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76 lines
1.7 KiB
C
76 lines
1.7 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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#ifndef _BIRD_RCU_H_
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#define _BIRD_RCU_H_
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#include "lib/birdlib.h"
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#include "lib/lists.h"
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#include <stdatomic.h>
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#define RCU_GP_PHASE 0x100
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#define RCU_NEST_MASK (RCU_GP_PHASE-1)
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#define RCU_NEST_CNT 1
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extern _Atomic u64 rcu_global_phase;
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struct rcu_thread {
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struct rcu_thread * _Atomic next;
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_Atomic u64 ctl;
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};
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extern _Thread_local struct rcu_thread this_rcu_thread;
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extern _Thread_local uint rcu_blocked;
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static inline void rcu_read_lock(void)
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{
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/* Increment the nesting counter */
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u64 before = atomic_fetch_add_explicit(
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&this_rcu_thread.ctl,
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RCU_NEST_CNT,
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memory_order_acq_rel
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);
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if (before & RCU_NEST_MASK)
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return;
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/* Update the phase */
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u64 phase = atomic_load_explicit(&rcu_global_phase, memory_order_acquire);
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u64 dif = (before & ~RCU_NEST_MASK) ^ phase;
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if (dif)
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atomic_fetch_xor_explicit(
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&this_rcu_thread.ctl,
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dif,
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memory_order_acq_rel);
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}
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static inline void rcu_read_unlock(void)
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{
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/* Just decrement the nesting counter; when unlocked, nobody cares */
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atomic_fetch_sub(&this_rcu_thread.ctl, RCU_NEST_CNT);
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}
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static inline _Bool rcu_read_active(void)
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{
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return !!(atomic_load_explicit(&this_rcu_thread.ctl, memory_order_acquire) & RCU_NEST_MASK);
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}
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void synchronize_rcu(void);
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/* Registering and unregistering a birdloop. To be called from birdloop implementation */
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void rcu_thread_start(void);
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void rcu_thread_stop(void);
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/* Run this from resource init */
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void rcu_init(void);
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#endif
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