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Message-ID: <20250324224537.248800-5-kuba@kernel.org>
Date: Mon, 24 Mar 2025 15:45:30 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
edumazet@...gle.com,
pabeni@...hat.com,
andrew+netdev@...n.ch,
horms@...nel.org,
sdf@...ichev.me,
Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net-next v2 04/11] net: explain "protection types" for the instance lock
Try to define some terminology for which fields are protected
by which lock and how. Some fields are protected by both rtnl_lock
and instance lock which is hard to talk about without having
a "key phrase" to refer to a particular protection scheme.
"ops protected" fields are defined later in the series, one by one.
Add ASSERT_RTNL() to netdev_ops_assert_locked() for drivers
not other instance protection of ops. Hopefully it's not too
confusion that netdev_lock_ops() does not match the lock which
netdev_ops_assert_locked() will assert, exactly. The noun "ops"
is in a different place in the name, so I think it's acceptable...
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
include/linux/netdevice.h | 24 ++++++++++++++++++------
include/net/netdev_lock.h | 3 +++
2 files changed, 21 insertions(+), 6 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 55859c565f84..09773e5c109a 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2496,19 +2496,31 @@ struct net_device {
* Should always be taken using netdev_lock() / netdev_unlock() helpers.
* Drivers are free to use it for other protection.
*
- * Protects:
+ * For the drivers that implement shaper or queue API, the scope
+ * of this lock is expanded to cover most ndo/queue/ethtool/sysfs
+ * operations. Drivers may opt-in to this behavior by setting
+ * @request_ops_lock.
+ *
+ * @lock protection mixes with rtnl_lock in multiple ways, fields are
+ * either:
+ * - simply protected by the instance @lock;
+ * - double protected - writers hold both locks, readers hold either;
+ * - ops protected - protected by the lock held around the NDOs
+ * and other callbacks, that is the instance lock on devices for
+ * which netdev_need_ops_lock() returns true, otherwise by rtnl_lock;
+ * - double ops protected - always protected by rtnl_lock but for
+ * devices for which netdev_need_ops_lock() returns true - also
+ * the instance lock.
+ *
+ * Simply protects:
* @gro_flush_timeout, @napi_defer_hard_irqs, @napi_list,
* @net_shaper_hierarchy, @reg_state, @threaded
*
- * Partially protects (writers must hold both @lock and rtnl_lock):
+ * Double protects:
* @up
*
* Also protects some fields in struct napi_struct.
*
- * For the drivers that implement shaper or queue API, the scope
- * of this lock is expanded to cover most ndo/queue/ethtool/sysfs
- * operations.
- *
* Ordering: take after rtnl_lock.
*/
struct mutex lock;
diff --git a/include/net/netdev_lock.h b/include/net/netdev_lock.h
index 689ffdfae50d..efd302375ef2 100644
--- a/include/net/netdev_lock.h
+++ b/include/net/netdev_lock.h
@@ -5,6 +5,7 @@
#include <linux/lockdep.h>
#include <linux/netdevice.h>
+#include <linux/rtnetlink.h>
static inline bool netdev_trylock(struct net_device *dev)
{
@@ -51,6 +52,8 @@ static inline void netdev_ops_assert_locked(const struct net_device *dev)
{
if (netdev_need_ops_lock(dev))
lockdep_assert_held(&dev->lock);
+ else
+ ASSERT_RTNL();
}
static inline int netdev_lock_cmp_fn(const struct lockdep_map *a,
--
2.49.0
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