This test item has extremely high requirements for timing and can only
pass the test under specific conditions. The following situations will
lead to test failure:
MainThread Thread1
│
pthread_create-------------------┐
│ │
futex_cmp_requeue │
│ futex_wait
│ │
If the child thread is not waiting in the futex_wait function when the
main thread reaches the futex_cmp_requeue function, the test will fail.
This patch avoids this problem by checking whether the child thread is
in a sleeping state in the main thread.
Fixes: 7cb5dd8e2c8c ("selftests: futex: Add futex compare requeue test")
Signed-off-by: Yuwen Chen <[email protected]>
Co-developed-by: Edward Liaw <[email protected]>
Signed-off-by: Edward Liaw <[email protected]>
---
v1->v2:
1. Fix the issue of abnormal use of fscanf in the get_thread_state function
2. Add timeout logic
v2->v3:
https://lore.kernel.org/all/[email protected]/
1. Use /proc/[pid]/wchan instead of /proc/[pid]/stat to check if a process
has entered the sleep state
2. Refactor part of the logic to facilitate code reuse.
v3->v4:
https://lore.kernel.org/all/[email protected]/
1. Add a new futex_thread.h file.
2. Add a new function named futex_thread_destroy.
3. Fix the issue that threads are not reclaimed in futex_requeue.
.../futex/functional/futex_requeue.c | 31 +++---
.../selftests/futex/include/futex_thread.h | 100 ++++++++++++++++++
2 files changed, 118 insertions(+), 13 deletions(-)
create mode 100644 tools/testing/selftests/futex/include/futex_thread.h
diff --git a/tools/testing/selftests/futex/functional/futex_requeue.c
b/tools/testing/selftests/futex/functional/futex_requeue.c
index dcf0d5f2f3122..38743adcfd20f 100644
--- a/tools/testing/selftests/futex/functional/futex_requeue.c
+++ b/tools/testing/selftests/futex/functional/futex_requeue.c
@@ -9,10 +9,11 @@
#include <limits.h>
#include "futextest.h"
+#include "futex_thread.h"
#include "kselftest_harness.h"
-#define timeout_ns 30000000
-#define WAKE_WAIT_US 10000
+#define FUTEX_WAIT_TIMEOUT_S 3 /* 3s */
+#define WAIT_THREAD_DELAY_US (10000 * 100) /* 1s */
volatile futex_t *f1;
@@ -20,8 +21,8 @@ void *waiterfn(void *arg)
{
struct timespec to;
- to.tv_sec = 0;
- to.tv_nsec = timeout_ns;
+ to.tv_sec = FUTEX_WAIT_TIMEOUT_S;
+ to.tv_nsec = 0;
if (futex_wait(f1, *f1, &to, 0))
printf("waiter failed errno %d\n", errno);
@@ -33,27 +34,27 @@ TEST(requeue_single)
{
volatile futex_t _f1 = 0;
volatile futex_t f2 = 0;
- pthread_t waiter[10];
+ struct futex_thread waiter;
f1 = &_f1;
/*
* Requeue a waiter from f1 to f2, and wake f2.
