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125 lines
4.0 KiB
125 lines
4.0 KiB
/*
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* Copyright 2011 Samy Al Bahra.
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* Copyright 2011 David Joseph.
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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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#include <ck_barrier.h>
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#include <ck_cc.h>
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#include <ck_pr.h>
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#include <ck_spinlock.h>
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#include "ck_internal.h"
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void
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ck_barrier_dissemination_init(struct ck_barrier_dissemination *barrier,
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struct ck_barrier_dissemination_flag **barrier_internal,
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unsigned int nthr)
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{
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unsigned int i, j, k, size, offset;
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bool p = nthr & (nthr - 1);
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barrier->nthr = nthr;
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barrier->size = size = ck_internal_log(ck_internal_power_2(nthr));
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ck_pr_store_uint(&barrier->tid, 0);
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for (i = 0; i < nthr; ++i) {
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barrier[i].flags[0] = barrier_internal[i];
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barrier[i].flags[1] = barrier_internal[i] + size;
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}
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for (i = 0; i < nthr; ++i) {
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for (k = 0, offset = 1; k < size; ++k, offset <<= 1) {
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/*
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* Determine the thread's partner, j, for the current round, k.
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* Partners are chosen such that by the completion of the barrier,
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* every thread has been directly (having one of its flag set) or
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* indirectly (having one of its partners's flags set) signaled
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* by every other thread in the barrier.
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*/
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if (p == false)
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j = (i + offset) & (nthr - 1);
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else
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j = (i + offset) % nthr;
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/* Set the thread's partner for round k. */
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barrier[i].flags[0][k].pflag = &barrier[j].flags[0][k].tflag;
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barrier[i].flags[1][k].pflag = &barrier[j].flags[1][k].tflag;
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/* Set the thread's flags to false. */
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barrier[i].flags[0][k].tflag = barrier[i].flags[1][k].tflag = 0;
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}
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}
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return;
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}
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void
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ck_barrier_dissemination_subscribe(struct ck_barrier_dissemination *barrier,
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struct ck_barrier_dissemination_state *state)
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{
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state->parity = 0;
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state->sense = ~0;
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state->tid = ck_pr_faa_uint(&barrier->tid, 1);
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return;
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}
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unsigned int
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ck_barrier_dissemination_size(unsigned int nthr)
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{
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return (ck_internal_log(ck_internal_power_2(nthr)) << 1);
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}
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void
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ck_barrier_dissemination(struct ck_barrier_dissemination *barrier,
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struct ck_barrier_dissemination_state *state)
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{
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unsigned int i;
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unsigned int size = barrier->size;
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for (i = 0; i < size; ++i) {
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/* Unblock current partner. */
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ck_pr_store_uint(barrier[state->tid].flags[state->parity][i].pflag, state->sense);
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/* Wait until some other thread unblocks this one. */
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while (ck_pr_load_uint(&barrier[state->tid].flags[state->parity][i].tflag) != state->sense)
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ck_pr_stall();
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}
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/*
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* Dissemination barriers use two sets of flags to prevent race conditions
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* between successive calls to the barrier. Parity indicates which set will
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* be used for the next barrier. They also use a sense reversal technique
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* to avoid re-initialization of the flags for every two calls to the barrier.
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*/
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if (state->parity == 1)
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state->sense = ~state->sense;
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state->parity = 1 - state->parity;
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return;
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}
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