netdev - [PATCH net-next 04/13] net: convert dev->reg

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Message-ID: <20240207142629.3456570-5-edumazet@google.com>
Date: Wed,  7 Feb 2024 14:26:20 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 04/13] net: convert dev->reg_state to u8

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

Signed-off-by: Eric Dumazet <edumazet@...gle.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 118c40258d07b787adf518e576e75545e4bae846..bed8de91e91a4bd83fe80f6835643af68f1adc53 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 d2321a68a8abb4a4253c5843952b542ed040327a..027d0b7976f337df885266aeab2c90fe631decf1 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10268,7 +10268,7 @@ 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;
@@ -10561,7 +10561,7 @@ 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);
 	}
@@ -10981,7 +10981,7 @@ 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);
@@ -11071,7 +11071,7 @@ 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();
-- 
2.43.0.594.gd9cf4e227d-goog