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127 lines
3.3 KiB
127 lines
3.3 KiB
/*
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* Copyright 2010-2014 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_SEQUENCE_H
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#define _CK_SEQUENCE_H
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#include <ck_cc.h>
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#include <ck_pr.h>
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#include <stdbool.h>
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struct ck_sequence {
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unsigned int sequence;
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};
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typedef struct ck_sequence ck_sequence_t;
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#define CK_SEQUENCE_INITIALIZER { .sequence = 0 }
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CK_CC_INLINE static void
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ck_sequence_init(struct ck_sequence *sq)
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{
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ck_pr_store_uint(&sq->sequence, 0);
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return;
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}
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CK_CC_INLINE static unsigned int
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ck_sequence_read_begin(struct ck_sequence *sq)
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{
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unsigned int version;
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for (;;) {
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version = ck_pr_load_uint(&sq->sequence);
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/*
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* If a sequence is even then associated data may be in a
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* consistent state.
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*/
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if ((version & 1) == 0)
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break;
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/*
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* If a sequence is odd then a thread is in the middle of an
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* update. Retry the read to avoid operating on inconsistent
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* data.
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*/
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ck_pr_stall();
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}
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ck_pr_fence_load();
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return version;
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}
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CK_CC_INLINE static bool
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ck_sequence_read_retry(struct ck_sequence *sq, unsigned int version)
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{
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/*
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* If the sequence number was updated then a read should be
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* re-attempted.
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*/
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ck_pr_fence_load();
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return ck_pr_load_uint(&sq->sequence) != version;
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}
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#define CK_SEQUENCE_READ(seqlock, version) \
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for (*(version) = 1; \
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(*(version) != 0) && (*(version) = ck_sequence_read_begin(seqlock), 1); \
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*(version) = ck_sequence_read_retry(seqlock, *(version)))
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/*
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* This must be called after a successful mutex acquisition.
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*/
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CK_CC_INLINE static void
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ck_sequence_write_begin(struct ck_sequence *sq)
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{
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/*
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* Increment the sequence to an odd number to indicate
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* the beginning of a write update.
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*/
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ck_pr_inc_uint(&sq->sequence);
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ck_pr_fence_store();
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return;
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}
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/*
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* This must be called before mutex ownership is relinquished.
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*/
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CK_CC_INLINE static void
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ck_sequence_write_end(struct ck_sequence *sq)
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{
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/*
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* Increment the sequence to an even number to indicate
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* completion of a write update.
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*/
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ck_pr_fence_store();
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ck_pr_inc_uint(&sq->sequence);
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return;
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}
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#endif /* _CK_SEQUENCE_H */
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