Currently, all netlink protocol handlers for updating rules, actions and qdiscs are protected with single global rtnl lock which removes any possibility for parallelism. This patch set is a third step to remove rtnl lock dependency from TC rules update path.
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. The goal of this change is to refactor flower classifier to support unlocked execution and register it with unlocked flag. This patch set implements following changes to make flower classifier concurrency-safe: - Implement reference counting for individual filters. Change fl_get to take reference to filter. Implement tp->ops->put callback that was introduced in cls API patch set to release reference to flower filter. - Use tp->lock spinlock to protect internal classifier data structures from concurrent modification. - Handle concurrent tcf proto deletion by returning EAGAIN, which will cause cls API to retry and create new proto instance or return error to the user (depending on message type). - Handle concurrent insertion of filter with same priority and handle by returning EAGAIN, which will cause cls API to lookup filter again and process it accordingly to netlink message flags. - Extend flower mask with reference counting and protect masks list with masks_lock spinlock. - Prevent concurrent mask insertion by inserting temporary value to masks hash table. This is necessary because mask initialization is a sleeping operation and cannot be done while holding tp->lock. Tcf hw offloads API is not changed by this patch set and still requires caller to hold rtnl lock. Refactored flower classifier tracks rtnl lock state by means of 'rtnl_held' flag provided by cls API and obtains the lock before calling hw offloads. With these changes flower classifier is safely registered with TCF_PROTO_OPS_DOIT_UNLOCKED flag in last patch. Github: [https://github.com/vbuslov/linux/tree/unlocked_flower_cong_1] Vlad Buslov (12): net: sched: flower: don't check for rtnl on head dereference net: sched: flower: refactor fl_change net: sched: flower: introduce reference counting for filters net: sched: flower: track filter deletion with flag net: sched: flower: add reference counter to flower mask net: sched: flower: handle concurrent mask insertion net: sched: flower: protect masks list with spinlock net: sched: flower: handle concurrent filter insertion in fl_change net: sched: flower: handle concurrent tcf proto deletion net: sched: flower: protect flower classifier state with spinlock net: sched: flower: track rtnl lock state net: sched: flower: set unlocked flag for flower proto ops net/sched/cls_flower.c | 424 +++++++++++++++++++++++++++++++++++++------------ 1 file changed, 321 insertions(+), 103 deletions(-) -- 2.13.6
