[PATCH 0/5] futex: Random fixes after the private-hash series.

[PATCH 0/5] futex: Random fixes after the private-hash series.

[Sebastian Andrzej Siewior]

A few things were raised after the private-hash series has been merged.
Here are the fixes for it. Nothing serious but should be merged before
it hits ht merge window.

Sebastian Andrzej Siewior (5):
  selftests/futex: Use TAP output in futex_priv_hash
  selftests/futex: Use TAP output in futex_numa_mpol
  futex: Use RCU_INIT_POINTER() in futex_mm_init().
  tools headers: Synchronize prctl.h ABI header
  futex: Correct the kernedoc return value for futex_wait_setup().

 include/linux/futex.h                         |   9 +-
 kernel/futex/waitwake.c                       |   3 +-
 tools/include/uapi/linux/prctl.h              |   1 +
 .../futex/functional/futex_numa_mpol.c        |  65 ++++---
 .../futex/functional/futex_priv_hash.c        | 168 ++++++++----------
 5 files changed, 108 insertions(+), 138 deletions(-)

Sebastian

[PATCH 1/5] selftests/futex: Use TAP output in futex_priv_hash

[Sebastian Andrzej Siewior]

Use TAP output for easier automated testing.

Suggested-by: André Almeida <andrealmeid@igalia.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 .../futex/functional/futex_priv_hash.c        | 150 ++++++++----------
 1 file changed, 63 insertions(+), 87 deletions(-)

diff --git a/tools/testing/selftests/futex/functional/futex_priv_hash.c b/tools/testing/selftests/futex/functional/futex_priv_hash.c
index 4d37650baa192..72a621d9313f3 100644
--- a/tools/testing/selftests/futex/functional/futex_priv_hash.c
+++ b/tools/testing/selftests/futex/functional/futex_priv_hash.c
@@ -51,15 +51,16 @@ static void futex_hash_slots_set_verify(int slots)
 
 	ret = futex_hash_slots_set(slots, 0);
 	if (ret != 0) {
-		error("Failed to set slots to %d\n", errno, slots);
-		exit(1);
+		ksft_test_result_fail("Failed to set slots to %d: %m\n", slots);
+		ksft_finished();
 	}
 	ret = futex_hash_slots_get();
 	if (ret != slots) {
-		error("Set %d slots but PR_FUTEX_HASH_GET_SLOTS returns: %d\n",
-		       errno, slots, ret);
-		exit(1);
+		ksft_test_result_fail("Set %d slots but PR_FUTEX_HASH_GET_SLOTS returns: %d, %m\n",
+		       slots, ret);
+		ksft_finished();
 	}
+	ksft_test_result_pass("SET and GET slots %d passed\n", slots);
 }
 
 static void futex_hash_slots_set_must_fail(int slots, int immutable)
@@ -67,12 +68,8 @@ static void futex_hash_slots_set_must_fail(int slots, int immutable)
 	int ret;
 
 	ret = futex_hash_slots_set(slots, immutable);
-	if (ret < 0)
-		return;
-
-	fail("futex_hash_slots_set(%d, %d) expected to fail but succeeded.\n",
-	       slots, immutable);
-	exit(1);
+	ksft_test_result(ret < 0, "futex_hash_slots_set(%d, %d)\n",
+			 slots, immutable);
 }
 
 static void *thread_return_fn(void *arg)
@@ -97,10 +94,8 @@ static void create_max_threads(void *(*thread_fn)(void *))
 
 	for (i = 0; i < MAX_THREADS; i++) {
 		ret = pthread_create(&threads[i], NULL, thread_fn, NULL);
-		if (ret) {
-			error("pthread_create failed\n", errno);
-			exit(1);
-		}
+		if (ret)
+			ksft_exit_fail_msg("pthread_create failed: %m\n");
 	}
 }
 
@@ -110,10 +105,8 @@ static void join_max_threads(void)
 
 	for (i = 0; i < MAX_THREADS; i++) {
 		ret = pthread_join(threads[i], NULL);
-		if (ret) {
-			error("pthread_join failed for thread %d\n", errno, i);
-			exit(1);
-		}
+		if (ret)
+			ksft_exit_fail_msg("pthread_join failed for thread %d\n", i);
 	}
 }
 
