[PATCH v2 0/5] selftests/futex: fix the issue of abnormal test results caused by thread timing

[PATCH v2 0/5] selftests/futex: fix the issue of abnormal test results caused by thread timing

[Yuwen Chen]

On the Android arm32 platform, when performing the futex_requeue test, it will
most likely return a failure. The specific reason is detailed in a commit[1]
previously submitted by Edward Liaw. However, this commit cannot perfectly
solve the problem. This is because using a barrier does not guarantee that
the child thread will wait on futex_wait.

This series of patches attempts to solve this problem by checking whether
the child thread is in a sleeping state. This is because when the child thread
goes to sleep, it indicates that it is waiting for the futex lock.

v1->v2:
    - Solve the compilation problems found by the kernel test robot
    - Cleanup the atomic library code for futex test

Link: https://lore.kernel.org/all/20240918231102.234253-1-edliaw@google.com/

[PATCH v2 1/5] selftests/futex: reduce array declarations in the requeue_single

[Yuwen Chen]

In the requeue_single function, the variable "waits" only uses
one element. There is no need to use an array.

Signed-off-by: Yuwen Chen <ywen.chen@foxmail.com>
---
 tools/testing/selftests/futex/functional/futex_requeue.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/futex/functional/futex_requeue.c b/tools/testing/selftests/futex/functional/futex_requeue.c
index 69e2555b60399..1807465de2144 100644
--- a/tools/testing/selftests/futex/functional/futex_requeue.c
+++ b/tools/testing/selftests/futex/functional/futex_requeue.c
@@ -33,7 +33,7 @@ TEST(requeue_single)
 {
 	volatile futex_t _f1 = 0;
 	volatile futex_t f2 = 0;
-	pthread_t waiter[10];
+	pthread_t waiter;
 	int res;
 
 	f1 = &_f1;
@@ -41,7 +41,7 @@ TEST(requeue_single)
 	/*
 	 * Requeue a waiter from f1 to f2, and wake f2.
 	 */
-	if (pthread_create(&waiter[0], NULL, waiterfn, NULL))
+	if (pthread_create(&waiter, NULL, waiterfn, NULL))
 		ksft_exit_fail_msg("pthread_create failed\n");
 
 	usleep(WAKE_WAIT_US);
-- 
2.34.1

[PATCH v2 1/5] selftests/futex: reduce array declarations in the requeue_single

[Licay]

> In the requeue_single function, the variable "waits" only uses
> one element. There is no need to use an array.
>
> Signed-off-by: Yuwen Chen <ywen.chen@foxmail.com>

Reviewed-by: Licay <licayy@foxmail.com>
> ---
>  tools/testing/selftests/futex/functional/futex_requeue.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/futex/functional/futex_requeue.c b/tools/testing/selftests/futex/functional/futex_requeue.c
> index 69e2555b60399..1807465de2144 100644
> --- a/tools/testing/selftests/futex/functional/futex_requeue.c
> +++ b/tools/testing/selftests/futex/functional/futex_requeue.c
> @@ -33,7 +33,7 @@ TEST(requeue_single)
>  {
>          volatile futex_t _f1 = 0;
>          volatile futex_t f2 = 0;
> -        pthread_t waiter[10];
> +        pthread_t waiter;
>          int res;
>
>          f1 = &_f1;
> @@ -41,7 +41,7 @@ TEST(requeue_single)
>          /*
>           * Requeue a waiter from f1 to f2, and wake f2.
>           */
> -        if (pthread_create(&waiter[0], NULL, waiterfn, NULL))
> +        if (pthread_create(&waiter, NULL, waiterfn, NULL))
>                  ksft_exit_fail_msg("pthread_create failed\n");
>
>          usleep(WAKE_WAIT_US);
> --
> 2.34.1

[PATCH v2 2/5] selftests/futex: use pthread_join to reclaim thread resources

[Yuwen Chen]

When creating a thread using pthread_create, you should use
pthread_join to free its resources.

