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389 lines
8.1 KiB
389 lines
8.1 KiB
/*
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* Copyright 2014 Jaidev Sridhar.
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* Copyright 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_SWLOCK_H
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#define _CK_SWLOCK_H
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#include <ck_elide.h>
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#include <ck_limits.h>
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#include <ck_pr.h>
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#include <stdbool.h>
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#include <stddef.h>
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struct ck_swlock {
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uint32_t writer;
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uint32_t n_readers;
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};
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typedef struct ck_swlock ck_swlock_t;
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#define CK_SWLOCK_INITIALIZER {0, 0}
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#define CK_SWLOCK_LATCH_BIT (1UL << 31)
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#define CK_SWLOCK_READER_BITS (UINT32_MAX ^ CK_SWLOCK_LATCH_BIT)
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CK_CC_INLINE static void
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ck_swlock_init(struct ck_swlock *rw)
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{
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rw->writer = 0;
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rw->n_readers = 0;
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return;
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}
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CK_CC_INLINE static void
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ck_swlock_write_unlock(ck_swlock_t *rw)
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{
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ck_pr_fence_release();
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ck_pr_store_32(&rw->writer, 0);
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return;
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}
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CK_CC_INLINE static bool
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ck_swlock_locked_writer(ck_swlock_t *rw)
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{
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ck_pr_fence_load();
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return ck_pr_load_32(&rw->writer);
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}
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CK_CC_INLINE static void
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ck_swlock_write_downgrade(ck_swlock_t *rw)
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{
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ck_pr_inc_32(&rw->n_readers);
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ck_swlock_write_unlock(rw);
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return;
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}
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CK_CC_INLINE static bool
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ck_swlock_locked(ck_swlock_t *rw)
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{
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return ck_pr_load_32(&rw->n_readers) | ck_pr_load_32(&rw->writer);
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}
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CK_CC_INLINE static bool
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ck_swlock_write_trylock(ck_swlock_t *rw)
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{
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ck_pr_fas_32(&rw->writer, 1);
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ck_pr_fence_atomic_load();
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if (ck_pr_load_32(&rw->n_readers) != 0) {
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ck_swlock_write_unlock(rw);
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return false;
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}
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return true;
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}
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CK_ELIDE_TRYLOCK_PROTOTYPE(ck_swlock_write, ck_swlock_t,
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ck_swlock_locked, ck_swlock_write_trylock)
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CK_CC_INLINE static void
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ck_swlock_write_lock(ck_swlock_t *rw)
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{
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ck_pr_fas_32(&rw->writer, 1);
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ck_pr_fence_atomic_load();
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while (ck_pr_load_32(&rw->n_readers) != 0)
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ck_pr_stall();
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return;
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}
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CK_CC_INLINE static void
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ck_swlock_write_latch(ck_swlock_t *rw)
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{
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ck_pr_fas_32(&rw->writer, 1);
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ck_pr_fence_atomic_load();
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/* Stall until readers have seen the latch and cleared. */
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while (ck_pr_cas_32(&rw->n_readers, 0, CK_SWLOCK_LATCH_BIT) == false) {
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do {
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ck_pr_stall();
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} while (ck_pr_load_uint(&rw->n_readers) != 0);
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}
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return;
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}
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CK_CC_INLINE static void
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ck_swlock_write_unlatch(ck_swlock_t *rw)
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{
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uint32_t snapshot = ck_pr_load_32(&rw->n_readers);
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uint32_t delta = snapshot & CK_SWLOCK_READER_BITS;
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while (ck_pr_cas_32_value(&rw->n_readers, snapshot, delta, &snapshot) == false) {
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delta = snapshot & CK_SWLOCK_READER_BITS;
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ck_pr_stall();
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}
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ck_swlock_write_unlock(rw);
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return;
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}
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CK_ELIDE_PROTOTYPE(ck_swlock_write, ck_swlock_t,
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ck_swlock_locked, ck_swlock_write_lock,
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ck_swlock_locked_writer, ck_swlock_write_unlock)
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CK_CC_INLINE static bool
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ck_swlock_read_trylock(ck_swlock_t *rw)
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{
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if (ck_pr_load_32(&rw->writer) != 0)
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return false;
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ck_pr_fence_load_atomic();
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if (ck_pr_faa_32(&rw->n_readers, 1) & CK_SWLOCK_LATCH_BIT)
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return false;
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/*
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* Serialize with respect to concurrent write
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* lock operation.
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*/
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ck_pr_fence_atomic_load();
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if (ck_pr_load_32(&rw->writer) == 0) {
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ck_pr_fence_load();
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return true;
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}
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ck_pr_dec_32(&rw->n_readers);
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return false;
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}
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CK_ELIDE_TRYLOCK_PROTOTYPE(ck_swlock_read, ck_swlock_t,
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ck_swlock_locked_writer, ck_swlock_read_trylock)
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CK_CC_INLINE static void
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ck_swlock_read_lock(ck_swlock_t *rw)
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{
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for (;;) {
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while (ck_pr_load_32(&rw->writer) != 0)
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ck_pr_stall();
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ck_pr_inc_32(&rw->n_readers);
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/*
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* Serialize with respect to concurrent write
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* lock operation.
