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2b38a833cd
Explicitly marking domains eligible for RCU synchronization. It's then forbidden to lock these domains in RCU critical section to avoid possible deadlock.
84 lines
2.0 KiB
C
84 lines
2.0 KiB
C
/*
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* BIRD Library -- Read-Copy-Update Basic Operations
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*
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* (c) 2021 Maria Matejka <mq@jmq.cz>
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* (c) 2021 CZ.NIC z.s.p.o.
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*
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* Can be freely distributed and used under the terms of the GNU GPL.
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* Note: all the relevant patents shall be expired.
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*
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* Using the Supplementary Material for User-Level Implementations of Read-Copy-Update
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* by Matthieu Desnoyers, Paul E. McKenney, Alan S. Stern, Michel R. Dagenais and Jonathan Walpole
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* obtained from https://www.efficios.com/pub/rcu/urcu-supp-accepted.pdf
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*/
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#include "lib/rcu.h"
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#include "lib/io-loop.h"
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#include "lib/locking.h"
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_Atomic uint rcu_gp_ctl = RCU_NEST_CNT;
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_Thread_local struct rcu_thread *this_rcu_thread = NULL;
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_Thread_local uint rcu_blocked;
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static list rcu_thread_list;
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static struct rcu_thread main_rcu_thread;
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static DOMAIN(resource) rcu_domain;
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static int
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rcu_gp_ongoing(_Atomic uint *ctl)
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{
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uint val = atomic_load(ctl);
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return (val & RCU_NEST_CNT) && ((val ^ atomic_load_explicit(&rcu_gp_ctl, memory_order_acquire)) & RCU_GP_PHASE);
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}
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static void
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update_counter_and_wait(void)
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{
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atomic_fetch_xor(&rcu_gp_ctl, RCU_GP_PHASE);
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struct rcu_thread *rc;
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WALK_LIST(rc, rcu_thread_list)
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while (rcu_gp_ongoing(&rc->ctl))
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birdloop_yield();
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}
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void
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synchronize_rcu(void)
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{
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if (!rcu_blocked && last_locked)
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bug("Forbidden to synchronize RCU unless an appropriate lock is taken");
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LOCK_DOMAIN(resource, rcu_domain);
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update_counter_and_wait();
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update_counter_and_wait();
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UNLOCK_DOMAIN(resource, rcu_domain);
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}
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void
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rcu_thread_start(struct rcu_thread *rc)
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{
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LOCK_DOMAIN(resource, rcu_domain);
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add_tail(&rcu_thread_list, &rc->n);
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this_rcu_thread = rc;
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UNLOCK_DOMAIN(resource, rcu_domain);
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}
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void
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rcu_thread_stop(struct rcu_thread *rc)
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{
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LOCK_DOMAIN(resource, rcu_domain);
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this_rcu_thread = NULL;
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rem_node(&rc->n);
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UNLOCK_DOMAIN(resource, rcu_domain);
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}
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void
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rcu_init(void)
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{
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rcu_domain = DOMAIN_NEW(resource);
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DOMAIN_SETUP(resource, rcu_domain, "Read-Copy-Update", NULL);
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init_list(&rcu_thread_list);
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rcu_thread_start(&main_rcu_thread);
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}
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