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// SPDX-License-Identifier: GPL-2.0
#include <pthread.h>
#include <sys/shm.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <stdbool.h>
#include <time.h>
#include <assert.h>
#include "logging.h"
#include "futextest.h"
#include "futex2test.h"
typedef u_int32_t u32;
typedef int32_t s32;
typedef u_int64_t u64;
static unsigned int fflags = (FUTEX2_SIZE_U32 | FUTEX2_PRIVATE);
static int fnode = FUTEX_NO_NODE;
/* fairly stupid test-and-set lock with a waiter flag */
#define N_LOCK 0x0000001
#define N_WAITERS 0x0001000
struct futex_numa_32 {
union {
u64 full;
struct {
u32 val;
u32 node;
};
};
};
void futex_numa_32_lock(struct futex_numa_32 *lock)
{
for (;;) {
struct futex_numa_32 new, old = {
.full = __atomic_load_n(&lock->full, __ATOMIC_RELAXED),
};
for (;;) {
new = old;
if (old.val == 0) {
/* no waiter, no lock -> first lock, set no-node */
new.node = fnode;
}
if (old.val & N_LOCK) {
/* contention, set waiter */
new.val |= N_WAITERS;
}
new.val |= N_LOCK;
/* nothing changed, ready to block */
if (old.full == new.full)
break;
/*
* Use u64 cmpxchg to set the futex value and node in a
* consistent manner.
*/
if (__atomic_compare_exchange_n(&lock->full,
&old.full, new.full,
/* .weak */ false,
__ATOMIC_ACQUIRE,
__ATOMIC_RELAXED)) {
/* if we just set N_LOCK, we own it */
if (!(old.val & N_LOCK))
return;
/* go block */
break;
}
}
futex2_wait(lock, new.val, fflags, NULL, 0);
}
}
void futex_numa_32_unlock(struct futex_numa_32 *lock)
{
u32 val = __atomic_sub_fetch(&lock->val, N_LOCK, __ATOMIC_RELEASE);
assert((s32)val >= 0);
if (val & N_WAITERS) {
int woken = futex2_wake(lock, 1, fflags);
assert(val == N_WAITERS);
if (!woken) {
__atomic_compare_exchange_n(&lock->val, &val, 0U,
false, __ATOMIC_RELAXED,
__ATOMIC_RELAXED);
}
}
}
static long nanos = 50000;
struct thread_args {
pthread_t tid;
volatile int * done;
struct futex_numa_32 *lock;
int val;
int *val1, *val2;
int node;
};
static void *threadfn(void *_arg)
{
struct thread_args *args = _arg;
struct timespec ts = {
.tv_nsec = nanos,
};
int node;
while (!*args->done) {
futex_numa_32_lock(args->lock);
args->val++;
assert(*args->val1 == *args->val2);
(*args->val1)++;
nanosleep(&ts, NULL);
(*args->val2)++;
node = args->lock->node;
futex_numa_32_unlock(args->lock);
if (node != args->node) {
args->node = node;
printf("node: %d\n", node);
}
nanosleep(&ts, NULL);
}
return NULL;
}
static void *contendfn(void *_arg)
{
struct thread_args *args = _arg;
while (!*args->done) {
/*
* futex2_wait() will take hb-lock, verify *var == val and
* queue/abort. By knowingly setting val 'wrong' this will
* abort and thereby generate hb-lock contention.
*/
futex2_wait(&args->lock->val, ~0U, fflags, NULL, 0);
args->val++;
}
return NULL;
}
static volatile int done = 0;
static struct futex_numa_32 lock = { .val = 0, };
static int val1, val2;
int main(int argc, char *argv[])
{
struct thread_args *tas[512], *cas[512];
int c, t, threads = 2, contenders = 0;
int sleeps = 10;
int total = 0;
while ((c = getopt(argc, argv, "c:t:s:n:N::")) != -1) {
switch (c) {
case 'c':
contenders = atoi(optarg);
break;
case 't':
threads = atoi(optarg);
break;
case 's':
sleeps = atoi(optarg);
break;
case 'n':
nanos = atoi(optarg);
break;
case 'N':
fflags |= FUTEX2_NUMA;
if (optarg)
fnode = atoi(optarg);
break;
default:
exit(1);
break;
}
}
for (t = 0; t < contenders; t++) {
struct thread_args *args = calloc(1, sizeof(*args));
if (!args) {
perror("thread_args");
exit(-1);
}
args->done = &done;
args->lock = &lock;
args->val1 = &val1;
args->val2 = &val2;
args->node = -1;
if (pthread_create(&args->tid, NULL, contendfn, args)) {
perror("pthread_create");
exit(-1);
}
cas[t] = args;
}
for (t = 0; t < threads; t++) {
struct thread_args *args = calloc(1, sizeof(*args));
if (!args) {
perror("thread_args");
exit(-1);
}
args->done = &done;
args->lock = &lock;
args->val1 = &val1;
args->val2 = &val2;
args->node = -1;
if (pthread_create(&args->tid, NULL, threadfn, args)) {
perror("pthread_create");
exit(-1);
}
tas[t] = args;
}
sleep(sleeps);
done = true;
for (t = 0; t < threads; t++) {
struct thread_args *args = tas[t];
pthread_join(args->tid, NULL);
total += args->val;
// printf("tval: %d\n", args->val);
}
printf("total: %d\n", total);
if (contenders) {
total = 0;
for (t = 0; t < contenders; t++) {
struct thread_args *args = cas[t];
pthread_join(args->tid, NULL);
total += args->val;
// printf("tval: %d\n", args->val);
}
printf("contenders: %d\n", total);
}
return 0;
}
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