@@ -127,6 +120,9 @@ static void usage(char *prog)
 	       VQUIET, VCRITICAL, VINFO);
 }
 
+static const char *test_msg_auto_create = "Automatic hash bucket init on thread creation.\n";
+static const char *test_msg_auto_inc = "Automatic increase with more than 16 CPUs\n";
+
 int main(int argc, char *argv[])
 {
 	int futex_slots1, futex_slotsn, online_cpus;
@@ -156,56 +152,50 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	ksft_print_header();
+	ksft_set_plan(22);
 
 	ret = pthread_mutexattr_init(&mutex_attr_pi);
 	ret |= pthread_mutexattr_setprotocol(&mutex_attr_pi, PTHREAD_PRIO_INHERIT);
 	ret |= pthread_mutex_init(&global_lock, &mutex_attr_pi);
 	if (ret != 0) {
-		fail("Failed to initialize pthread mutex.\n");
-		return 1;
+		ksft_exit_fail_msg("Failed to initialize pthread mutex.\n");
 	}
-
 	/* First thread, expect to be 0, not yet initialized */
 	ret = futex_hash_slots_get();
-	if (ret != 0) {
-		error("futex_hash_slots_get() failed: %d\n", errno, ret);
-		return 1;
-	}
-	ret = futex_hash_immutable_get();
-	if (ret != 0) {
-		error("futex_hash_immutable_get() failed: %d\n", errno, ret);
-		return 1;
-	}
+	if (ret != 0)
+		ksft_exit_fail_msg("futex_hash_slots_get() failed: %d, %m\n", ret);
 
+	ret = futex_hash_immutable_get();
+	if (ret != 0)
+		ksft_exit_fail_msg("futex_hash_immutable_get() failed: %d, %m\n", ret);
+
+	ksft_test_result_pass("Basic get slots and immutable status.\n");
 	ret = pthread_create(&threads[0], NULL, thread_return_fn, NULL);
-	if (ret != 0) {
-		error("pthread_create() failed: %d\n", errno, ret);
-		return 1;
-	}
+	if (ret != 0)
+		ksft_exit_fail_msg("pthread_create() failed: %d, %m\n", ret);
+
 	ret = pthread_join(threads[0], NULL);
-	if (ret != 0) {
-		error("pthread_join() failed: %d\n", errno, ret);
-		return 1;
-	}
+	if (ret != 0)
+		ksft_exit_fail_msg("pthread_join() failed: %d, %m\n", ret);
+
 	/* First thread, has to initialiaze private hash */
 	futex_slots1 = futex_hash_slots_get();
 	if (futex_slots1 <= 0) {
-		fail("Expected > 0 hash buckets, got: %d\n", futex_slots1);
-		return 1;
+		ksft_print_msg("Current hash buckets: %d\n", futex_slots1);
+		ksft_exit_fail_msg(test_msg_auto_create);
 	}
 
+	ksft_test_result_pass(test_msg_auto_create);
+
 	online_cpus = sysconf(_SC_NPROCESSORS_ONLN);
 	ret = pthread_barrier_init(&barrier_main, NULL, MAX_THREADS + 1);
-	if (ret != 0) {
-		error("pthread_barrier_init failed.\n", errno);
-		return 1;
-	}
+	if (ret != 0)
+		ksft_exit_fail_msg("pthread_barrier_init failed: %m.\n");
 
 	ret = pthread_mutex_lock(&global_lock);
-	if (ret != 0) {
-		error("pthread_mutex_lock failed.\n", errno);
-		return 1;
-	}
+	if (ret != 0)
+		ksft_exit_fail_msg("pthread_mutex_lock failed: %m.\n");
 