Signed-off-by: Yuwen Chen <ywen.chen@foxmail.com>
---
 tools/testing/selftests/futex/functional/futex_requeue.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/testing/selftests/futex/functional/futex_requeue.c b/tools/testing/selftests/futex/functional/futex_requeue.c
index 1807465de2144..7a22458c7fc96 100644
--- a/tools/testing/selftests/futex/functional/futex_requeue.c
+++ b/tools/testing/selftests/futex/functional/futex_requeue.c
@@ -62,6 +62,8 @@ TEST(requeue_single)
 	} else {
 		ksft_test_result_pass("futex_requeue simple succeeds\n");
 	}
+
+	pthread_join(waiter, NULL);
 }
 
 TEST(requeue_multiple)
@@ -101,6 +103,9 @@ TEST(requeue_multiple)
 	} else {
 		ksft_test_result_pass("futex_requeue many succeeds\n");
 	}
+
+	for (i = 0; i < 10; i++)
+		pthread_join(waiter[i], NULL);
 }
 
 TEST_HARNESS_MAIN
-- 
2.34.1

[PATCH v2 2/5] selftests/futex: use pthread_join to reclaim thread resources

[Licay]

> When creating a thread using pthread_create, you should use
> pthread_join to free its resources.
>
> Signed-off-by: Yuwen Chen <ywen.chen@foxmail.com>
Reviewed-by: Licay <licayy@foxmail.com>
> ---
>  tools/testing/selftests/futex/functional/futex_requeue.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/tools/testing/selftests/futex/functional/futex_requeue.c b/tools/testing/selftests/futex/functional/futex_requeue.c
> index 1807465de2144..7a22458c7fc96 100644
> --- a/tools/testing/selftests/futex/functional/futex_requeue.c
> +++ b/tools/testing/selftests/futex/functional/futex_requeue.c
> @@ -62,6 +62,8 @@ TEST(requeue_single)
>  	} else {
>  		ksft_test_result_pass("futex_requeue simple succeeds\n");
>  	}
> +
> +	pthread_join(waiter, NULL);
>  }
>
>  TEST(requeue_multiple)
> @@ -101,6 +103,9 @@ TEST(requeue_multiple)
>  	} else {
>  		ksft_test_result_pass("futex_requeue many succeeds\n");
>  	}
> +
> +	for (i = 0; i < 10; i++)
> +		pthread_join(waiter[i], NULL);
>  }
>
>  TEST_HARNESS_MAIN
> --
> 2.34.1
>

[PATCH v2 3/5] selftests/futex: read atomic variable value with atomic_read

[Yuwen Chen]

Directly reading the internal value of atomic_t externally does
not meet the encapsulation requirements. A new function
atomic_read is added to obtain the value of an atomic variable.

Signed-off-by: Yuwen Chen <ywen.chen@foxmail.com>
---
 .../selftests/futex/functional/futex_requeue_pi.c    | 12 ++++++------
 .../functional/futex_requeue_pi_signal_restart.c     |  4 ++--
 tools/testing/selftests/futex/include/atomic.h       | 12 ++++++++++++
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/futex/functional/futex_requeue_pi.c b/tools/testing/selftests/futex/functional/futex_requeue_pi.c
index f299d75848cd4..5d845b052891b 100644
--- a/tools/testing/selftests/futex/functional/futex_requeue_pi.c
+++ b/tools/testing/selftests/futex/functional/futex_requeue_pi.c
@@ -201,7 +201,7 @@ void *broadcast_wakerfn(void *arg)
 	int i = 0;
 
 	ksft_print_dbg_msg("Waker: waiting for waiters to block\n");
-	while (waiters_blocked.val < THREAD_MAX)
+	while (atomic_read(&waiters_blocked) < THREAD_MAX)
 		usleep(1000);
 	usleep(1000);
 
@@ -218,7 +218,7 @@ void *broadcast_wakerfn(void *arg)
 		ksft_exit_fail_msg("FUTEX_CMP_REQUEUE_PI failed\n");
 	} else if (++i < MAX_WAKE_ITERS) {
 		task_count += args->ret;
-		if (task_count < THREAD_MAX - waiters_woken.val)
+		if (task_count < THREAD_MAX - atomic_read(&waiters_woken))
 			goto continue_requeue;
 	} else {
 		ksft_exit_fail_msg("max broadcast iterations (%d) reached with %d/%d tasks woken or requeued\n",
@@ -247,13 +247,13 @@ void *signal_wakerfn(void *arg)
 	int i = 0;
 
 	ksft_print_dbg_msg("Waker: waiting for waiters to block\n");
-	while (waiters_blocked.val < THREAD_MAX)
+	while (atomic_read(&waiters_blocked) < THREAD_MAX)
 		usleep(1000);
 	usleep(1000);
 
