entry(dev, head, unreg_list) {
 		/* And unlink it from device chain. */
-		write_lock(&dev_base_lock);
-		unlist_netdevice(dev, false);
+		unlist_netdevice(dev);
 		WRITE_ONCE(dev->reg_state, NETREG_UNREGISTERING);
-		write_unlock(&dev_base_lock);
 	}
 	flush_all_backlogs();
 
@@ -11281,7 +11275,7 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 	dev_close(dev);
 
 	/* And unlink it from device chain */
-	unlist_netdevice(dev, true);
+	unlist_netdevice(dev);
 
 	synchronize_net();
 
-- 
2.43.0.687.g38aa6559b0-goog

[PATCH v3 net-next 13/13] net: remove dev_base_lock

[Eric Dumazet]

dev_base_lock is not needed anymore, all remaining users also hold RTNL.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/netdevice.h |  2 --
 net/core/dev.c            | 39 ++++-----------------------------------
 2 files changed, 4 insertions(+), 37 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index d4d1e438ab8f1d2bd6426837b504ad6891fe83b7..94968baa7da172b69cc8ac148d39315018893420 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3077,8 +3077,6 @@ int call_netdevice_notifiers(unsigned long val, struct net_device *dev);
 int call_netdevice_notifiers_info(unsigned long val,
 				  struct netdev_notifier_info *info);
 
-extern rwlock_t				dev_base_lock;		/* Device list lock */
-
 #define for_each_netdev(net, d)		\
 		list_for_each_entry(d, &(net)->dev_base_head, dev_list)
 #define for_each_netdev_reverse(net, d)	\
diff --git a/net/core/dev.c b/net/core/dev.c
index a1cb7d3cab2c521fc28bd5f522c147bffca8d15e..456877e4b5d165878b3886db56d934c9e8c9cedc 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -166,28 +166,6 @@ static int call_netdevice_notifiers_extack(unsigned long val,
 					   struct net_device *dev,
 					   struct netlink_ext_ack *extack);
 
-/*
- * The @dev_base_head list is protected by @dev_base_lock and the rtnl
- * semaphore.
- *
- * Pure readers hold dev_base_lock for reading, or rcu_read_lock()
- *
- * Writers must hold the rtnl semaphore while they loop through the
- * dev_base_head list, and hold dev_base_lock for writing when they do the
- * actual updates.  This allows pure readers to access the list even
- * while a writer is preparing to update it.
- *
- * To put it another way, dev_base_lock is held for writing only to
- * protect against pure readers; the rtnl semaphore provides the
- * protection against other writers.
- *
- * See, for example usages, register_netdevice() and
- * unregister_netdevice(), which must be called with the rtnl
- * semaphore held.
- */
-DEFINE_RWLOCK(dev_base_lock);
-EXPORT_SYMBOL(dev_base_lock);
-
 static DEFINE_MUTEX(ifalias_mutex);
 
 /* protects napi_hash addition/deletion and napi_gen_id */
@@ -393,12 +371,10 @@ static void list_netdevice(struct net_device *dev)
 
 	ASSERT_RTNL();
 
-	write_lock(&dev_base_lock);
 	list_add_tail_rcu(&dev->dev_list, &net->dev_base_head);
 	netdev_name_node_add(net, dev->name_node);
 	hlist_add_head_rcu(&dev->index_hlist,
 			   dev_index_hash(net, dev->ifindex));
-	write_unlock(&dev_base_lock);
 
 	netdev_for_each_altname(dev, name_node)
 		netdev_name_node_add(net, name_node);
@@ -425,11 +401,9 @@ static void unlist_netdevice(struct net_device *dev)
 		netdev_name_node_del(name_node);
 
 	/* Unlink dev from the device chain */
-	write_lock(&dev_base_lock);
 	list_del_rcu(&dev->dev_list);
 	netdev_name_node_del(dev->name_node);
 	hlist_del_rcu(&dev->index_hlist);
-	write_unlock(&dev_base_lock);
 
 	dev_base_seq_inc(dev_net(dev));
 }
@@ -744,9 +718,9 @@ EXPORT_SYMBOL_GPL(dev_fill_forward_path);
  *	@net: the applicable net namespace
  *	@name: name to find
  *
- *	Find an interface by name. Must be called under RTNL semaphore
- *	or @dev_base_lock. If the name is found a pointer to the device
- *	is returned. If the name is not found then %NULL is returned. The
+ *	Find an interface by name. Must be called under RTNL semaphore.
+ *	If the name is found a pointer to the device is returned.
+ *	If the name is not found then %NULL is returned. The
  *	reference counters are not incremented so the caller must be
  *	careful with locks.
  */
@@ -827,8 +801,7 @@ EXPORT_SYMBOL(netdev_get_by_name);
  *	Search for an interface by index. Returns %NULL if the device
  *	is not found or a pointer to the device. The device has not
  *	had its reference counter increased so the caller must be careful
- *	about locking. The caller must hold either the RTNL semaphore
- *	or @dev_base_lock.
+ *	about locking. The caller must hold the RTNL semaphore.
  */
 
 struct net_device *__dev_get_by_index(struct net *net, int ifindex)
@@ -1233,15 +1206,11 @@ int dev_change_name(struct net_device *dev, const char *newname)
 
 	netdev_adjacent_rename_links(dev, oldname);
 
-	write_lock(&dev_base_lock);
 	netdev_name_node_del(dev->name_node);
-	write_unlock(&dev_base_lock);
 
 	synchronize_rcu();
 
-	write_lock(&dev_base_lock);
 	netdev_name_node_add(net, dev->name_node);
-	write_unlock(&dev_base_lock);
 
 	ret = call_netdevice_notifiers(NETDEV_CHANGENAME, dev);
 	ret = notifier_to_errno(ret);
-- 
2.43.0.687.g38aa6559b0-goog