| /* |
| * Copyright 2014 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_TFLOCK_TICKET_H |
| #define CK_TFLOCK_TICKET_H |
| |
| /* |
| * This is an implementation of task-fair locks derived from the work |
| * described in: |
| * John M. Mellor-Crummey and Michael L. Scott. 1991. |
| * Scalable reader-writer synchronization for shared-memory |
| * multiprocessors. SIGPLAN Not. 26, 7 (April 1991), 106-113. |
| */ |
| |
| #include <ck_cc.h> |
| #include <ck_pr.h> |
| |
| struct ck_tflock_ticket { |
| uint32_t request; |
| uint32_t completion; |
| }; |
| typedef struct ck_tflock_ticket ck_tflock_ticket_t; |
| |
| #define CK_TFLOCK_TICKET_INITIALIZER { 0, 0 } |
| |
| #define CK_TFLOCK_TICKET_RC_INCR 0x10000U /* Read-side increment. */ |
| #define CK_TFLOCK_TICKET_WC_INCR 0x1U /* Write-side increment. */ |
| #define CK_TFLOCK_TICKET_W_MASK 0xffffU /* Write-side mask. */ |
| #define CK_TFLOCK_TICKET_WC_TOPMSK 0x8000U /* Write clear mask for overflow. */ |
| #define CK_TFLOCK_TICKET_RC_TOPMSK 0x80000000U /* Read clear mask for overflow. */ |
| |
| CK_CC_INLINE static uint32_t |
| ck_tflock_ticket_fca_32(uint32_t *target, uint32_t mask, uint32_t delta) |
| { |
| uint32_t snapshot = ck_pr_load_32(target); |
| uint32_t goal; |
| |
| for (;;) { |
| goal = (snapshot & ~mask) + delta; |
| if (ck_pr_cas_32_value(target, snapshot, goal, &snapshot) == true) |
| break; |
| |
| ck_pr_stall(); |
| } |
| |
| return snapshot; |
| } |
| |
| CK_CC_INLINE static void |
| ck_tflock_ticket_init(struct ck_tflock_ticket *pf) |
| { |
| |
| pf->request = pf->completion = 0; |
| ck_pr_barrier(); |
| return; |
| } |
| |
| CK_CC_INLINE static void |
| ck_tflock_ticket_write_lock(struct ck_tflock_ticket *lock) |
| { |
| uint32_t previous; |
| |
| previous = ck_tflock_ticket_fca_32(&lock->request, CK_TFLOCK_TICKET_WC_TOPMSK, |
| CK_TFLOCK_TICKET_WC_INCR); |
| ck_pr_fence_atomic_load(); |
| while (ck_pr_load_32(&lock->completion) != previous) |
| ck_pr_stall(); |
| |
| ck_pr_fence_lock(); |
| return; |
| } |
| |
| CK_CC_INLINE static void |
| ck_tflock_ticket_write_unlock(struct ck_tflock_ticket *lock) |
| { |
| |
| ck_pr_fence_unlock(); |
| ck_tflock_ticket_fca_32(&lock->completion, CK_TFLOCK_TICKET_WC_TOPMSK, |
| CK_TFLOCK_TICKET_WC_INCR); |
| return; |
| } |
| |
| CK_CC_INLINE static void |
| ck_tflock_ticket_read_lock(struct ck_tflock_ticket *lock) |
| { |
| uint32_t previous; |
| |
| previous = ck_tflock_ticket_fca_32(&lock->request, |
| CK_TFLOCK_TICKET_RC_TOPMSK, CK_TFLOCK_TICKET_RC_INCR) & |
| CK_TFLOCK_TICKET_W_MASK; |
| |
| ck_pr_fence_atomic_load(); |
| |
| while ((ck_pr_load_32(&lock->completion) & |
| CK_TFLOCK_TICKET_W_MASK) != previous) { |
| ck_pr_stall(); |
| } |
| |
| ck_pr_fence_lock(); |
| return; |
| } |
| |
| CK_CC_INLINE static void |
| ck_tflock_ticket_read_unlock(struct ck_tflock_ticket *lock) |
| { |
| |
| ck_pr_fence_unlock(); |
| ck_tflock_ticket_fca_32(&lock->completion, CK_TFLOCK_TICKET_RC_TOPMSK, |
| CK_TFLOCK_TICKET_RC_INCR); |
| return; |
| } |
| |
| #endif /* CK_TFLOCK_TICKET_H */ |