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/*
* 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_birdloop *this_rcu_birdloop = NULL;
static list rcu_birdloop_list;
static struct rcu_birdloop main_rcu_birdloop;
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_birdloop *rc;
WALK_LIST(rc, rcu_birdloop_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_birdloop_start(struct rcu_birdloop *rc)
{
LOCK_DOMAIN(resource, rcu_domain);
add_tail(&rcu_birdloop_list, &rc->n);
this_rcu_birdloop = rc;
UNLOCK_DOMAIN(resource, rcu_domain);
}
void
rcu_birdloop_stop(struct rcu_birdloop *rc)
{
LOCK_DOMAIN(resource, rcu_domain);
this_rcu_birdloop = 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_birdloop_list);
rcu_birdloop_start(&main_rcu_birdloop);
}
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