From 058ed711397df75350d905fc135758a6470c0143 Mon Sep 17 00:00:00 2001 From: Maria Matejka Date: Fri, 12 Nov 2021 22:58:40 +0100 Subject: Introducing basic RCU primitives for lock-less shared data structures --- lib/rcu.h | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100644 lib/rcu.h (limited to 'lib/rcu.h') diff --git a/lib/rcu.h b/lib/rcu.h new file mode 100644 index 00000000..c537a1ef --- /dev/null +++ b/lib/rcu.h @@ -0,0 +1,55 @@ +/* + * BIRD Library -- Read-Copy-Update Basic Operations + * + * (c) 2021 Maria Matejka + * (c) 2021 CZ.NIC z.s.p.o. + * + * Can be freely distributed and used under the terms of the GNU GPL. + * Note: all the relevant patents shall be expired. + */ + +#ifndef _BIRD_RCU_H_ +#define _BIRD_RCU_H_ + +#include "lib/birdlib.h" +#include "lib/lists.h" +#include + +#define RCU_GP_PHASE 0x100000 +#define RCU_NEST_MASK 0x0fffff +#define RCU_NEST_CNT 0x000001 + +extern _Atomic uint rcu_gp_ctl; + +struct rcu_birdloop { + node n; + _Atomic uint ctl; +}; + +extern _Thread_local struct rcu_birdloop *this_rcu_birdloop; + +static inline void rcu_read_lock(void) +{ + uint cmp = atomic_load_explicit(&this_rcu_birdloop->ctl, memory_order_acquire); + + if (cmp & RCU_NEST_MASK) + atomic_store_explicit(&this_rcu_birdloop->ctl, cmp + RCU_NEST_CNT, memory_order_relaxed); + else + atomic_store(&this_rcu_birdloop->ctl, atomic_load_explicit(&rcu_gp_ctl, memory_order_acquire)); +} + +static inline void rcu_read_unlock(void) +{ + atomic_fetch_sub(&this_rcu_birdloop->ctl, RCU_NEST_CNT); +} + +void synchronize_rcu(void); + +/* Registering and unregistering a birdloop. To be called from birdloop implementation */ +void rcu_birdloop_start(struct rcu_birdloop *); +void rcu_birdloop_stop(struct rcu_birdloop *); + +/* Run this from resource init */ +void rcu_init(void); + +#endif -- cgit v1.2.3