1 /* 2 * Copyright 2010-2015 Samy Al Bahra. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27 #ifndef CK_SPINLOCK_CLH_H 28 #define CK_SPINLOCK_CLH_H 29 30 #include <ck_cc.h> 31 #include <ck_limits.h> 32 #include <ck_pr.h> 33 #include <ck_stdbool.h> 34 #include <ck_stddef.h> 35 36 #ifndef CK_F_SPINLOCK_CLH 37 #define CK_F_SPINLOCK_CLH 38 39 struct ck_spinlock_clh { 40 unsigned int wait; 41 struct ck_spinlock_clh *previous; 42 }; 43 typedef struct ck_spinlock_clh ck_spinlock_clh_t; 44 45 CK_CC_INLINE static void 46 ck_spinlock_clh_init(struct ck_spinlock_clh **lock, struct ck_spinlock_clh *unowned) 47 { 48 49 unowned->previous = NULL; 50 unowned->wait = false; 51 *lock = unowned; 52 ck_pr_barrier(); 53 return; 54 } 55 56 CK_CC_INLINE static bool 57 ck_spinlock_clh_locked(struct ck_spinlock_clh **queue) 58 { 59 struct ck_spinlock_clh *head; 60 bool r; 61 62 head = ck_pr_load_ptr(queue); 63 r = ck_pr_load_uint(&head->wait); 64 ck_pr_fence_acquire(); 65 return r; 66 } 67 68 CK_CC_INLINE static void 69 ck_spinlock_clh_lock(struct ck_spinlock_clh **queue, struct ck_spinlock_clh *thread) 70 { 71 struct ck_spinlock_clh *previous; 72 73 /* Indicate to the next thread on queue that they will have to block. */ 74 thread->wait = true; 75 ck_pr_fence_store_atomic(); 76 77 /* 78 * Mark current request as last request. Save reference to previous 79 * request. 80 */ 81 previous = ck_pr_fas_ptr(queue, thread); 82 thread->previous = previous; 83 84 /* Wait until previous thread is done with lock. */ 85 ck_pr_fence_load(); 86 while (ck_pr_load_uint(&previous->wait) == true) 87 ck_pr_stall(); 88 89 ck_pr_fence_lock(); 90 return; 91 } 92 93 CK_CC_INLINE static void 94 ck_spinlock_clh_unlock(struct ck_spinlock_clh **thread) 95 { 96 struct ck_spinlock_clh *previous; 97 98 /* 99 * If there are waiters, they are spinning on the current node wait 100 * flag. The flag is cleared so that the successor may complete an 101 * acquisition. If the caller is pre-empted then the predecessor field 102 * may be updated by a successor's lock operation. In order to avoid 103 * this, save a copy of the predecessor before setting the flag. 104 */ 105 previous = thread[0]->previous; 106 107 /* 108 * We have to pay this cost anyways, use it as a compiler barrier too. 109 */ 110 ck_pr_fence_unlock(); 111 ck_pr_store_uint(&(*thread)->wait, false); 112 113 /* 114 * Predecessor is guaranteed not to be spinning on previous request, 115 * so update caller to use previous structure. This allows successor 116 * all the time in the world to successfully read updated wait flag. 117 */ 118 *thread = previous; 119 return; 120 } 121 #endif /* CK_F_SPINLOCK_CLH */ 122 #endif /* CK_SPINLOCK_CLH_H */ 123