Branch
Hash :
7b089321
Author :
Date :
2025-01-01T09:24:36
maint: run 'make update-copyright'
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234
/* Test of simple atomic operations for multithreading.
Copyright (C) 2021-2025 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2021. */
#include <config.h>
#include "simple-atomic.h"
#if USE_ISOC_THREADS || USE_POSIX_THREADS || USE_ISOC_AND_POSIX_THREADS || USE_WINDOWS_THREADS
/* Whether to help the scheduler through explicit yield().
Uncomment this to see if the operating system has a fair scheduler. */
#define EXPLICIT_YIELD 1
/* Number of simultaneous threads. */
#define THREAD_COUNT 4
/* Number of operations performed in each thread.
With a smaller count, say 100, we often get an "OK" result even with the racy
implementation. */
#define REPEAT_COUNT 1000
#include "glthread/thread.h"
#include "glthread/yield.h"
#include "macros.h"
#if EXPLICIT_YIELD
# define yield() gl_thread_yield ()
#else
# define yield()
#endif
/* Counters for each thread. */
static unsigned int counter[THREAD_COUNT][5];
/* A variable of type 'unsigned int'. */
static unsigned int int_variable;
static void *
int_mutator_thread (void *arg)
{
int *pcounter = (int *) arg;
int repeat;
for (repeat = REPEAT_COUNT; repeat > 0; repeat--)
{
if (atomic_compare_and_swap (&int_variable, 0, 10) == 0)
pcounter[0]++;
yield ();
if (atomic_compare_and_swap (&int_variable, 14, 17) == 14)
pcounter[1]++;
yield ();
if (atomic_compare_and_swap (&int_variable, 20, 0) == 20)
pcounter[2]++;
yield ();
if (atomic_compare_and_swap (&int_variable, 10, 14) == 10)
pcounter[3]++;
yield ();
if (atomic_compare_and_swap (&int_variable, 17, 20) == 17)
pcounter[4]++;
yield ();
}
return NULL;
}
/* A variable of type 'uintptr_t'. */
static uintptr_t ptr_variable;
static void *
ptr_mutator_thread (void *arg)
{
int *pcounter = (int *) arg;
int repeat;
for (repeat = REPEAT_COUNT; repeat > 0; repeat--)
{
if (atomic_compare_and_swap_ptr (&ptr_variable, 0, 10) == 0)
pcounter[0]++;
yield ();
if (atomic_compare_and_swap_ptr (&ptr_variable, 14, 17) == 14)
pcounter[1]++;
yield ();
if (atomic_compare_and_swap_ptr (&ptr_variable, 20, 0) == 20)
pcounter[2]++;
yield ();
if (atomic_compare_and_swap_ptr (&ptr_variable, 10, 14) == 10)
pcounter[3]++;
yield ();
if (atomic_compare_and_swap_ptr (&ptr_variable, 17, 20) == 17)
pcounter[4]++;
yield ();
}
return NULL;
}
int
main ()
{
/* Check simple uses of atomic_compare_and_swap. */
{
unsigned int x[3] = { 0xDEADBEEFU, 11, 0xDEADBEEFU };
ASSERT (atomic_compare_and_swap (&x[1], 0, 17) == 11);
ASSERT (x[1] == 11);
ASSERT (atomic_compare_and_swap (&x[1], 4, 11) == 11);
ASSERT (x[1] == 11);
ASSERT (atomic_compare_and_swap (&x[1], 11, 15) == 11);
ASSERT (x[1] == 15);
ASSERT (x[0] == 0xDEADBEEFU);
ASSERT (x[2] == 0xDEADBEEFU);
}
/* Check simple uses of atomic_compare_and_swap_ptr. */
{
uintptr_t v1 = ~(uintptr_t)0 / 3;
uintptr_t v2 = ~(uintptr_t)0 / 5 * 4;
uintptr_t v3 = ~(uintptr_t)0 / 7 * 3;
uintptr_t x[3] = { 0xDEADBEEFU, v1, 0xDEADBEEFU };
ASSERT (atomic_compare_and_swap_ptr (&x[1], 0, v3) == v1);
ASSERT (x[1] == v1);
ASSERT (atomic_compare_and_swap_ptr (&x[1], 4, v1) == v1);
ASSERT (x[1] == v1);
ASSERT (atomic_compare_and_swap_ptr (&x[1], v1, v2) == v1);
ASSERT (x[1] == v2);
ASSERT (x[0] == 0xDEADBEEFU);
ASSERT (x[2] == 0xDEADBEEFU);
}
/* Check atomicity of atomic_compare_and_swap. */
{
void * (*funcs[2]) (void *) = { int_mutator_thread, ptr_mutator_thread };
int f;
for (f = 0; f < 2; f++)
{
void * (*func) (void *) = funcs[f];
int i, j;
gl_thread_t threads[THREAD_COUNT];
/* Initialization. */
for (i = 0; i < THREAD_COUNT; i++)
for (j = 0; j < 5; j++)
counter[i][j] = 0;
/* Spawn the threads. */
for (i = 0; i < THREAD_COUNT; i++)
threads[i] = gl_thread_create (func, &counter[i][0]);
/* Wait for the threads to terminate. */
for (i = 0; i < THREAD_COUNT; i++)
gl_thread_join (threads[i], NULL);
/* Sum up the work that the threads have done. */
unsigned int sum[5];
for (j = 0; j < 5; j++)
{
sum[j] = 0;
for (i = 0; i < THREAD_COUNT; i++)
sum[j] += counter[i][j];
}
/* If things went atomically, the threads have moved the variable's
value through the cycle 0 -> 10 -> 14 -> 17 -> 20 -> 0 ... a large
number of times.
sum[0] is the number of transitions 0 -> 10.
sum[3] is the number of transitions 10 -> 14.
sum[1] is the number of transitions 14 -> 17.
sum[4] is the number of transitions 17 -> 20.
sum[2] is the number of transitions 20 -> 0.
Since the cycle started at 0 and ends anywhere (namely, when all
threads when through their loop REPEAT_COUNT times), the sequence
sum[0], sum[3], sum[1], sum[4], sum[2], sum[0] - 1
must be monotonically decreasing.
If things did not go atomically, the counters don't exhibit this
pattern. */
printf ("Counters: %u %u %u %u %u\n",
sum[0], sum[3], sum[1], sum[4], sum[2]);
ASSERT ((sum[0] == sum[3] || sum[0] == sum[3] + 1)
&& (sum[3] == sum[1] || sum[3] == sum[1] + 1)
&& (sum[1] == sum[4] || sum[1] == sum[4] + 1)
&& (sum[4] == sum[2] || sum[4] == sum[2] + 1)
&& (sum[2] + 1 == sum[0] || sum[2] == sum[0]));
}
}
return test_exit_status;
}
#else
/* No multithreading available. */
#include <stdio.h>
int
main ()
{
fputs ("Skipping test: multithreading not enabled\n", stderr);
return 77;
}
#endif