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141 lines
4.3 KiB
141 lines
4.3 KiB
/*
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* Copyright 2011-2015 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 <stdbool.h>
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void
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ck_barrier_mcs_init(struct ck_barrier_mcs *barrier, unsigned int nthr)
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{
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unsigned int i, j;
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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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for (j = 0; j < 4; ++j) {
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/*
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* If there are still threads that don't have parents,
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* add it as a child.
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*/
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barrier[i].havechild[j] = ((i << 2) + j < nthr - 1) ? ~0 : 0;
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/*
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* childnotready is initialized to havechild to ensure
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* a thread does not wait for a child that does not exist.
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*/
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barrier[i].childnotready[j] = barrier[i].havechild[j];
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}
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/* The root thread does not have a parent. */
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barrier[i].parent = (i == 0) ?
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&barrier[i].dummy :
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&barrier[(i - 1) >> 2].childnotready[(i - 1) & 3];
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/* Leaf threads do not have any children. */
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barrier[i].children[0] = ((i << 1) + 1 >= nthr) ?
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&barrier[i].dummy :
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&barrier[(i << 1) + 1].parentsense;
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barrier[i].children[1] = ((i << 1) + 2 >= nthr) ?
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&barrier[i].dummy :
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&barrier[(i << 1) + 2].parentsense;
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barrier[i].parentsense = 0;
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}
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return;
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}
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void
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ck_barrier_mcs_subscribe(struct ck_barrier_mcs *barrier, struct ck_barrier_mcs_state *state)
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{
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state->sense = ~0;
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state->vpid = ck_pr_faa_uint(&barrier->tid, 1);
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return;
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}
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CK_CC_INLINE static bool
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ck_barrier_mcs_check_children(unsigned int *childnotready)
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{
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if (ck_pr_load_uint(&childnotready[0]) != 0)
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return false;
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if (ck_pr_load_uint(&childnotready[1]) != 0)
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return false;
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if (ck_pr_load_uint(&childnotready[2]) != 0)
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return false;
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if (ck_pr_load_uint(&childnotready[3]) != 0)
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return false;
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return true;
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}
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CK_CC_INLINE static void
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ck_barrier_mcs_reinitialize_children(struct ck_barrier_mcs *node)
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{
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ck_pr_store_uint(&node->childnotready[0], node->havechild[0]);
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ck_pr_store_uint(&node->childnotready[1], node->havechild[1]);
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ck_pr_store_uint(&node->childnotready[2], node->havechild[2]);
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ck_pr_store_uint(&node->childnotready[3], node->havechild[3]);
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return;
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}
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void
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ck_barrier_mcs(struct ck_barrier_mcs *barrier,
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struct ck_barrier_mcs_state *state)
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{
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/*
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* Wait until all children have reached the barrier and are done waiting
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* for their children.
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*/
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while (ck_barrier_mcs_check_children(barrier[state->vpid].childnotready) == false)
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ck_pr_stall();
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/* Reinitialize for next barrier. */
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ck_barrier_mcs_reinitialize_children(&barrier[state->vpid]);
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/* Inform parent thread and its children have arrived at the barrier. */
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ck_pr_store_uint(barrier[state->vpid].parent, 0);
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/* Wait until parent indicates all threads have arrived at the barrier. */
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if (state->vpid != 0) {
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while (ck_pr_load_uint(&barrier[state->vpid].parentsense) != state->sense)
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ck_pr_stall();
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}
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/* Inform children of successful barrier. */
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ck_pr_store_uint(barrier[state->vpid].children[0], state->sense);
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ck_pr_store_uint(barrier[state->vpid].children[1], state->sense);
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state->sense = ~state->sense;
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return;
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}
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