 	counter = 0;
 	create_max_threads(thread_lock_fn);
@@ -215,14 +205,17 @@ int main(int argc, char *argv[])
 	 * The current default size of hash buckets is 16. The auto increase
 	 * works only if more than 16 CPUs are available.
 	 */
+	ksft_print_msg("Online CPUs: %d\n", online_cpus);
 	if (online_cpus > 16) {
 		futex_slotsn = futex_hash_slots_get();
 		if (futex_slotsn < 0 || futex_slots1 == futex_slotsn) {
-			fail("Expected increase of hash buckets but got: %d -> %d\n",
-			      futex_slots1, futex_slotsn);
-			info("Online CPUs: %d\n", online_cpus);
-			return 1;
+			ksft_print_msg("Expected increase of hash buckets but got: %d -> %d\n",
+				       futex_slots1, futex_slotsn);
+			ksft_exit_fail_msg(test_msg_auto_inc);
 		}
+		ksft_test_result_pass(test_msg_auto_inc);
+	} else {
+		ksft_test_result_skip(test_msg_auto_inc);
 	}
 	ret = pthread_mutex_unlock(&global_lock);
 
@@ -234,17 +227,12 @@ int main(int argc, char *argv[])
 	futex_hash_slots_set_verify(16);
 
 	ret = futex_hash_slots_set(15, 0);
-	if (ret >= 0) {
-		fail("Expected to fail with 15 slots but succeeded: %d.\n", ret);
-		return 1;
-	}
+	ksft_test_result(ret < 0, "Use 15 slots\n");
+
 	futex_hash_slots_set_verify(2);
 	join_max_threads();
-	if (counter != MAX_THREADS) {
-		fail("Expected thread counter at %d but is %d\n",
-		       MAX_THREADS, counter);
-		return 1;
-	}
+	ksft_test_result(counter == MAX_THREADS, "Created of waited for %d of %d threads\n",
+			 counter, MAX_THREADS);
 	counter = 0;
 	/* Once the user set something, auto reisze must be disabled */
 	ret = pthread_barrier_init(&barrier_main, NULL, MAX_THREADS);
@@ -253,10 +241,8 @@ int main(int argc, char *argv[])
 	join_max_threads();
 
 	ret = futex_hash_slots_get();
-	if (ret != 2) {
-		printf("Expected 2 slots, no auto-resize, got %d\n", ret);
-		return 1;
-	}
+	ksft_test_result(ret == 2, "No more auto-resize after manaul setting, got %d\n",
+			 ret);
 
 	futex_hash_slots_set_must_fail(1 << 29, 0);
 
@@ -266,17 +252,13 @@ int main(int argc, char *argv[])
 	 */
 	if (use_global_hash) {
 		ret = futex_hash_slots_set(0, 0);
-		if (ret != 0) {
-			printf("Can't request global hash: %m\n");
-			return 1;
-		}
+		ksft_test_result(ret == 0, "Global hash request\n");
 	} else {
 		ret = futex_hash_slots_set(4, 1);
-		if (ret != 0) {
-			printf("Immutable resize to 4 failed: %m\n");
-			return 1;
-		}
+		ksft_test_result(ret == 0, "Immutable resize to 4\n");
 	}
+	if (ret != 0)
+		goto out;
 
 	futex_hash_slots_set_must_fail(4, 0);
 	futex_hash_slots_set_must_fail(4, 1);
@@ -287,7 +269,7 @@ int main(int argc, char *argv[])
 
 	ret = pthread_barrier_init(&barrier_main, NULL, MAX_THREADS);
 	if (ret != 0) {
-		error("pthread_barrier_init failed.\n", errno);
+		ksft_exit_fail_msg("pthread_barrier_init failed: %m\n");
 		return 1;
 	}
 	create_max_threads(thread_lock_fn);
@@ -295,21 +277,15 @@ int main(int argc, char *argv[])
 
 	ret = futex_hash_slots_get();
 	if (use_global_hash) {
-		if (ret != 0) {
-			error("Expected global hash, got %d\n", errno, ret);
-			return 1;
-		}
+		ksft_test_result(ret == 0, "Continue to use global hash\n");
 	} else {
-		if (ret != 4) {
-			error("Expected 4 slots, no auto-resize, got %d\n", errno, ret);
-			return 1;
-		}
+		ksft_test_result(ret == 4, "Continue to use the 4 hash buckets\n");
 	}
 
 	ret = futex_hash_immutable_get();
-	if (ret != 1) {
-		fail("Expected immutable private hash, got %d\n", ret);
-		return 1;
-	}
+	ksft_test_result(ret == 1, "Hash reports to be immutable\n");
+
+out:
+	ksft_finished();
 	return 0;
 }
-- 
2.49.0

