[PATCH v5 2/2] selftests/futex: fix the failed futex_requeue test issue

[Yuwen Chen]

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 <ywen.c...@foxmail.com>
Co-developed-by: Edward Liaw <edl...@google.com>
Signed-off-by: Edward Liaw <edl...@google.com>
---
 .../futex/functional/futex_requeue.c          | 38 +++++++++++--------
 1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/futex/functional/futex_requeue.c 
b/tools/testing/selftests/futex/functional/futex_requeue.c
index dcf0d5f2f3122..ab87bfc4edae0 100644
--- a/tools/testing/selftests/futex/functional/futex_requeue.c
+++ b/tools/testing/selftests/futex/functional/futex_requeue.c
@@ -9,51 +9,53 @@
 #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_SECS 3
 
 volatile futex_t *f1;
 
-void *waiterfn(void *arg)
+static int waiterfn(void *arg)
 {
        struct timespec to;
 
-       to.tv_sec = 0;
-       to.tv_nsec = timeout_ns;
+       to.tv_sec = FUTEX_WAIT_TIMEOUT_SECS;
+       to.tv_nsec = 0;
 
-       if (futex_wait(f1, *f1, &to, 0))
+       if (futex_wait(f1, *f1, &to, 0)) {
                printf("waiter failed errno %d\n", errno);
+               return -errno;
+       }
 
-       return NULL;
+       return 0;
 }
 
 TEST(requeue_single)
 {
+       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(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);
 
        EXPECT_EQ(1, futex_cmp_requeue(f1, 0, &f2, 0, 1, 0));
        EXPECT_EQ(1, futex_wake(&f2, 1, 0));
+
+       EXPECT_EQ(0, futex_thread_destroy(&waiter));
 }
 
 TEST(requeue_multiple)
 {
+       struct futex_thread waiter[10];
        volatile futex_t _f1 = 0;
        volatile futex_t f2 = 0;
-       pthread_t waiter[10];
-       int i;
 
        f1 = &_f1;
 
@@ -61,13 +63,17 @@ 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]);
 
        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++)
+               EXPECT_EQ(0, futex_thread_destroy(&waiter[i]));
 }
 
 TEST_HARNESS_MAIN
-- 
2.34.1