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Diffstat (limited to '')
-rw-r--r-- | include/ck_sequence.h | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/include/ck_sequence.h b/include/ck_sequence.h new file mode 100644 index 0000000..6a482b9 --- /dev/null +++ b/include/ck_sequence.h @@ -0,0 +1,125 @@ +/* + * Copyright 2010-2015 Samy Al Bahra. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#ifndef CK_SEQUENCE_H +#define CK_SEQUENCE_H + +#include <ck_cc.h> +#include <ck_pr.h> +#include <ck_stdbool.h> + +struct ck_sequence { + unsigned int sequence; +}; +typedef struct ck_sequence ck_sequence_t; + +#define CK_SEQUENCE_INITIALIZER { .sequence = 0 } + +CK_CC_INLINE static void +ck_sequence_init(struct ck_sequence *sq) +{ + + ck_pr_store_uint(&sq->sequence, 0); + return; +} + +CK_CC_INLINE static unsigned int +ck_sequence_read_begin(const struct ck_sequence *sq) +{ + unsigned int version; + + for (;;) { + version = ck_pr_load_uint(&sq->sequence); + + /* + * If a sequence is even then associated data may be in a + * consistent state. + */ + if (CK_CC_LIKELY((version & 1) == 0)) + break; + + /* + * If a sequence is odd then a thread is in the middle of an + * update. Retry the read to avoid operating on inconsistent + * data. + */ + ck_pr_stall(); + } + + ck_pr_fence_load(); + return version; +} + +CK_CC_INLINE static bool +ck_sequence_read_retry(const struct ck_sequence *sq, unsigned int version) +{ + + /* + * If the sequence number was updated then a read should be + * re-attempted. + */ + ck_pr_fence_load(); + return ck_pr_load_uint(&sq->sequence) != version; +} + +#define CK_SEQUENCE_READ(seqlock, version) \ + for (*(version) = 1; \ + (*(version) != 0) && (*(version) = ck_sequence_read_begin(seqlock), 1); \ + *(version) = ck_sequence_read_retry(seqlock, *(version))) + +/* + * This must be called after a successful mutex acquisition. + */ +CK_CC_INLINE static void +ck_sequence_write_begin(struct ck_sequence *sq) +{ + + /* + * Increment the sequence to an odd number to indicate + * the beginning of a write update. + */ + ck_pr_store_uint(&sq->sequence, sq->sequence + 1); + ck_pr_fence_store(); + return; +} + +/* + * This must be called before mutex ownership is relinquished. + */ +CK_CC_INLINE static void +ck_sequence_write_end(struct ck_sequence *sq) +{ + + /* + * Increment the sequence to an even number to indicate + * completion of a write update. + */ + ck_pr_fence_store(); + ck_pr_store_uint(&sq->sequence, sq->sequence + 1); + return; +} + +#endif /* CK_SEQUENCE_H */ |