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123 lines
3.6 KiB
123 lines
3.6 KiB
/*
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* Copyright 2010-2015 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_SPINLOCK_CLH_H
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#define CK_SPINLOCK_CLH_H
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#include <ck_cc.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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#ifndef CK_F_SPINLOCK_CLH
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#define CK_F_SPINLOCK_CLH
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struct ck_spinlock_clh {
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unsigned int wait;
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struct ck_spinlock_clh *previous;
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};
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typedef struct ck_spinlock_clh ck_spinlock_clh_t;
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CK_CC_INLINE static void
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ck_spinlock_clh_init(struct ck_spinlock_clh **lock, struct ck_spinlock_clh *unowned)
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{
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unowned->previous = NULL;
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unowned->wait = false;
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*lock = unowned;
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ck_pr_barrier();
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return;
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}
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CK_CC_INLINE static bool
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ck_spinlock_clh_locked(struct ck_spinlock_clh **queue)
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{
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struct ck_spinlock_clh *head;
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bool r;
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head = ck_pr_load_ptr(queue);
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r = ck_pr_load_uint(&head->wait);
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ck_pr_fence_acquire();
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return r;
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}
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CK_CC_INLINE static void
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ck_spinlock_clh_lock(struct ck_spinlock_clh **queue, struct ck_spinlock_clh *thread)
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{
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struct ck_spinlock_clh *previous;
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/* Indicate to the next thread on queue that they will have to block. */
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thread->wait = true;
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ck_pr_fence_store_atomic();
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/*
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* Mark current request as last request. Save reference to previous
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* request.
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*/
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previous = ck_pr_fas_ptr(queue, thread);
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thread->previous = previous;
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/* Wait until previous thread is done with lock. */
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ck_pr_fence_load();
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while (ck_pr_load_uint(&previous->wait) == true)
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ck_pr_stall();
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ck_pr_fence_lock();
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return;
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}
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CK_CC_INLINE static void
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ck_spinlock_clh_unlock(struct ck_spinlock_clh **thread)
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{
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struct ck_spinlock_clh *previous;
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/*
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* If there are waiters, they are spinning on the current node wait
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* flag. The flag is cleared so that the successor may complete an
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* acquisition. If the caller is pre-empted then the predecessor field
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* may be updated by a successor's lock operation. In order to avoid
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* this, save a copy of the predecessor before setting the flag.
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*/
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previous = thread[0]->previous;
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/*
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* We have to pay this cost anyways, use it as a compiler barrier too.
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*/
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ck_pr_fence_unlock();
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ck_pr_store_uint(&(*thread)->wait, false);
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/*
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* Predecessor is guaranteed not to be spinning on previous request,
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* so update caller to use previous structure. This allows successor
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* all the time in the world to successfully read updated wait flag.
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*/
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*thread = previous;
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return;
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}
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#endif /* CK_F_SPINLOCK_CLH */
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#endif /* CK_SPINLOCK_CLH_H */
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