Re: [PATCH 1/5] selftests/futex: Use TAP output in futex_priv_hash

[André Almeida]

Em 16/05/2025 13:03, Sebastian Andrzej Siewior escreveu:
> Use TAP output for easier automated testing.
> 
> Suggested-by: André Almeida <andrealmeid@igalia.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Reviewed-by: André Almeida <andrealmeid@igalia.com>

[PATCH 2/5] selftests/futex: Use TAP output in futex_numa_mpol

[Sebastian Andrzej Siewior]

Use TAP output for easier automated testing.

Suggested-by: André Almeida <andrealmeid@igalia.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 .../futex/functional/futex_numa_mpol.c        | 65 +++++++++----------
 1 file changed, 32 insertions(+), 33 deletions(-)

diff --git a/tools/testing/selftests/futex/functional/futex_numa_mpol.c b/tools/testing/selftests/futex/functional/futex_numa_mpol.c
index dd70532f293ec..d18949ea915aa 100644
--- a/tools/testing/selftests/futex/functional/futex_numa_mpol.c
+++ b/tools/testing/selftests/futex/functional/futex_numa_mpol.c
@@ -61,10 +61,8 @@ static void create_max_threads(void *futex_ptr)
 		thread_args[i].flags = FUTEX2_SIZE_U32 | FUTEX_PRIVATE_FLAG | FUTEX2_NUMA;
 		thread_args[i].result = 0;
 		ret = pthread_create(&threads[i], NULL, thread_lock_fn, &thread_args[i]);
-		if (ret) {
-			error("pthread_create failed\n", errno);
-			exit(1);
-		}
+		if (ret)
+			ksft_exit_fail_msg("pthread_create failed\n");
 	}
 }
 
@@ -74,10 +72,8 @@ static void join_max_threads(void)
 
 	for (i = 0; i < MAX_THREADS; i++) {
 		ret = pthread_join(threads[i], NULL);
-		if (ret) {
-			error("pthread_join failed for thread %d\n", errno, i);
-			exit(1);
-		}
+		if (ret)
+			ksft_exit_fail_msg("pthread_join failed for thread %d\n", i);
 	}
 }
 
@@ -95,12 +91,12 @@ static void __test_futex(void *futex_ptr, int must_fail, unsigned int futex_flag
 		if (must_fail) {
 			if (ret < 0)
 				break;
-			fail("Should fail, but didn't\n");
-			exit(1);
+			ksft_exit_fail_msg("futex2_wake(%d, 0x%x) should fail, but didn't\n",
+					   to_wake, futex_flags);
 		}
 		if (ret < 0) {
-			error("Failed futex2_wake(%d)\n", errno, to_wake);
-			exit(1);
+			ksft_exit_fail_msg("Failed futex2_wake(%d, 0x%x): %m\n",
+					   to_wake, futex_flags);
 		}
 		if (!ret)
 			usleep(50);
@@ -111,16 +107,17 @@ static void __test_futex(void *futex_ptr, int must_fail, unsigned int futex_flag
 
 	for (i = 0; i < MAX_THREADS; i++) {
 		if (must_fail && thread_args[i].result != -1) {
-			fail("Thread %d should fail but succeeded (%d)\n", i, thread_args[i].result);
+			ksft_print_msg("Thread %d should fail but succeeded (%d)\n",
+				       i, thread_args[i].result);
 			need_exit = 1;
 		}
 		if (!must_fail && thread_args[i].result != 0) {
-			fail("Thread %d failed (%d)\n", i, thread_args[i].result);
+			ksft_print_msg("Thread %d failed (%d)\n", i, thread_args[i].result);
 			need_exit = 1;
 		}
 	}
 	if (need_exit)
-		exit(1);
+		ksft_exit_fail_msg("Aborting due to earlier errors.\n");
 }
 
