| /* |
| * 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 */ |