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/*
* 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 */
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