 static void test_futex(void *futex_ptr, int must_fail)
@@ -167,41 +164,41 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	ksft_print_header();
+	ksft_set_plan(1);
+
 	mem_size = sysconf(_SC_PAGE_SIZE);
 	futex_ptr = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
-	if (futex_ptr == MAP_FAILED) {
-		error("mmap() for %d bytes failed\n", errno, mem_size);
-		return 1;
-	}
+	if (futex_ptr == MAP_FAILED)
+		ksft_exit_fail_msg("mmap() for %d bytes failed\n", mem_size);
+
 	futex_numa = futex_ptr;
 
-	info("Regular test\n");
+	ksft_print_msg("Regular test\n");
 	futex_numa->futex = 0;
 	futex_numa->numa = FUTEX_NO_NODE;
 	test_futex(futex_ptr, 0);
 
-	if (futex_numa->numa == FUTEX_NO_NODE) {
-		fail("NUMA node is left unitiliazed\n");
-		return 1;
-	}
+	if (futex_numa->numa == FUTEX_NO_NODE)
+		ksft_exit_fail_msg("NUMA node is left unitiliazed\n");
 
-	info("Memory too small\n");
+	ksft_print_msg("Memory too small\n");
 	test_futex(futex_ptr + mem_size - 4, 1);
 
-	info("Memory out of range\n");
+	ksft_print_msg("Memory out of range\n");
 	test_futex(futex_ptr + mem_size, 1);
 
 	futex_numa->numa = FUTEX_NO_NODE;
 	mprotect(futex_ptr, mem_size, PROT_READ);
-	info("Memory, RO\n");
+	ksft_print_msg("Memory, RO\n");
 	test_futex(futex_ptr, 1);
 
 	mprotect(futex_ptr, mem_size, PROT_NONE);
-	info("Memory, no access\n");
+	ksft_print_msg("Memory, no access\n");
 	test_futex(futex_ptr, 1);
 
 	mprotect(futex_ptr, mem_size, PROT_READ | PROT_WRITE);
-	info("Memory back to RW\n");
+	ksft_print_msg("Memory back to RW\n");
 	test_futex(futex_ptr, 0);
 
 	/* MPOL test. Does not work as expected */
@@ -213,20 +210,22 @@ int main(int argc, char *argv[])
 		ret = mbind(futex_ptr, mem_size, MPOL_BIND, &nodemask,
 			    sizeof(nodemask) * 8, 0);
 		if (ret == 0) {
-			info("Node %d test\n", i);
+			ksft_print_msg("Node %d test\n", i);
 			futex_numa->futex = 0;
 			futex_numa->numa = FUTEX_NO_NODE;
 
 			ret = futex2_wake(futex_ptr, 0, FUTEX2_SIZE_U32 | FUTEX_PRIVATE_FLAG | FUTEX2_NUMA | FUTEX2_MPOL);
 			if (ret < 0)
-				error("Failed to wake 0 with MPOL.\n", errno);
+				ksft_test_result_fail("Failed to wake 0 with MPOL: %m\n");
 			if (0)
 				test_futex_mpol(futex_numa, 0);
 			if (futex_numa->numa != i) {
-				fail("Returned NUMA node is %d expected %d\n",
-				     futex_numa->numa, i);
+				ksft_test_result_fail("Returned NUMA node is %d expected %d\n",
+						      futex_numa->numa, i);
 			}
 		}
 	}
+	ksft_test_result_pass("NUMA MPOL tests passed\n");
+	ksft_finished();
 	return 0;
 }
-- 
2.49.0

Re: [PATCH 2/5] selftests/futex: Use TAP output in futex_numa_mpol

[André Almeida]

Em 16/05/2025 13:03, Sebastian Andrzej Siewior escreveu:
> Use TAP output for easier automated testing.
> 
> Suggested-by: André Almeida <andrealmeid@igalia.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---

Reviewed-by: André Almeida <andrealmeid@igalia.com>

[PATCH 3/5] futex: Use RCU_INIT_POINTER() in futex_mm_init().

