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