This increases epoch per-object overhead to 16 bytes.ck_pring
Samy Al Bahra
14 years ago
parent
0f48b6fe7a
commit
10ffb2e6f1
@ -0,0 +1,247 @@
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/*
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* Copyright 2011 Samy Al Bahra.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* The implementation here is inspired from the work described in:
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* Fraser, K. 2004. Practical Lock-Freedom. PhD Thesis, University
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* of Cambridge Computing Laboratory.
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*/
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#include <ck_cc.h>
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#include <ck_epoch.h>
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#include <ck_pr.h>
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#include <ck_stack.h>
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#include <stdbool.h>
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enum {
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CK_EPOCH_USED = 0,
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CK_EPOCH_FREE = 1
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};
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CK_STACK_CONTAINER(struct ck_epoch_record, record_next, ck_epoch_record_container)
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CK_STACK_CONTAINER(struct ck_epoch_entry, stack_entry, ck_epoch_entry_container)
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void
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ck_epoch_init(struct ck_epoch *global, unsigned int threshold)
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{
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ck_stack_init(&global->records);
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global->epoch = 1;
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global->n_free = 0;
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global->threshold = threshold;
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ck_pr_fence_store();
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return;
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}
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struct ck_epoch_record *
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ck_epoch_recycle(struct ck_epoch *global)
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{
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struct ck_epoch_record *record;
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ck_stack_entry_t *cursor;
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unsigned int status;
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if (ck_pr_load_uint(&global->n_free) == 0)
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return (NULL);
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CK_STACK_FOREACH(&global->records, cursor) {
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record = ck_epoch_record_container(cursor);
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if (ck_pr_load_uint(&record->status) == CK_EPOCH_FREE) {
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status = ck_pr_fas_uint(&record->status, CK_EPOCH_USED);
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if (status == CK_EPOCH_FREE) {
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ck_pr_dec_uint(&global->n_free);
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return record;
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}
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}
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}
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return NULL;
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}
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void
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ck_epoch_register(struct ck_epoch *global, struct ck_epoch_record *record)
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{
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size_t i;
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record->status = CK_EPOCH_USED;
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record->active = 0;
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record->epoch = 0;
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record->delta = 0;
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record->n_pending = 0;
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record->n_peak = 0;
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record->n_reclamations = 0;
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record->global = global;
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for (i = 0; i < CK_EPOCH_LENGTH; i++)
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ck_stack_init(&record->pending[i]);
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ck_pr_fence_store();
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ck_stack_push_upmc(&global->records, &record->record_next);
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return;
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}
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void
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ck_epoch_unregister(struct ck_epoch_record *record)
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{
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size_t i;
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record->status = CK_EPOCH_FREE;
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record->active = 0;
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record->epoch = 0;
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record->delta = 0;
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record->n_pending = 0;
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record->n_peak = 0;
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record->n_reclamations = 0;
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for (i = 0; i < CK_EPOCH_LENGTH; i++)
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ck_stack_init(&record->pending[i]);
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ck_pr_inc_uint(&record->global->n_free);
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ck_pr_fence_store();
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return;
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}
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void
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ck_epoch_tick(struct ck_epoch *global, struct ck_epoch_record *record)
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{
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struct ck_epoch_record *c_record;
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ck_stack_entry_t *cursor;
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unsigned int g_epoch = ck_pr_load_uint(&global->epoch);
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g_epoch &= CK_EPOCH_LENGTH - 1;
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CK_STACK_FOREACH(&global->records, cursor) {
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c_record = ck_epoch_record_container(cursor);
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if (ck_pr_load_uint(&c_record->status) == CK_EPOCH_FREE ||
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c_record == record)
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continue;
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if (ck_pr_load_uint(&c_record->active) != 0 &&
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ck_pr_load_uint(&c_record->epoch) != g_epoch)
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return;
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}
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ck_pr_inc_uint(&global->epoch);
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return;
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}
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bool
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ck_epoch_reclaim(struct ck_epoch_record *record)
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{
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struct ck_epoch *global = record->global;
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unsigned int g_epoch = ck_pr_load_uint(&global->epoch);
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unsigned int epoch = record->epoch;
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ck_stack_entry_t *next, *cursor;
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g_epoch &= CK_EPOCH_LENGTH - 1;
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if (epoch == g_epoch)
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return false;
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/*
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* This means all threads with a potential reference to a
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* hazard pointer will have a view as new as or newer than
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* the calling thread. No active reference should exist to
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* any object in the record's pending list.
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*/
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CK_STACK_FOREACH_SAFE(&record->pending[g_epoch], cursor, next) {
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struct ck_epoch_entry *entry = ck_epoch_entry_container(cursor);
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entry->destroy(entry);
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record->n_pending--;
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record->n_reclamations++;
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}
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ck_stack_init(&record->pending[g_epoch]);
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record->epoch = g_epoch;
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record->delta = 0;
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return true;
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}
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void
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ck_epoch_write_begin(struct ck_epoch_record *record)
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{
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struct ck_epoch *global = record->global;
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ck_pr_store_uint(&record->active, record->active + 1);
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ck_pr_fence_store();
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/*
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* In the case of recursive write sections, avoid ticking
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* over global epoch.
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*/
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if (record->active > 1)
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return;
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for (;;) {
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if (ck_epoch_reclaim(record) == true)
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break;
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if (++record->delta >= global->threshold) {
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record->delta = 0;
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ck_epoch_tick(global, record);
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continue;
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}
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break;
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}
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return;
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}
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void
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ck_epoch_free(struct ck_epoch_record *record,
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ck_epoch_destructor_t destroy,
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ck_epoch_entry_t *entry)
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{
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unsigned int epoch = ck_pr_load_uint(&record->epoch);
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struct ck_epoch *global = record->global;
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entry->destroy = destroy;
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ck_stack_push_spnc(&record->pending[epoch], &entry->stack_entry);
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record->n_pending += 1;
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if (record->n_pending > record->n_peak)
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record->n_peak = record->n_pending;
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if (record->n_pending >= global->threshold && ck_epoch_reclaim(record) == false)
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ck_epoch_tick(global, record);
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return;
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}
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void
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ck_epoch_purge(struct ck_epoch_record *record)
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{
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ck_backoff_t backoff = CK_BACKOFF_INITIALIZER;
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while (record->n_pending > 0) {
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ck_epoch_reclaim(record);
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ck_epoch_tick(record->global, record);
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if (record->n_pending > 0)
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ck_backoff_gb(&backoff);
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}
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return;
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}
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