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Diffstat (limited to 'include/spinlock/hclh.h')
| -rw-r--r-- | include/spinlock/hclh.h | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/include/spinlock/hclh.h b/include/spinlock/hclh.h new file mode 100644 index 0000000..296448b --- /dev/null +++ b/include/spinlock/hclh.h @@ -0,0 +1,145 @@ +/* + * 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 */ |