/* * BIRD Library -- Read-Copy-Update Basic Operations * * (c) 2021 Maria Matejka <mq@jmq.cz> * (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. * * Using the Supplementary Material for User-Level Implementations of Read-Copy-Update * by Matthieu Desnoyers, Paul E. McKenney, Alan S. Stern, Michel R. Dagenais and Jonathan Walpole * obtained from https://www.efficios.com/pub/rcu/urcu-supp-accepted.pdf */ #include "lib/rcu.h" #include "lib/io-loop.h" #include "lib/locking.h" _Atomic uint rcu_gp_ctl = RCU_NEST_CNT; _Thread_local struct rcu_thread *this_rcu_thread = NULL; static list rcu_thread_list; static struct rcu_thread main_rcu_thread; DEFINE_DOMAIN(resource); static DOMAIN(resource) rcu_domain; static int rcu_gp_ongoing(_Atomic uint *ctl) { uint val = atomic_load(ctl); return (val & RCU_NEST_CNT) && ((val ^ rcu_gp_ctl) & RCU_GP_PHASE); } static void update_counter_and_wait(void) { atomic_fetch_xor(&rcu_gp_ctl, RCU_GP_PHASE); struct rcu_thread *rc; WALK_LIST(rc, rcu_thread_list) while (rcu_gp_ongoing(&rc->ctl)) birdloop_yield(); } void synchronize_rcu(void) { LOCK_DOMAIN(resource, rcu_domain); update_counter_and_wait(); update_counter_and_wait(); UNLOCK_DOMAIN(resource, rcu_domain); } void rcu_thread_start(struct rcu_thread *rc) { LOCK_DOMAIN(resource, rcu_domain); add_tail(&rcu_thread_list, &rc->n); this_rcu_thread = rc; UNLOCK_DOMAIN(resource, rcu_domain); } void rcu_thread_stop(struct rcu_thread *rc) { LOCK_DOMAIN(resource, rcu_domain); this_rcu_thread = NULL; rem_node(&rc->n); UNLOCK_DOMAIN(resource, rcu_domain); } void rcu_init(void) { rcu_domain = DOMAIN_NEW(resource, "Read-Copy-Update"); init_list(&rcu_thread_list); rcu_thread_start(&main_rcu_thread); }