You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
126 lines
3.3 KiB
126 lines
3.3 KiB
/*
|
|
* 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 <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_inc_uint(&sq->sequence);
|
|
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_inc_uint(&sq->sequence);
|
|
return;
|
|
}
|
|
|
|
#endif /* _CK_SEQUENCE_H */
|