-	while (task_count < THREAD_MAX && waiters_woken.val < THREAD_MAX) {
+	while (task_count < THREAD_MAX && atomic_read(&waiters_woken) < THREAD_MAX) {
 		ksft_print_dbg_msg("task_count: %d, waiters_woken: %d\n",
-		     task_count, waiters_woken.val);
+		     task_count, atomic_read(&waiters_woken));
 		if (args->lock) {
 			ksft_print_dbg_msg("Calling FUTEX_LOCK_PI on mutex=%x @ %p\n",
 			    f2, &f2);
@@ -293,7 +293,7 @@ void *signal_wakerfn(void *arg)
 		args->ret = task_count;
 
 	ksft_print_dbg_msg("Waker: exiting with %d\n", args->ret);
-	ksft_print_dbg_msg("Waker: waiters_woken: %d\n", waiters_woken.val);
+	ksft_print_dbg_msg("Waker: waiters_woken: %d\n", atomic_read(&waiters_woken));
 	pthread_exit((void *)&args->ret);
 }
 
diff --git a/tools/testing/selftests/futex/functional/futex_requeue_pi_signal_restart.c b/tools/testing/selftests/futex/functional/futex_requeue_pi_signal_restart.c
index e34ee0f9ebccd..29f93916b46da 100644
--- a/tools/testing/selftests/futex/functional/futex_requeue_pi_signal_restart.c
+++ b/tools/testing/selftests/futex/functional/futex_requeue_pi_signal_restart.c
@@ -70,7 +70,7 @@ int create_rt_thread(pthread_t *pth, void*(*func)(void *), void *arg,
 void handle_signal(int signo)
 {
 	ksft_print_dbg_msg("signal received %s requeue\n",
-	     requeued.val ? "after" : "prior to");
+	     atomic_read(&requeued) ? "after" : "prior to");
 }
 
 void *waiterfn(void *arg)
@@ -83,7 +83,7 @@ void *waiterfn(void *arg)
 	old_val = f1;
 	res = futex_wait_requeue_pi(&f1, old_val, &(f2), NULL,
 				    FUTEX_PRIVATE_FLAG);
-	if (!requeued.val || errno != EWOULDBLOCK) {
+	if (!atomic_read(&requeued) || errno != EWOULDBLOCK) {
 		ksft_test_result_fail("unexpected return from futex_wait_requeue_pi: %d (%s)\n",
 		     res, strerror(errno));
 		ksft_print_dbg_msg("w2:futex: %x\n", f2);
diff --git a/tools/testing/selftests/futex/include/atomic.h b/tools/testing/selftests/futex/include/atomic.h
index 428bcd921bb53..c0dccb1b966ba 100644
--- a/tools/testing/selftests/futex/include/atomic.h
+++ b/tools/testing/selftests/futex/include/atomic.h
@@ -76,4 +76,16 @@ atomic_set(atomic_t *addr, int newval)
 	return newval;
 }
 
+/**
+ * atomic_read() - Atomic read
+ * @addr:	Address of the variable to read
+ *
+ * Return the value of addr->val.
+ */
+static inline int
+atomic_read(atomic_t *addr)
+{
+	return addr->val;
+}
+
 #endif
-- 
2.34.1

[PATCH v2 3/5] selftests/futex: read atomic variable value with atomic_read

[Licay]

> Directly reading the internal value of atomic_t externally does
> not meet the encapsulation requirements. A new function
> atomic_read is added to obtain the value of an atomic variable.
>
> Signed-off-by: Yuwen Chen <ywen.chen@foxmail.com>
> ---
>  .../selftests/futex/functional/futex_requeue_pi.c    | 12 ++++++------
>  .../functional/futex_requeue_pi_signal_restart.c     |  4 ++--
>  tools/testing/selftests/futex/include/atomic.h       | 12 ++++++++++++
>  3 files changed, 20 insertions(+), 8 deletions(-)
Reviewed-by: Licay <licayy@foxmail.com>

[PATCH v2 4/5] selftests/futex: introduce the declaration of atomic_t from types.h

[Yuwen Chen]

Introduce the header files specifically prepared for test programs
from the tools/include directory. And solve the problem that
atomic_read and atomic_set may not be safe in a multi - threaded
environment.

