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.
170 lines
4.4 KiB
170 lines
4.4 KiB
/*
|
|
* Copyright 2011 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_BRLOCK_H
|
|
#define _CK_BRLOCK_H
|
|
|
|
/*
|
|
* Big reader spinlocks provide cache-local contention-free read
|
|
* lock acquisition in the absence of writers. This comes at the
|
|
* cost of O(n) write lock acquisition. They were first implemented
|
|
* in the Linux kernel by Ingo Molnar and David S. Miller around the
|
|
* year 2000.
|
|
*
|
|
* This implementation is thread-agnostic which comes at the cost
|
|
* of larger reader objects due to necessary linkage overhead. In
|
|
* order to cut down on TLB pressure, it is recommended to allocate
|
|
* these objects on the same page.
|
|
*/
|
|
|
|
#include <ck_pr.h>
|
|
#include <stdbool.h>
|
|
#include <stddef.h>
|
|
|
|
struct ck_brlock_reader {
|
|
unsigned int n_readers;
|
|
struct ck_brlock_reader *previous;
|
|
struct ck_brlock_reader *next;
|
|
};
|
|
typedef struct ck_brlock_reader ck_brlock_reader_t;
|
|
|
|
#define CK_BRLOCK_READER_INITIALIZER {0}
|
|
|
|
struct ck_brlock {
|
|
struct ck_brlock_reader *readers;
|
|
unsigned int writer;
|
|
};
|
|
typedef struct ck_brlock ck_brlock_t;
|
|
|
|
#define CK_BRLOCK_INITIALIZER {NULL, false}
|
|
|
|
CK_CC_INLINE static void
|
|
ck_brlock_init(struct ck_brlock *br)
|
|
{
|
|
|
|
br->readers = NULL;
|
|
br->writer = false;
|
|
ck_pr_fence_memory();
|
|
return;
|
|
}
|
|
|
|
CK_CC_INLINE static void
|
|
ck_brlock_write_lock(struct ck_brlock *br)
|
|
{
|
|
struct ck_brlock_reader *cursor;
|
|
|
|
/*
|
|
* As the frequency of write acquisitions should be low,
|
|
* there is no point to more advanced contention avoidance.
|
|
*/
|
|
while (ck_pr_fas_uint(&br->writer, true) == true)
|
|
ck_pr_stall();
|
|
|
|
/* The reader list is protected under the writer br. */
|
|
for (cursor = br->readers; cursor != NULL; cursor = cursor->next) {
|
|
while (ck_pr_load_uint(&cursor->n_readers) != 0)
|
|
ck_pr_stall();
|
|
}
|
|
|
|
/* This branch should never be reached. */
|
|
return;
|
|
}
|
|
|
|
CK_CC_INLINE static void
|
|
ck_brlock_write_unlock(struct ck_brlock *br)
|
|
{
|
|
|
|
ck_pr_fence_memory();
|
|
ck_pr_store_uint(&br->writer, false);
|
|
return;
|
|
}
|
|
|
|
CK_CC_INLINE static void
|
|
ck_brlock_read_register(struct ck_brlock *br, struct ck_brlock_reader *reader)
|
|
{
|
|
|
|
reader->n_readers = 0;
|
|
reader->previous = NULL;
|
|
|
|
/* Implicit compiler barrier. */
|
|
ck_brlock_write_lock(br);
|
|
|
|
reader->next = ck_pr_load_ptr(&br->readers);
|
|
if (reader->next != NULL)
|
|
reader->next->previous = reader;
|
|
ck_pr_store_ptr(&br->readers, reader);
|
|
|
|
ck_brlock_write_unlock(br);
|
|
return;
|
|
}
|
|
|
|
CK_CC_INLINE static void
|
|
ck_brlock_read_unregister(struct ck_brlock *br, struct ck_brlock_reader *reader)
|
|
{
|
|
|
|
ck_brlock_write_lock(br);
|
|
|
|
if (reader->next != NULL)
|
|
reader->next->previous = reader->previous;
|
|
|
|
if (reader->previous != NULL)
|
|
reader->previous->next = reader->next;
|
|
else
|
|
br->readers = reader->next;
|
|
|
|
ck_brlock_write_unlock(br);
|
|
return;
|
|
}
|
|
|
|
CK_CC_INLINE static void
|
|
ck_brlock_read_lock(struct ck_brlock *br, struct ck_brlock_reader *reader)
|
|
{
|
|
|
|
for (;;) {
|
|
while (ck_pr_load_uint(&br->writer) == true)
|
|
ck_pr_stall();
|
|
|
|
ck_pr_inc_uint(&reader->n_readers);
|
|
|
|
if (ck_pr_load_uint(&br->writer) == false)
|
|
break;
|
|
|
|
ck_pr_dec_uint(&reader->n_readers);
|
|
}
|
|
|
|
return;
|
|
}
|
|
|
|
CK_CC_INLINE static void
|
|
ck_brlock_read_unlock(struct ck_brlock_reader *reader)
|
|
{
|
|
|
|
ck_pr_dec_uint(&reader->n_readers);
|
|
return;
|
|
}
|
|
|
|
#endif /* _CK_BRLOCK_H */
|