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Diffstat (limited to 'sys/contrib/ck/include/ck_tflock.h')
| -rw-r--r-- | sys/contrib/ck/include/ck_tflock.h | 136 |
1 files changed, 136 insertions, 0 deletions
diff --git a/sys/contrib/ck/include/ck_tflock.h b/sys/contrib/ck/include/ck_tflock.h new file mode 100644 index 000000000000..a1872ae08ac8 --- /dev/null +++ b/sys/contrib/ck/include/ck_tflock.h @@ -0,0 +1,136 @@ +/* + * 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 */ |