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/*
* Copyright 2013-2015 Olivier Houchard
* 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_SPINLOCK_HCLH_H
#define CK_SPINLOCK_HCLH_H
#include <ck_cc.h>
#include <ck_pr.h>
#include <ck_stdbool.h>
#include <ck_stddef.h>
#ifndef CK_F_SPINLOCK_HCLH
#define CK_F_SPINLOCK_HCLH
struct ck_spinlock_hclh {
unsigned int wait;
unsigned int splice;
int cluster_id;
struct ck_spinlock_hclh *previous;
};
typedef struct ck_spinlock_hclh ck_spinlock_hclh_t;
CK_CC_INLINE static void
ck_spinlock_hclh_init(struct ck_spinlock_hclh **lock,
struct ck_spinlock_hclh *unowned,
int cluster_id)
{
unowned->previous = NULL;
unowned->wait = false;
unowned->splice = false;
unowned->cluster_id = cluster_id;
*lock = unowned;
ck_pr_barrier();
return;
}
CK_CC_INLINE static bool
ck_spinlock_hclh_locked(struct ck_spinlock_hclh **queue)
{
struct ck_spinlock_hclh *head;
bool r;
head = ck_pr_load_ptr(queue);
r = ck_pr_load_uint(&head->wait);
ck_pr_fence_acquire();
return r;
}
CK_CC_INLINE static void
ck_spinlock_hclh_lock(struct ck_spinlock_hclh **glob_queue,
struct ck_spinlock_hclh **local_queue,
struct ck_spinlock_hclh *thread)
{
struct ck_spinlock_hclh *previous, *local_tail;
/* Indicate to the next thread on queue that they will have to block. */
thread->wait = true;
thread->splice = false;
thread->cluster_id = (*local_queue)->cluster_id;
/* Serialize with respect to update of local queue. */
ck_pr_fence_store_atomic();
/* Mark current request as last request. Save reference to previous request. */
previous = ck_pr_fas_ptr(local_queue, thread);
thread->previous = previous;
/* Wait until previous thread from the local queue is done with lock. */
ck_pr_fence_load();
if (previous->previous != NULL &&
previous->cluster_id == thread->cluster_id) {
while (ck_pr_load_uint(&previous->wait) == true)
ck_pr_stall();
/* We're head of the global queue, we're done */
if (ck_pr_load_uint(&previous->splice) == false)
return;
}
/* Now we need to splice the local queue into the global queue. */
local_tail = ck_pr_load_ptr(local_queue);
previous = ck_pr_fas_ptr(glob_queue, local_tail);
ck_pr_store_uint(&local_tail->splice, true);
/* Wait until previous thread from the global queue is done with lock. */
while (ck_pr_load_uint(&previous->wait) == true)
ck_pr_stall();
ck_pr_fence_lock();
return;
}
CK_CC_INLINE static void
ck_spinlock_hclh_unlock(struct ck_spinlock_hclh **thread)
{
struct ck_spinlock_hclh *previous;
/*
* If there are waiters, they are spinning on the current node wait
* flag. The flag is cleared so that the successor may complete an
* acquisition. If the caller is pre-empted then the predecessor field
* may be updated by a successor's lock operation. In order to avoid
* this, save a copy of the predecessor before setting the flag.
*/
previous = thread[0]->previous;
/* We have to pay this cost anyways, use it as a compiler barrier too. */
ck_pr_fence_unlock();
ck_pr_store_uint(&(*thread)->wait, false);
/*
* Predecessor is guaranteed not to be spinning on previous request,
* so update caller to use previous structure. This allows successor
* all the time in the world to successfully read updated wait flag.
*/
*thread = previous;
return;
}
#endif /* CK_F_SPINLOCK_HCLH */
#endif /* CK_SPINLOCK_HCLH_H */
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