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Message-ID: <20250324224537.248800-7-kuba@kernel.org>
Date: Mon, 24 Mar 2025 15:45:32 -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 06/11] net: designate queue -> napi linking as "ops protected"
netdev netlink is the only reader of netdev_{,rx_}queue->napi,
and it already holds netdev->lock. Switch protection of
the writes to netdev->lock to "ops protected".
The expectation will be now that accessing queue->napi
will require netdev->lock for "ops locked" drivers, and
rtnl_lock for all other drivers.
Current "ops locked" drivers don't require any changes.
gve and netdevsim use _locked() helpers right next to
netif_queue_set_napi() so they must be holding the instance
lock. iavf doesn't call it. bnxt is a bit messy but all paths
seem locked.
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
include/linux/netdevice.h | 5 +++--
include/net/netdev_lock.h | 8 ++++++++
include/net/netdev_rx_queue.h | 2 +-
net/core/dev.c | 3 +--
4 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 3dbce9cd3f5a..fd508e9f148c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -710,7 +710,7 @@ struct netdev_queue {
* slow- / control-path part
*/
/* NAPI instance for the queue
- * Readers and writers must hold RTNL
+ * "ops protected", see comment about net_device::lock
*/
struct napi_struct *napi;
@@ -2522,7 +2522,8 @@ struct net_device {
* Double ops protects:
* @real_num_rx_queues, @real_num_tx_queues
*
- * Also protects some fields in struct napi_struct.
+ * Also protects some fields in:
+ * struct napi_struct, struct netdev_queue, struct netdev_rx_queue
*
* Ordering: take after rtnl_lock.
*/
diff --git a/include/net/netdev_lock.h b/include/net/netdev_lock.h
index efd302375ef2..1c0c9a94cc22 100644
--- a/include/net/netdev_lock.h
+++ b/include/net/netdev_lock.h
@@ -56,6 +56,14 @@ static inline void netdev_ops_assert_locked(const struct net_device *dev)
ASSERT_RTNL();
}
+static inline void
+netdev_ops_assert_locked_or_invisible(const struct net_device *dev)
+{
+ if (dev->reg_state == NETREG_REGISTERED ||
+ dev->reg_state == NETREG_UNREGISTERING)
+ netdev_ops_assert_locked(dev);
+}
+
static inline int netdev_lock_cmp_fn(const struct lockdep_map *a,
const struct lockdep_map *b)
{
diff --git a/include/net/netdev_rx_queue.h b/include/net/netdev_rx_queue.h
index af40842f229d..b2238b551dce 100644
--- a/include/net/netdev_rx_queue.h
+++ b/include/net/netdev_rx_queue.h
@@ -24,7 +24,7 @@ struct netdev_rx_queue {
struct xsk_buff_pool *pool;
#endif
/* NAPI instance for the queue
- * Readers and writers must hold RTNL
+ * "ops protected", see comment about net_device::lock
*/
struct napi_struct *napi;
struct pp_memory_provider_params mp_params;
diff --git a/net/core/dev.c b/net/core/dev.c
index aa99c91fd68f..690d46497b2f 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6896,8 +6896,7 @@ void netif_queue_set_napi(struct net_device *dev, unsigned int queue_index,
if (WARN_ON_ONCE(napi && !napi->dev))
return;
- if (dev->reg_state >= NETREG_REGISTERED)
- ASSERT_RTNL();
+ netdev_ops_assert_locked_or_invisible(dev);
switch (type) {
case NETDEV_QUEUE_TYPE_RX:
--
2.49.0
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