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Message-ID: <20250408195956.412733-8-kuba@kernel.org> Date: Tue, 8 Apr 2025 12:59:54 -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, hramamurthy@...gle.com, kuniyu@...zon.com, jdamato@...tly.com, Jakub Kicinski <kuba@...nel.org> Subject: [PATCH net-next v2 7/8] docs: netdev: break down the instance locking info per ops struct Explicitly list all the ops structs and what locking they provide. Use "ops locked" as a term for drivers which have ops called under the instance lock. Acked-by: Stanislav Fomichev <sdf@...ichev.me> Signed-off-by: Jakub Kicinski <kuba@...nel.org> --- v2: - an exception -> exceptions v1: https://lore.kernel.org/20250407190117.16528-8-kuba@kernel.org --- Documentation/networking/netdevices.rst | 54 +++++++++++++++++++------ 1 file changed, 42 insertions(+), 12 deletions(-) diff --git a/Documentation/networking/netdevices.rst b/Documentation/networking/netdevices.rst index d6357472d3f1..7ae28c5fb835 100644 --- a/Documentation/networking/netdevices.rst +++ b/Documentation/networking/netdevices.rst @@ -314,13 +314,8 @@ struct napi_struct synchronization rules softirq will be called with interrupts disabled by netconsole. -struct netdev_queue_mgmt_ops synchronization rules -================================================== - -All queue management ndo callbacks are holding netdev instance lock. - -RTNL and netdev instance lock -============================= +netdev instance lock +==================== Historically, all networking control operations were protected by a single global lock known as ``rtnl_lock``. There is an ongoing effort to replace this @@ -328,10 +323,13 @@ global lock with separate locks for each network namespace. Additionally, properties of individual netdev are increasingly protected by per-netdev locks. For device drivers that implement shaping or queue management APIs, all control -operations will be performed under the netdev instance lock. Currently, this -instance lock is acquired within the context of ``rtnl_lock``. The drivers -can also explicitly request instance lock to be acquired via -``request_ops_lock``. In the future, there will be an option for individual +operations will be performed under the netdev instance lock. +Drivers can also explicitly request instance lock to be held during ops +by setting ``request_ops_lock`` to true. Code comments and docs refer +to drivers which have ops called under the instance lock as "ops locked". +See also the documentation of the ``lock`` member of struct net_device. + +In the future, there will be an option for individual drivers to opt out of using ``rtnl_lock`` and instead perform their control operations directly under the netdev instance lock. @@ -343,8 +341,40 @@ there are two sets of interfaces: ``dev_xxx`` and ``netif_xxx`` (e.g., acquiring the instance lock themselves, while the ``netif_xxx`` functions assume that the driver has already acquired the instance lock. +struct net_device_ops +--------------------- + +``ndos`` are called without holding the instance lock for most drivers. + +"Ops locked" drivers will have most of the ``ndos`` invoked under +the instance lock. + +struct ethtool_ops +------------------ + +Similarly to ``ndos`` the instance lock is only held for select drivers. +For "ops locked" drivers all ethtool ops without exceptions should +be called under the instance lock. + +struct net_shaper_ops +--------------------- + +All net shaper callbacks are invoked while holding the netdev instance +lock. ``rtnl_lock`` may or may not be held. + +Note that supporting net shapers automatically enables "ops locking". + +struct netdev_queue_mgmt_ops +---------------------------- + +All queue management callbacks are invoked while holding the netdev instance +lock. ``rtnl_lock`` may or may not be held. + +Note that supporting struct netdev_queue_mgmt_ops automatically enables +"ops locking". + Notifiers and netdev instance lock -================================== +---------------------------------- For device drivers that implement shaping or queue management APIs, some of the notifiers (``enum netdev_cmd``) are running under the netdev -- 2.49.0
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