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272 lines
6.4 KiB
272 lines
6.4 KiB
/*
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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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#ifndef _CK_EPOCH_H
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#define _CK_EPOCH_H
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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_pr.h>
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#include <ck_stack.h>
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#include <stdbool.h>
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/*
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* CK_EPOCH_LENGTH must be a power of 2.
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*/
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#ifndef CK_EPOCH_LENGTH
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#define CK_EPOCH_LENGTH 4
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#endif
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typedef void (*ck_epoch_destructor_t)(ck_stack_entry_t *);
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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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struct ck_epoch;
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struct ck_epoch_record {
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unsigned int active;
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unsigned int status;
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unsigned int epoch;
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ck_stack_t pending[CK_EPOCH_LENGTH];
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unsigned int delta;
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struct ck_epoch *global;
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ck_stack_entry_t record_next;
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} CK_CC_CACHELINE;
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typedef struct ck_epoch_record ck_epoch_record_t;
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struct ck_epoch {
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unsigned int epoch;
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char pad[CK_MD_CACHELINE - sizeof(unsigned int)];
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ck_stack_t records;
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unsigned int threshold;
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unsigned int n_free;
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ck_epoch_destructor_t destroy;
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};
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typedef struct ck_epoch ck_epoch_t;
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CK_STACK_CONTAINER(struct ck_epoch_record, record_next, ck_epoch_record_container)
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CK_CC_INLINE static void
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ck_epoch_init(struct ck_epoch *global,
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unsigned int threshold,
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ck_epoch_destructor_t destroy)
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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->destroy = destroy;
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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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CK_CC_INLINE static 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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CK_CC_INLINE static 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->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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CK_CC_INLINE static void
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ck_epoch_unregister(struct ck_epoch_record *record)
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{
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record->status = CK_EPOCH_FREE;
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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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CK_CC_INLINE static void
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ck_epoch_update(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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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) == true &&
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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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CK_CC_INLINE static void
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ck_epoch_activate(struct ck_epoch_record *record)
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{
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ck_pr_store_uint(&record->active, 1);
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ck_pr_fence_store();
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return;
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}
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CK_CC_INLINE static void
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ck_epoch_deactivate(struct ck_epoch_record *record)
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{
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ck_pr_fence_store();
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ck_pr_store_uint(&record->active, 0);
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return;
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}
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CK_CC_INLINE static void
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ck_epoch_start(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;
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for (;;) {
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g_epoch = ck_pr_load_uint(&global->epoch);
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if (record->epoch != g_epoch) {
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ck_stack_entry_t *next, *cursor;
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unsigned int epoch = record->epoch & (CK_EPOCH_LENGTH - 1);
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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[epoch], cursor, next)
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global->destroy(cursor);
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ck_stack_init(&record->pending[epoch]);
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ck_pr_store_uint(&record->epoch, g_epoch);
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record->delta = 0;
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break;
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}
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if (++record->delta >= global->threshold) {
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record->delta = 0;
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ck_epoch_update(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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CK_CC_INLINE static void
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ck_epoch_stop(struct ck_epoch_record *record CK_CC_UNUSED)
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{
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return;
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}
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CK_CC_INLINE static void
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ck_epoch_begin(struct ck_epoch_record *record)
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{
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ck_epoch_activate(record);
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ck_epoch_start(record);
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return;
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}
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CK_CC_INLINE static void
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ck_epoch_end(struct ck_epoch_record *record)
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{
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ck_epoch_deactivate(record);
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return;
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}
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CK_CC_INLINE static void
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ck_epoch_flush(struct ck_epoch_record *record)
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{
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ck_epoch_update(record->global, record);
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ck_epoch_start(record);
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return;
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}
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CK_CC_INLINE static void
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ck_epoch_free(struct ck_epoch_record *record, ck_stack_entry_t *entry)
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{
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unsigned int epoch = ck_pr_load_uint(&record->epoch) & (CK_EPOCH_LENGTH - 1);
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ck_stack_push_spnc(&record->pending[epoch], entry);
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record->delta++;
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return;
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}
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#endif /* _CK_EPOCH_H */
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