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134 lines
3.9 KiB
134 lines
3.9 KiB
/*
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* Copyright 2014 Samy Al Bahra.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef CK_TFLOCK_TICKET_H
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#define CK_TFLOCK_TICKET_H
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/*
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* This is an implementation of task-fair locks derived from the work
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* described in:
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* John M. Mellor-Crummey and Michael L. Scott. 1991.
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* Scalable reader-writer synchronization for shared-memory
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* multiprocessors. SIGPLAN Not. 26, 7 (April 1991), 106-113.
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*/
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#include <ck_cc.h>
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#include <ck_pr.h>
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struct ck_tflock_ticket {
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uint32_t request;
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uint32_t completion;
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};
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typedef struct ck_tflock_ticket ck_tflock_ticket_t;
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#define CK_TFLOCK_TICKET_INITIALIZER { 0, 0 }
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#define CK_TFLOCK_TICKET_RC_INCR 0x10000U /* Read-side increment. */
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#define CK_TFLOCK_TICKET_WC_INCR 0x1U /* Write-side increment. */
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#define CK_TFLOCK_TICKET_W_MASK 0xffffU /* Write-side mask. */
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#define CK_TFLOCK_TICKET_WC_TOPMSK 0x8000U /* Write clear mask for overflow. */
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#define CK_TFLOCK_TICKET_RC_TOPMSK 0x80000000U /* Read clear mask for overflow. */
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CK_CC_INLINE static uint32_t
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ck_tflock_ticket_fca_32(uint32_t *target, uint32_t mask, uint32_t delta)
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{
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uint32_t snapshot = ck_pr_load_32(target);
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uint32_t goal;
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for (;;) {
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goal = (snapshot & ~mask) + delta;
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if (ck_pr_cas_32_value(target, snapshot, goal, &snapshot) == true)
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break;
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ck_pr_stall();
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}
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return snapshot;
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}
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CK_CC_INLINE static void
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ck_tflock_ticket_init(struct ck_tflock_ticket *pf)
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{
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pf->request = pf->completion = 0;
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ck_pr_barrier();
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return;
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}
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CK_CC_INLINE static void
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ck_tflock_ticket_write_lock(struct ck_tflock_ticket *lock)
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{
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uint32_t previous;
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previous = ck_tflock_ticket_fca_32(&lock->request, CK_TFLOCK_TICKET_WC_TOPMSK,
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CK_TFLOCK_TICKET_WC_INCR);
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ck_pr_fence_atomic_load();
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while (ck_pr_load_32(&lock->completion) != previous)
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ck_pr_stall();
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ck_pr_fence_acquire();
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return;
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}
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CK_CC_INLINE static void
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ck_tflock_ticket_write_unlock(struct ck_tflock_ticket *lock)
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{
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ck_pr_fence_release();
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ck_tflock_ticket_fca_32(&lock->completion, CK_TFLOCK_TICKET_WC_TOPMSK,
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CK_TFLOCK_TICKET_WC_INCR);
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return;
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}
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CK_CC_INLINE static void
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ck_tflock_ticket_read_lock(struct ck_tflock_ticket *lock)
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{
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uint32_t previous;
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previous = ck_tflock_ticket_fca_32(&lock->request, CK_TFLOCK_TICKET_RC_TOPMSK,
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CK_TFLOCK_TICKET_RC_INCR) & CK_TFLOCK_TICKET_W_MASK;
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ck_pr_fence_atomic_load();
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while ((ck_pr_load_uint(&lock->completion) & CK_TFLOCK_TICKET_W_MASK) != previous)
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ck_pr_stall();
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ck_pr_fence_acquire();
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return;
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}
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CK_CC_INLINE static void
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ck_tflock_ticket_read_unlock(struct ck_tflock_ticket *lock)
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{
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ck_pr_fence_release();
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ck_tflock_ticket_fca_32(&lock->completion, CK_TFLOCK_TICKET_RC_TOPMSK,
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CK_TFLOCK_TICKET_RC_INCR);
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return;
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}
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#endif /* CK_TFLOCK_TICKET_H */
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