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Diffstat (limited to 'include/spinlock/clh.h')
| -rw-r--r-- | include/spinlock/clh.h | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/include/spinlock/clh.h b/include/spinlock/clh.h new file mode 100644 index 0000000..1133806 --- /dev/null +++ b/include/spinlock/clh.h @@ -0,0 +1,122 @@ +/* + * 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_CLH_H +#define CK_SPINLOCK_CLH_H + +#include <ck_cc.h> +#include <ck_limits.h> +#include <ck_pr.h> +#include <ck_stdbool.h> +#include <ck_stddef.h> + +#ifndef CK_F_SPINLOCK_CLH +#define CK_F_SPINLOCK_CLH + +struct ck_spinlock_clh { + unsigned int wait; + struct ck_spinlock_clh *previous; +}; +typedef struct ck_spinlock_clh ck_spinlock_clh_t; + +CK_CC_INLINE static void +ck_spinlock_clh_init(struct ck_spinlock_clh **lock, struct ck_spinlock_clh *unowned) +{ + + unowned->previous = NULL; + unowned->wait = false; + *lock = unowned; + ck_pr_barrier(); + return; +} + +CK_CC_INLINE static bool +ck_spinlock_clh_locked(struct ck_spinlock_clh **queue) +{ + struct ck_spinlock_clh *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_clh_lock(struct ck_spinlock_clh **queue, struct ck_spinlock_clh *thread) +{ + struct ck_spinlock_clh *previous; + + /* Indicate to the next thread on queue that they will have to block. */ + thread->wait = true; + ck_pr_fence_store_atomic(); + + /* + * Mark current request as last request. Save reference to previous + * request. + */ + previous = ck_pr_fas_ptr(queue, thread); + thread->previous = previous; + + /* Wait until previous thread is done with lock. */ + ck_pr_fence_load(); + while (ck_pr_load_uint(&previous->wait) == true) + ck_pr_stall(); + + ck_pr_fence_lock(); + return; +} + +CK_CC_INLINE static void +ck_spinlock_clh_unlock(struct ck_spinlock_clh **thread) +{ + struct ck_spinlock_clh *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_CLH */ +#endif /* CK_SPINLOCK_CLH_H */ |