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Vlad Buslov says: ==================== Refactor cls hardware offload API to support rtnl-independent drivers Currently, all cls API hardware offloads driver callbacks require caller to hold rtnl lock when calling them. This patch set introduces new API that allows drivers to register callbacks that are not dependent on rtnl lock and unlocked classifiers to offload filters without obtaining rtnl lock first, which is intended to allow offloading tc rules in parallel. Recently, new rtnl registration flag RTNL_FLAG_DOIT_UNLOCKED was added. TC rule update handlers (RTM_NEWTFILTER, RTM_DELTFILTER, etc.) are already registered with this flag and only take rtnl lock when qdisc or classifier requires it. Classifiers can indicate that their ops callbacks don't require caller to hold rtnl lock by setting the TCF_PROTO_OPS_DOIT_UNLOCKED flag. Unlocked implementation of flower classifier is now upstreamed. However, this implementation still obtains rtnl lock before calling hardware offloads API. Implement following cls API changes: - Introduce new "unlocked_driver_cb" flag to struct flow_block_offload to allow registering and unregistering block hardware offload callbacks that do not require caller to hold rtnl lock. Drivers that doesn't require users of its tc offload callbacks to hold rtnl lock sets the flag to true on block bind/unbind. Internally tcf_block is extended with additional lockeddevcnt counter that is used to count number of devices that require rtnl lock that block is bound to. When this counter is zero, tc_setup_cb_*() functions execute callbacks without obtaining rtnl lock. - Extend cls API single hardware rule update tc_setup_cb_call() function with tc_setup_cb_add(), tc_setup_cb_replace(), tc_setup_cb_destroy() and tc_setup_cb_reoffload() functions. These new APIs are needed to move management of block offload counter, filter in hardware counter and flag from classifier implementations to cls API, which is now responsible for managing them in concurrency-safe manner. Access to cb_list from callback execution code is synchronized by obtaining new 'cb_lock' rw_semaphore in read mode, which allows executing callbacks in parallel, but excludes any modifications of data from register/unregister code. tcf_block offloads counter type is changed to atomic integer to allow updating the counter concurrently. - Extend classifier ops with new ops->hw_add() and ops->hw_del() callbacks which are used to notify unlocked classifiers when filter is successfully added or deleted to hardware without releasing cb_lock. This is necessary to update classifier state atomically with callback list traversal and updating of all relevant counters and allows unlocked classifiers to synchronize with concurrent reoffload without requiring any changes to driver callback API implementations. New tc flow_action infrastructure is also modified to allow its user to execute without rtnl lock protection. Function tc_setup_flow_action() is modified to conditionally obtain rtnl lock before accessing action state. Action data that is accessed by reference is either copied or reference counted to prevent concurrent action overwrite from deallocating it. New function tc_cleanup_flow_action() is introduced to cleanup/release all such data obtained by tc_setup_flow_action(). Flower classifier (only unlocked classifier at the moment) is modified to use new cls hardware offloads API and no longer obtains rtnl lock before calling it. ==================== Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.