[NET]: Move dev_base and dev_base_lock into net/core/dev.c

1 files changed, 25 insertions, 0 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 55fbdfa556c1..e298f2b7f9c9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -161,6 +161,31 @@ static struct timer_list samp_timer = TIMER_INITIALIZER(sample_queue, 0, 0);
 #endif
 
 /*
+ * The @dev_base list is protected by @dev_base_lock and the rtln
+ * semaphore.
+ *
+ * Pure readers hold dev_base_lock for reading.
+ *
+ * Writers must hold the rtnl semaphore while they loop through the
+ * dev_base 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.
+ */
+struct net_device *dev_base;
+rwlock_t dev_base_lock = RW_LOCK_UNLOCKED;
+
+EXPORT_SYMBOL(dev_base);
+EXPORT_SYMBOL(dev_base_lock);
+
+/*
  *	Our notifier list
  */