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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_pr.h>
#include "ck_internal.h"
/*
* This is a tournament barrier implementation. Threads are statically
* assigned roles to perform for each round of the barrier. Winners
* move on to the next round, while losers spin in their current rounds
* on their own flags. During the last round, the champion of the tournament
* sets the last flag that begins the wakeup process.
*/
enum {
CK_BARRIER_TOURNAMENT_BYE,
CK_BARRIER_TOURNAMENT_CHAMPION,
CK_BARRIER_TOURNAMENT_DROPOUT,
CK_BARRIER_TOURNAMENT_LOSER,
CK_BARRIER_TOURNAMENT_WINNER
};
void
ck_barrier_tournament_subscribe(struct ck_barrier_tournament *barrier,
struct ck_barrier_tournament_state *state)
{
state->sense = ~0;
state->vpid = ck_pr_faa_uint(&barrier->tid, 1);
return;
}
void
ck_barrier_tournament_init(struct ck_barrier_tournament *barrier,
struct ck_barrier_tournament_round **rounds,
unsigned int nthr)
{
unsigned int i, k, size, twok, twokm1, imod2k;
ck_pr_store_uint(&barrier->tid, 0);
barrier->size = size = ck_barrier_tournament_size(nthr);
for (i = 0; i < nthr; ++i) {
/* The first role is always CK_BARRIER_TOURNAMENT_DROPOUT. */
rounds[i][0].flag = 0;
rounds[i][0].role = CK_BARRIER_TOURNAMENT_DROPOUT;
for (k = 1, twok = 2, twokm1 = 1; k < size; ++k, twokm1 = twok, twok <<= 1) {
rounds[i][k].flag = 0;
imod2k = i & (twok - 1);
if (imod2k == 0) {
if ((i + twokm1 < nthr) && (twok < nthr))
rounds[i][k].role = CK_BARRIER_TOURNAMENT_WINNER;
else if (i + twokm1 >= nthr)
rounds[i][k].role = CK_BARRIER_TOURNAMENT_BYE;
}
if (imod2k == twokm1)
rounds[i][k].role = CK_BARRIER_TOURNAMENT_LOSER;
else if ((i == 0) && (twok >= nthr))
rounds[i][k].role = CK_BARRIER_TOURNAMENT_CHAMPION;
if (rounds[i][k].role == CK_BARRIER_TOURNAMENT_LOSER)
rounds[i][k].opponent = &rounds[i - twokm1][k].flag;
else if (rounds[i][k].role == CK_BARRIER_TOURNAMENT_WINNER ||
rounds[i][k].role == CK_BARRIER_TOURNAMENT_CHAMPION)
rounds[i][k].opponent = &rounds[i + twokm1][k].flag;
}
}
ck_pr_store_ptr(&barrier->rounds, rounds);
return;
}
unsigned int
ck_barrier_tournament_size(unsigned int nthr)
{
return (ck_internal_log(ck_internal_power_2(nthr)) + 1);
}
void
ck_barrier_tournament(struct ck_barrier_tournament *barrier,
struct ck_barrier_tournament_state *state)
{
struct ck_barrier_tournament_round **rounds = ck_pr_load_ptr(&barrier->rounds);
int round = 1;
if (barrier->size == 1)
return;
for (;; ++round) {
switch (rounds[state->vpid][round].role) {
case CK_BARRIER_TOURNAMENT_BYE:
break;
case CK_BARRIER_TOURNAMENT_CHAMPION:
/*
* The CK_BARRIER_TOURNAMENT_CHAMPION waits until it wins the tournament; it then
* sets the final flag before the wakeup phase of the barrier.
*/
while (ck_pr_load_uint(&rounds[state->vpid][round].flag) != state->sense)
ck_pr_stall();
ck_pr_store_uint(rounds[state->vpid][round].opponent, state->sense);
goto wakeup;
case CK_BARRIER_TOURNAMENT_DROPOUT:
/* NOTREACHED */
break;
case CK_BARRIER_TOURNAMENT_LOSER:
/*
* CK_BARRIER_TOURNAMENT_LOSERs set the flags of their opponents and wait until
* their opponents release them after the tournament is over.
*/
ck_pr_store_uint(rounds[state->vpid][round].opponent, state->sense);
while (ck_pr_load_uint(&rounds[state->vpid][round].flag) != state->sense)
ck_pr_stall();
goto wakeup;
case CK_BARRIER_TOURNAMENT_WINNER:
/*
* CK_BARRIER_TOURNAMENT_WINNERs wait until their current opponent sets their flag; they then
* continue to the next round of the tournament.
*/
while (ck_pr_load_uint(&rounds[state->vpid][round].flag) != state->sense)
ck_pr_stall();
break;
}
}
wakeup:
for (round -= 1 ;; --round) {
switch (rounds[state->vpid][round].role) {
case CK_BARRIER_TOURNAMENT_BYE:
break;
case CK_BARRIER_TOURNAMENT_CHAMPION:
/* NOTREACHED */
break;
case CK_BARRIER_TOURNAMENT_DROPOUT:
goto leave;
break;
case CK_BARRIER_TOURNAMENT_LOSER:
/* NOTREACHED */
break;
case CK_BARRIER_TOURNAMENT_WINNER:
/*
* Winners inform their old opponents the tournament is over
* by setting their flags.
*/
ck_pr_store_uint(rounds[state->vpid][round].opponent, state->sense);
break;
}
}
leave:
ck_pr_fence_memory();
state->sense = ~state->sense;
return;
}
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