Signed-off-by: Yuwen Chen <ywen.chen@foxmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202512112344.gsyPl2ag-lkp@intel.com/
---
 .../selftests/futex/functional/Makefile       |  2 +-
 .../testing/selftests/futex/include/atomic.h  | 25 +++++++++----------
 2 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/tools/testing/selftests/futex/functional/Makefile b/tools/testing/selftests/futex/functional/Makefile
index 490ace1f017e8..8589917a4b126 100644
--- a/tools/testing/selftests/futex/functional/Makefile
+++ b/tools/testing/selftests/futex/functional/Makefile
@@ -2,7 +2,7 @@
 PKG_CONFIG ?= pkg-config
 LIBNUMA_TEST = $(shell sh -c "$(PKG_CONFIG) numa --atleast-version 2.0.16 > /dev/null 2>&1 && echo SUFFICIENT || echo NO")
 
-INCLUDES := -I../include -I../../ $(KHDR_INCLUDES)
+INCLUDES := -I../include -I../../ $(KHDR_INCLUDES) -I../../../../include
 CFLAGS := $(CFLAGS) -g -O2 -Wall -pthread -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64 $(INCLUDES) $(KHDR_INCLUDES) -DLIBNUMA_VER_$(LIBNUMA_TEST)=1
 LDLIBS := -lpthread -lrt -lnuma
 
diff --git a/tools/testing/selftests/futex/include/atomic.h b/tools/testing/selftests/futex/include/atomic.h
index c0dccb1b966ba..b23e1a50949a7 100644
--- a/tools/testing/selftests/futex/include/atomic.h
+++ b/tools/testing/selftests/futex/include/atomic.h
@@ -18,9 +18,8 @@
 #ifndef _ATOMIC_H
 #define _ATOMIC_H
 
-typedef struct {
-	volatile int val;
-} atomic_t;
+#include <linux/types.h>
+#include <linux/compiler.h>
 
 #define ATOMIC_INITIALIZER { 0 }
 
@@ -30,36 +29,36 @@ typedef struct {
  * @oldval:	The expected value of the futex
  * @newval:	The new value to try and assign the futex
  *
- * Return the old value of addr->val.
+ * Return the old value of addr->counter.
  */
 static inline int
 atomic_cmpxchg(atomic_t *addr, int oldval, int newval)
 {
-	return __sync_val_compare_and_swap(&addr->val, oldval, newval);
+	return __sync_val_compare_and_swap(&addr->counter, oldval, newval);
 }
 
 /**
  * atomic_inc() - Atomic incrememnt
  * @addr:	Address of the variable to increment
  *
- * Return the new value of addr->val.
+ * Return the new value of addr->counter.
  */
 static inline int
 atomic_inc(atomic_t *addr)
 {
-	return __sync_add_and_fetch(&addr->val, 1);
+	return __sync_add_and_fetch(&addr->counter, 1);
 }
 
 /**
  * atomic_dec() - Atomic decrement
  * @addr:	Address of the variable to decrement
  *
- * Return the new value of addr-val.
+ * Return the new value of addr-counter.
  */
 static inline int
 atomic_dec(atomic_t *addr)
 {
-	return __sync_sub_and_fetch(&addr->val, 1);
+	return __sync_sub_and_fetch(&addr->counter, 1);
 }
 
 /**
@@ -67,12 +66,12 @@ atomic_dec(atomic_t *addr)
  * @addr:	Address of the variable to set
  * @newval:	New value for the atomic_t
  *
- * Return the new value of addr->val.
+ * Return the new value of addr->counter.
  */
 static inline int
 atomic_set(atomic_t *addr, int newval)
 {
-	addr->val = newval;
+	WRITE_ONCE(addr->counter, newval);
 	return newval;
 }
 