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*/
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ck_pr_fence_atomic_load();
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if (ck_pr_load_32(&rw->writer) == 0)
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break;
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ck_pr_dec_32(&rw->n_readers);
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}
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/* Acquire semantics are necessary. */
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ck_pr_fence_load();
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return;
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}
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CK_CC_INLINE static void
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ck_swlock_read_latchlock(ck_swlock_t *rw)
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{
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for (;;) {
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while (ck_pr_load_32(&rw->writer) != 0)
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ck_pr_stall();
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/* Writer has latched, stall the reader */
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if (ck_pr_faa_32(&rw->n_readers, 1) & CK_SWLOCK_LATCH_BIT) {
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ck_pr_dec_32(&rw->n_readers);
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do {
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ck_pr_stall();
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} while (ck_pr_load_32(&rw->n_readers) & CK_SWLOCK_LATCH_BIT);
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continue;
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}
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/*
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* Serialize with respect to concurrent write
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* lock operation.
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*/
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ck_pr_fence_atomic_load();
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if (ck_pr_load_32(&rw->writer) == 0)
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break;
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ck_pr_dec_32(&rw->n_readers);
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}
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/* Acquire semantics are necessary. */
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ck_pr_fence_load();
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return;
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}
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CK_CC_INLINE static bool
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ck_swlock_locked_reader(ck_swlock_t *rw)
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{
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ck_pr_fence_load();
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return ck_pr_load_32(&rw->n_readers) & CK_SWLOCK_READER_BITS;
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}
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CK_CC_INLINE static void
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ck_swlock_read_unlock(ck_swlock_t *rw)
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{
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ck_pr_fence_release();
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ck_pr_dec_32(&rw->n_readers);
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return;
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}
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CK_ELIDE_PROTOTYPE(ck_swlock_read, ck_swlock_t,
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ck_swlock_locked_writer, ck_swlock_read_lock,
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ck_swlock_locked_reader, ck_swlock_read_unlock)
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/*
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* Recursive writer reader-writer lock implementation.
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*/
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struct ck_swlock_recursive {
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struct ck_swlock rw;
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uint32_t wc;
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};
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typedef struct ck_swlock_recursive ck_swlock_recursive_t;
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#define CK_SWLOCK_RECURSIVE_INITIALIZER {CK_SWLOCK_INITIALIZER, 0}
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CK_CC_INLINE static void
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ck_swlock_recursive_write_lock(ck_swlock_recursive_t *rw)
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{
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ck_pr_fas_32(&rw->rw.writer, 1);
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ck_pr_fence_store_load();
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while (ck_pr_load_32(&rw->rw.n_readers) & CK_SWLOCK_READER_BITS != 0)
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ck_pr_stall();
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rw->wc++;
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return;
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}
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CK_CC_INLINE static void
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ck_swlock_recursive_write_latch(ck_swlock_recursive_t *rw)
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{
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ck_pr_fas_32(&rw->rw.writer, 1);
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ck_pr_fence_store_load();
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while (ck_pr_cas_32(&rw->rw.n_readers, 0, CK_SWLOCK_LATCH_BIT) == false) {
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do {
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ck_pr_stall();
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} while (ck_pr_load_uint(&rw->rw.n_readers) != 0);
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}
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rw->wc++;
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return;
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}
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CK_CC_INLINE static bool
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ck_swlock_recursive_write_trylock(ck_swlock_recursive_t *rw)
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{
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ck_pr_fas_32(&rw->rw.writer, 1);
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ck_pr_fence_store_load();
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if (ck_pr_load_32(&rw->rw.n_readers) & CK_SWLOCK_READER_BITS != 0) {
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ck_pr_store_32(&rw->rw.writer, 0);
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return false;
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}
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rw->wc++;
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return true;
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}
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CK_CC_INLINE static void
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ck_swlock_recursive_write_unlock(ck_swlock_recursive_t *rw)
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{
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if (--rw->wc != 0)
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return;
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ck_pr_fence_release();
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ck_pr_store_32(&rw->rw.writer, 0);
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return;
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}
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CK_CC_INLINE static void
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ck_swlock_recursive_write_unlatch(ck_swlock_recursive_t *rw)
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{
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uint32_t snapshot = ck_pr_load_32(&rw->rw.n_readers);
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uint32_t delta = snapshot & CK_SWLOCK_READER_BITS;
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while (ck_pr_cas_32_value(&rw->rw.n_readers, snapshot, delta, &snapshot) == false) {
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delta = snapshot & CK_SWLOCK_READER_BITS;
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ck_pr_stall();
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}
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ck_swlock_recursive_write_unlock(rw);
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return;
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}
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CK_CC_INLINE static void
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ck_swlock_recursive_read_lock(ck_swlock_recursive_t *rw)
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{
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ck_swlock_read_lock(&rw->rw);
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return;
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}
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CK_CC_INLINE static void
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ck_swlock_recursive_read_latchlock(ck_swlock_recursive_t *rw)
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{
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ck_swlock_read_latchlock(&rw->rw);
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return;
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}
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CK_CC_INLINE static bool
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ck_swlock_recursive_read_trylock(ck_swlock_recursive_t *rw)
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{
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return ck_swlock_read_trylock(&rw->rw);
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}
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CK_CC_INLINE static void
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ck_swlock_recursive_read_unlock(ck_swlock_recursive_t *rw)
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{
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ck_swlock_read_unlock(&rw->rw);
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return;
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}
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#endif /* _CK_SWLOCK_H */
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