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156 lines
4.5 KiB
156 lines
4.5 KiB
/*
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* Copyright 2011-2012 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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#ifndef CK_EPOCH_LENGTH
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#define CK_EPOCH_LENGTH 4
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#endif
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struct ck_epoch_entry;
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typedef struct ck_epoch_entry ck_epoch_entry_t;
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typedef void ck_epoch_cb_t(ck_epoch_entry_t *);
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/*
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* This should be embedded into objects you wish to be the target of
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* ck_epoch_cb_t functions (with ck_epoch_call).
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*/
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struct ck_epoch_entry {
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ck_epoch_cb_t *function;
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ck_stack_entry_t stack_entry;
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};
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/*
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* Return pointer to ck_epoch_entry container object.
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*/
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#define CK_EPOCH_CONTAINER(T, M, N) CK_CC_CONTAINER(struct ck_epoch_entry, T, M, N)
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struct ck_epoch_record {
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unsigned int state;
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unsigned int epoch;
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unsigned int active;
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unsigned int n_pending;
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unsigned int n_peak;
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unsigned long n_dispatch;
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ck_stack_t pending[CK_EPOCH_LENGTH];
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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 n_free;
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};
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typedef struct ck_epoch ck_epoch_t;
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/*
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* Marks the beginning of an epoch-protected section.
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*/
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CK_CC_INLINE static void
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ck_epoch_begin(ck_epoch_t *epoch, ck_epoch_record_t *record)
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{
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/*
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* Only observe new epoch if thread is not recursing into a read
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* section.
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*/
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if (record->active == 0) {
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unsigned int g_epoch = ck_pr_load_uint(&epoch->epoch);
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/*
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* It is possible for loads to be re-ordered before the store
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* is committed into the caller's epoch and active fields.
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* Execute a full barrier to serialize stores with respect to
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* loads
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*/
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ck_pr_store_uint(&record->epoch, g_epoch);
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ck_pr_store_uint(&record->active, 1);
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ck_pr_fence_strict_memory();
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return;
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}
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ck_pr_store_uint(&record->active, record->active + 1);
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return;
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}
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/*
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* Marks the end of an epoch-protected section.
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*/
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CK_CC_INLINE static void
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ck_epoch_end(ck_epoch_t *global, ck_epoch_record_t *record)
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{
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(void)global;
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ck_pr_fence_memory();
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ck_pr_store_uint(&record->active, record->active - 1);
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return;
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}
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/*
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* Defers the execution of the function pointed to by the "cb"
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* argument until an epoch counter loop. This allows for a
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* non-blocking deferral.
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*/
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CK_CC_INLINE static void
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ck_epoch_call(ck_epoch_t *epoch,
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ck_epoch_record_t *record,
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ck_epoch_entry_t *entry,
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ck_epoch_cb_t *function)
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{
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unsigned int e = ck_pr_load_uint(&epoch->epoch);
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unsigned int offset = e & (CK_EPOCH_LENGTH - 1);
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record->n_pending++;
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entry->function = function;
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ck_stack_push_spnc(&record->pending[offset], &entry->stack_entry);
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return;
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}
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void ck_epoch_init(ck_epoch_t *);
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ck_epoch_record_t *ck_epoch_recycle(ck_epoch_t *);
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void ck_epoch_register(ck_epoch_t *, ck_epoch_record_t *);
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void ck_epoch_unregister(ck_epoch_t *, ck_epoch_record_t *);
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bool ck_epoch_poll(ck_epoch_t *, ck_epoch_record_t *);
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void ck_epoch_synchronize(ck_epoch_t *, ck_epoch_record_t *);
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void ck_epoch_barrier(ck_epoch_t *, ck_epoch_record_t *);
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#endif /* _CK_EPOCH_H */
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