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/*
* Copyright 2011-2015 Samy Al Bahra.
* Copyright 2011 David Joseph.
* 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.
*/
#include <ck_barrier.h>
#include <ck_cc.h>
#include <ck_pr.h>
#include <ck_spinlock.h>
#include "ck_internal.h"
void
ck_barrier_dissemination_init(struct ck_barrier_dissemination *barrier,
struct ck_barrier_dissemination_flag **barrier_internal,
unsigned int nthr)
{
unsigned int i, j, k, size, offset;
bool p = nthr & (nthr - 1);
barrier->nthr = nthr;
barrier->size = size = ck_internal_log(ck_internal_power_2(nthr));
ck_pr_store_uint(&barrier->tid, 0);
for (i = 0; i < nthr; ++i) {
barrier[i].flags[0] = barrier_internal[i];
barrier[i].flags[1] = barrier_internal[i] + size;
}
for (i = 0; i < nthr; ++i) {
for (k = 0, offset = 1; k < size; ++k, offset <<= 1) {
/*
* Determine the thread's partner, j, for the current round, k.
* Partners are chosen such that by the completion of the barrier,
* every thread has been directly (having one of its flag set) or
* indirectly (having one of its partners's flags set) signaled
* by every other thread in the barrier.
*/
if (p == false)
j = (i + offset) & (nthr - 1);
else
j = (i + offset) % nthr;
/* Set the thread's partner for round k. */
barrier[i].flags[0][k].pflag = &barrier[j].flags[0][k].tflag;
barrier[i].flags[1][k].pflag = &barrier[j].flags[1][k].tflag;
/* Set the thread's flags to false. */
barrier[i].flags[0][k].tflag = barrier[i].flags[1][k].tflag = 0;
}
}
return;
}
void
ck_barrier_dissemination_subscribe(struct ck_barrier_dissemination *barrier,
struct ck_barrier_dissemination_state *state)
{
state->parity = 0;
state->sense = ~0;
state->tid = ck_pr_faa_uint(&barrier->tid, 1);
return;
}
unsigned int
ck_barrier_dissemination_size(unsigned int nthr)
{
return (ck_internal_log(ck_internal_power_2(nthr)) << 1);
}
void
ck_barrier_dissemination(struct ck_barrier_dissemination *barrier,
struct ck_barrier_dissemination_state *state)
{
unsigned int i;
unsigned int size = barrier->size;
for (i = 0; i < size; ++i) {
unsigned int *pflag, *tflag;
pflag = barrier[state->tid].flags[state->parity][i].pflag;
tflag = &barrier[state->tid].flags[state->parity][i].tflag;
/* Unblock current partner. */
ck_pr_store_uint(pflag, state->sense);
/* Wait until some other thread unblocks this one. */
while (ck_pr_load_uint(tflag) != state->sense)
ck_pr_stall();
}
/*
* Dissemination barriers use two sets of flags to prevent race conditions
* between successive calls to the barrier. Parity indicates which set will
* be used for the next barrier. They also use a sense reversal technique
* to avoid re-initialization of the flags for every two calls to the barrier.
*/
if (state->parity == 1)
state->sense = ~state->sense;
state->parity = 1 - state->parity;
ck_pr_fence_acquire();
return;
}
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