@@ -80,12 +79,12 @@ atomic_set(atomic_t *addr, int newval)
  * atomic_read() - Atomic read
  * @addr:	Address of the variable to read
  *
- * Return the value of addr->val.
+ * Return the value of addr->counter.
  */
 static inline int
 atomic_read(atomic_t *addr)
 {
-	return addr->val;
+	return READ_ONCE(addr->counter);
 }
 
 #endif
-- 
2.34.1

[PATCH v2 4/5] selftests/futex: introduce the declaration of atomic_t from types.h

[Licay]

> Introduce the header files specifically prepared for test programs
> from the tools/include directory. And solve the problem that
> atomic_read and atomic_set may not be safe in a multi - threaded
> environment.
>
> Signed-off-by: Yuwen Chen <ywen.chen@foxmail.com>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202512112344.gsyPl2ag-lkp@intel.com/
> ---
>  .../selftests/futex/functional/Makefile       |  2 +-
>  .../testing/selftests/futex/include/atomic.h  | 25 +++++++++----------
>  2 files changed, 13 insertions(+), 14 deletions(-)
Reviewed-by: Licay <licayy@foxmail.com>

[PATCH v2 5/5] selftests/futex: fix the issue of abnormal test results caused by thread timing

[Yuwen Chen]

Fixes a race between parent and child threads in futex_requeue.

Similar to commit fbf4dec70277 ("selftests/futex: Order calls to
futex_lock_pi"), which fixed a flake in futex_lock_pi due to racing
between the parent and child threads.

The same issue can occur in the futex_requeue test, because it expects
waiterfn to make progress to futex_wait before the parent starts to
requeue. This is mitigated by the parent sleeping for WAKE_WAIT_US, but
it still fails occasionally. This can be reproduced by adding a sleep in
the waiterfn before futex_wait:

TAP version 13
1..2
not ok 1 futex_requeue simple returned: 0
not ok 2 futex_requeue simple returned: 0
not ok 3 futex_requeue many returned: 0
not ok 4 futex_requeue many returned: 0

This issue can be resolved by checking whether the child thread is in a
sleeping state. This is because when the child thread goes to sleep, it
indicates that it is waiting for the futex lock.

Fixes: 7cb5dd8e2c8c ("selftests: futex: Add futex compare requeue test")
Signed-off-by: Yuwen Chen <ywen.chen@foxmail.com>
Co-developed-by: Edward Liaw <edliaw@google.com>
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 .../futex/functional/futex_requeue.c          | 58 ++++++++++++++++---
 1 file changed, 51 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/futex/functional/futex_requeue.c b/tools/testing/selftests/futex/functional/futex_requeue.c
index 7a22458c7fc96..994295fac6972 100644
--- a/tools/testing/selftests/futex/functional/futex_requeue.c
+++ b/tools/testing/selftests/futex/functional/futex_requeue.c
@@ -7,6 +7,7 @@
 
 #include <pthread.h>
 #include <limits.h>
+#include <linux/compiler.h>
 
 #include "futextest.h"
 #include "../../kselftest_harness.h"
@@ -15,6 +16,7 @@
 #define WAKE_WAIT_US 10000
 
 volatile futex_t *f1;
+static pthread_barrier_t barrier;
 
 void *waiterfn(void *arg)
 {
@@ -23,28 +25,59 @@ void *waiterfn(void *arg)
 	to.tv_sec = 0;
 	to.tv_nsec = timeout_ns;
 
+	WRITE_ONCE(*((pid_t *)arg), gettid());
+	pthread_barrier_wait(&barrier);
+
 	if (futex_wait(f1, *f1, &to, 0))
 		printf("waiter failed errno %d\n", errno);
 
 	return NULL;
 }
 
+static int get_thread_state(pid_t pid)
+{
+	FILE *fp;
+	char buf[80], tag[80];
+	char val = 0;
+
+	snprintf(buf, sizeof(buf), "/proc/%d/status", pid);
+	fp = fopen(buf, "r");
+	if (!fp)
+		return -1;
+
+	while (fgets(buf, sizeof(buf), fp))
+		if (fscanf(fp, "%s %c\n", tag, &val) == 2 && !strcmp(tag, "State:"))
+			break;
+
+	fclose(fp);
+	return val;
+}
+
 TEST(requeue_single)
 {
 	volatile futex_t _f1 = 0;
 	volatile futex_t f2 = 0;
 	pthread_t waiter;
-	int res;
+	pid_t tids;
+	int res, state;
 
 	f1 = &_f1;
+	pthread_barrier_init(&barrier, NULL, 2);
 