*/
- ASSERT_EQ(0, pthread_create(&waiter[0], NULL, waiterfn, NULL));
-
- usleep(WAKE_WAIT_US);
+ ASSERT_EQ(0, futex_thread_create(&waiter, waiterfn, NULL));
+ futex_wait_for_thread(&waiter, WAIT_THREAD_DELAY_US);
EXPECT_EQ(1, futex_cmp_requeue(f1, 0, &f2, 0, 1, 0));
EXPECT_EQ(1, futex_wake(&f2, 1, 0));
+
+ futex_thread_destroy(&waiter);
}
TEST(requeue_multiple)
{
volatile futex_t _f1 = 0;
volatile futex_t f2 = 0;
- pthread_t waiter[10];
- int i;
+ struct futex_thread waiter[10];
f1 = &_f1;
@@ -61,13 +62,17 @@ 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(0, pthread_create(&waiter[i], NULL, waiterfn, NULL));
+ for (int i = 0; i < 10; i++)
+ ASSERT_EQ(0, futex_thread_create(&waiter[i], waiterfn, NULL));
- usleep(WAKE_WAIT_US);
+ for (int i = 0; i < 10; i++)
+ futex_wait_for_thread(&waiter[i], WAIT_THREAD_DELAY_US / 10);
EXPECT_EQ(10, futex_cmp_requeue(f1, 0, &f2, 3, 7, 0));
EXPECT_EQ(7, futex_wake(&f2, INT_MAX, 0));
+
+ for (int i = 0; i < 10; i++)
+ futex_thread_destroy(&waiter[i]);
}
TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/futex/include/futex_thread.h
b/tools/testing/selftests/futex/include/futex_thread.h
new file mode 100644
index 0000000000000..9761f67b6d30b
--- /dev/null
+++ b/tools/testing/selftests/futex/include/futex_thread.h
@@ -0,0 +1,100 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * library for futex tests
+ *
+ * Copyright 2026 Meizu Ltd.
+ */
+#ifndef _FUTEX_THREAD_H
+#define _FUTEX_THREAD_H
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+
+#define WAIT_THREAD_RETRIES 100
+
+struct futex_thread {
+ pthread_t thread;
+ pthread_barrier_t barrier;
+ pid_t tid;
+ void *(*threadfn)(void *);
+ void *arg;
+};
+
+static int __wait_for_thread(FILE *fp, int timeout_us)
+{
+ char buf[80] = "";
+
+ for (int i = 0; i < WAIT_THREAD_RETRIES; i++) {
+ if (!fgets(buf, sizeof(buf), fp))
+ return -EIO;
+ if (!strncmp(buf, "futex", 5))
+ return 0;
+ usleep(timeout_us / WAIT_THREAD_RETRIES);
+ rewind(fp);
+ }
+ return -ETIMEDOUT;
+}
+
+static void *__futex_thread_fn(void *arg)
+{
+ struct futex_thread *t = arg;
+
+ t->tid = gettid();
+ pthread_barrier_wait(&t->barrier);
+ return t->threadfn(t->arg);
+}
+
+/**
+ * futex_wait_for_thread - Wait for the child thread to sleep in the futex
context
+ * @t: Threads for testing.
+ * @timeout_us: Optional timeout for operation
+ */
+static inline int futex_wait_for_thread(struct futex_thread *t, int timeout_us)
+{
+ char fname[80];
+ FILE *fp;
+ int res;
+
+ snprintf(fname, sizeof(fname), "/proc/%d/wchan", t->tid);
+ fp = fopen(fname, "r");
+ if (!fp)
+ return -EIO;
+ res = __wait_for_thread(fp, timeout_us);
+ fclose(fp);
+ return res;
+}
+
+/**
+ * futex_waitv - Create thread for testing.
+ * @t: Data used for returning from the thread
+ * @threadfn: The new thread starts execution by invoking threadfn()
+ * @arg: arg is passed as the sole argument of threadfn()
+ */
+static inline int futex_thread_create(struct futex_thread *t, void
*(*threadfn)(void *), void *arg)
+{
+ int ret;
+
+ pthread_barrier_init(&t->barrier, NULL, 2);
+ t->tid = 0;
+ t->threadfn = threadfn;
+ t->arg = arg;
+
+ ret = pthread_create(&t->thread, NULL, __futex_thread_fn, t);
+ if (ret)
+ return ret;
+
+ pthread_barrier_wait(&t->barrier);
+ return 0;
+}
+
+/**
+ * futex_waitv - Destroy thread.
+ * @t: Threads for testing.
+ */
+static inline void futex_thread_destroy(struct futex_thread *t)
+{
+ pthread_join(t->thread, NULL);
+ pthread_barrier_destroy(&t->barrier);
+}
+
+#endif
--
2.34.1
