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selftests/futex: Use thread synchronization helpers instead of usleep()

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This test uses usleep() to delay the main thread after creating the test
thread[s] under the assumption that they already are blocked on the futex
when the main thread continues.

That "works" on otherwise idle systems, but fails under load resulting in
failed selftests because the requeue operation starts before the waiters
reached the kernel.

Replace the usleep() waits by the new thread synchronization helpers to cure that.

[ tglx: Adapted to test harness changes, fixed coding style, sanitized the
	timeout handling and rewrote change log.

Co-developed-by: Edward Liaw <edliaw@google.com>
Signed-off-by: Yuwen Chen <ywen.chen@foxmail.com>
Signed-off-by: Edward Liaw <edliaw@google.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/tencent_76B9DE9C9FE5C57F6D74B5149970DF8CCF0A@qq.com
This commit is contained in:
Yuwen Chen
2026-07-20 20:58:51 +02:00
committed by Thomas Gleixner
parent 6c4a1b9726
commit 23dd3f8849
1 changed files with 28 additions and 19 deletions
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tools/testing/selftests/futex/functional/futex_requeue.c
+28 -19
View File
@@ -10,21 +10,25 @@
#include <string.h>
#include "futextest.h"
#include "futex_thread.h"
#include "kselftest_harness.h"
#define timeout_ns 30000000
#define WAKE_WAIT_US 10000
struct waiter_args {
struct __test_metadata *_metadata;
unsigned int n_threads;
};
volatile futex_t *f1;
void *waiterfn(void *arg)
static int waiterfn(void *arg)
{
struct __test_metadata *_metadata = (struct __test_metadata *)arg;
struct timespec to;
struct __test_metadata *_metadata;
struct waiter_args *wargs = arg;
struct timespec to = { };
int res;
to.tv_sec = 0;
to.tv_nsec = timeout_ns;
_metadata = wargs->_metadata;
to.tv_sec = (wargs->n_threads + 1) * WAIT_FOR_THREAD_SECS;
res = futex_wait(f1, *f1, &to, 0);
if (res) {
@@ -32,37 +36,39 @@ void *waiterfn(void *arg)
TH_LOG("waiter failed errno %d: %s", errno, strerror(errno));
}
return NULL;
return 0;
}
TEST(requeue_single)
{
struct waiter_args wargs = { ._metadata = _metadata, .n_threads = 1 };
struct futex_thread waiter;
volatile futex_t _f1 = 0;
volatile futex_t f2 = 0;
pthread_t waiter[10];
f1 = &_f1;
/*
* Requeue a waiter from f1 to f2, and wake f2.
*/
ASSERT_EQ(pthread_create(&waiter[0], NULL, waiterfn, _metadata), 0)
ASSERT_EQ(futex_thread_create(&waiter, waiterfn, &wargs), 0)
TH_LOG("pthread_create failed");
usleep(WAKE_WAIT_US);
ASSERT_EQ(futex_wait_for_thread(&waiter, _metadata), 0)
TH_LOG("Wait for thread failed");
EXPECT_EQ(futex_cmp_requeue(f1, 0, &f2, 0, 1, 0), 1);
EXPECT_EQ(futex_wake(&f2, 1, 0), 1);
pthread_join(waiter[0], NULL);
EXPECT_EQ(futex_thread_destroy(&waiter), 0);
}
TEST(requeue_multiple)
{
struct waiter_args wargs = { ._metadata = _metadata, .n_threads = 10 };
struct futex_thread waiter[10];
volatile futex_t _f1 = 0;
volatile futex_t f2 = 0;
pthread_t waiter[10];
int i;
f1 = &_f1;
@@ -70,18 +76,21 @@ TEST(requeue_multiple)
* Create 10 waiters at f1. At futex_requeue, wake 3 and requeue 7.
* At futex_wake, wake INT_MAX (should be exactly 7).
*/
for (i = 0; i < 10; i++) {
ASSERT_EQ(pthread_create(&waiter[i], NULL, waiterfn, _metadata), 0)
for (int i = 0; i < 10; i++) {
ASSERT_EQ(futex_thread_create(&waiter[i], waiterfn, &wargs), 0)
TH_LOG("pthread_create failed for waiter %d", i);
}
usleep(WAKE_WAIT_US);
for (int i = 0; i < 10; i++) {
ASSERT_EQ(futex_wait_for_thread(&waiter[i], _metadata), 0)
TH_LOG("Wait for waiter thread %d failed", i);
}
EXPECT_EQ(futex_cmp_requeue(f1, 0, &f2, 3, 7, 0), 10);
EXPECT_EQ(futex_wake(&f2, INT_MAX, 0), 7);
for (i = 0; i < 10; i++)
pthread_join(waiter[i], NULL);
for (int i = 0; i < 10; i++)
EXPECT_EQ(futex_thread_destroy(&waiter[i]), 0);
}
TEST_HARNESS_MAIN