 	/*
 	 * Requeue a waiter from f1 to f2, and wake f2.
 	 */
-	if (pthread_create(&waiter, NULL, waiterfn, NULL))
+	if (pthread_create(&waiter, NULL, waiterfn, &tids))
 		ksft_exit_fail_msg("pthread_create failed\n");
 
-	usleep(WAKE_WAIT_US);
+	pthread_barrier_wait(&barrier);
+	pthread_barrier_destroy(&barrier);
+	while ((state = get_thread_state(READ_ONCE(tids))) != 'S') {
+		usleep(WAKE_WAIT_US);
+
+		if (state < 0)
+			break;
+	}
 
 	ksft_print_dbg_msg("Requeuing 1 futex from f1 to f2\n");
 	res = futex_cmp_requeue(f1, 0, &f2, 0, 1, 0);
@@ -71,7 +104,8 @@ TEST(requeue_multiple)
 	volatile futex_t _f1 = 0;
 	volatile futex_t f2 = 0;
 	pthread_t waiter[10];
-	int res, i;
+	pid_t tids[10];
+	int res, i, state;
 
 	f1 = &_f1;
 
@@ -80,11 +114,21 @@ TEST(requeue_multiple)
 	 * At futex_wake, wake INT_MAX (should be exactly 7).
 	 */
 	for (i = 0; i < 10; i++) {
-		if (pthread_create(&waiter[i], NULL, waiterfn, NULL))
+		pthread_barrier_init(&barrier, NULL, 2);
+
+		if (pthread_create(&waiter[i], NULL, waiterfn, &tids[i]))
 			ksft_exit_fail_msg("pthread_create failed\n");
-	}
 
-	usleep(WAKE_WAIT_US);
+		pthread_barrier_wait(&barrier);
+		pthread_barrier_destroy(&barrier);
+
+		while ((state = get_thread_state(READ_ONCE(tids[i]))) != 'S') {
+			usleep(WAKE_WAIT_US);
+
+			if (state < 0)
+				break;
+		}
+	}
 
 	ksft_print_dbg_msg("Waking 3 futexes at f1 and requeuing 7 futexes from f1 to f2\n");
 	res = futex_cmp_requeue(f1, 0, &f2, 3, 7, 0);
-- 
2.34.1

[PATCH v2 5/5] selftests/futex: fix the issue of abnormal test results caused by thread timing

[Licay]

> Fixes a race between parent and child threads in futex_requeue.
>
> Similar to commit fbf4dec70277 ("selftests/futex: Order calls to
> futex_lock_pi"), which fixed a flake in futex_lock_pi due to racing
> between the parent and child threads.
>
> The same issue can occur in the futex_requeue test, because it expects
> waiterfn to make progress to futex_wait before the parent starts to
> requeue. This is mitigated by the parent sleeping for WAKE_WAIT_US, but
> it still fails occasionally. This can be reproduced by adding a sleep in
> the waiterfn before futex_wait:
>
> TAP version 13
> 1..2
> not ok 1 futex_requeue simple returned: 0
> not ok 2 futex_requeue simple returned: 0
> not ok 3 futex_requeue many returned: 0
> not ok 4 futex_requeue many returned: 0
>
> This issue can be resolved by checking whether the child thread is in a
> sleeping state. This is because when the child thread goes to sleep, it
> indicates that it is waiting for the futex lock.
>
> Fixes: 7cb5dd8e2c8c ("selftests: futex: Add futex compare requeue test")
> Signed-off-by: Yuwen Chen <ywen.chen@foxmail.com>
> Co-developed-by: Edward Liaw <edliaw@google.com>
> Signed-off-by: Edward Liaw <edliaw@google.com>
> ---
>  .../futex/functional/futex_requeue.c          | 58 ++++++++++++++++---
>  1 file changed, 51 insertions(+), 7 deletions(-)
Reviewed-by: Licay <licayy@foxmail.com>