[Sebastian Andrzej Siewior]

There is no need for an explicit NULL pointer initialisation plus a
comment why it is okay. RCU_INIT_POINTER() can be used for NULL
initialisations and it is documented.

This has been build tested with gcc version 9.3.0 (Debian 9.3.0-22) on a
x86-64 defconfig.

Fixes: 094ac8cff7858 ("futex: Relax the rcu_assign_pointer() assignment of mm->futex_phash in futex_mm_init()")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 include/linux/futex.h | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/include/linux/futex.h b/include/linux/futex.h
index 168ffd5996b48..005b040c4791b 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -88,14 +88,7 @@ void futex_hash_free(struct mm_struct *mm);
 
 static inline void futex_mm_init(struct mm_struct *mm)
 {
-	/*
-	 * No need for rcu_assign_pointer() here, as we can rely on
-	 * tasklist_lock write-ordering in copy_process(), before
-	 * the task's MM becomes visible and the ->futex_phash
-	 * becomes externally observable:
-	 */
-	mm->futex_phash = NULL;
-
+	RCU_INIT_POINTER(mm->futex_phash, NULL);
 	mutex_init(&mm->futex_hash_lock);
 }
 
-- 
2.49.0

[PATCH 4/5] tools headers: Synchronize prctl.h ABI header

[Sebastian Andrzej Siewior]

The prctl.h ABI header was slightly updated during the development of
the interface. In particular the "immutable" parameter became a bit in
the option argument.

Synchronize prctl.h ABI header again and make use of the definition in
the testsuite.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 tools/include/uapi/linux/prctl.h               |  1 +
 .../futex/functional/futex_priv_hash.c         | 18 +++++++++---------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/tools/include/uapi/linux/prctl.h b/tools/include/uapi/linux/prctl.h
index 21f30b3ded74b..43dec6eed559a 100644
--- a/tools/include/uapi/linux/prctl.h
+++ b/tools/include/uapi/linux/prctl.h
@@ -367,6 +367,7 @@ struct prctl_mm_map {
 /* FUTEX hash management */
 #define PR_FUTEX_HASH			78
 # define PR_FUTEX_HASH_SET_SLOTS	1
+# define FH_FLAG_IMMUTABLE		(1ULL << 0)
 # define PR_FUTEX_HASH_GET_SLOTS	2
 # define PR_FUTEX_HASH_GET_IMMUTABLE	3
 
diff --git a/tools/testing/selftests/futex/functional/futex_priv_hash.c b/tools/testing/selftests/futex/functional/futex_priv_hash.c
index 72a621d9313f3..32abd9acdf186 100644
--- a/tools/testing/selftests/futex/functional/futex_priv_hash.c
+++ b/tools/testing/selftests/futex/functional/futex_priv_hash.c
@@ -30,9 +30,9 @@ static int counter;
 # define PR_FUTEX_HASH_GET_IMMUTABLE	3
 #endif
 
-static int futex_hash_slots_set(unsigned int slots, int immutable)
+static int futex_hash_slots_set(unsigned int slots, int flags)
 {
-	return prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_SET_SLOTS, slots, immutable);
+	return prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_SET_SLOTS, slots, flags);
 }
 
 static int futex_hash_slots_get(void)
@@ -63,11 +63,11 @@ static void futex_hash_slots_set_verify(int slots)
 	ksft_test_result_pass("SET and GET slots %d passed\n", slots);
 }
 
-static void futex_hash_slots_set_must_fail(int slots, int immutable)
+static void futex_hash_slots_set_must_fail(int slots, int flags)
 {
 	int ret;
 
-	ret = futex_hash_slots_set(slots, immutable);
+	ret = futex_hash_slots_set(slots, flags);
 	ksft_test_result(ret < 0, "futex_hash_slots_set(%d, %d)\n",
 			 slots, immutable);
 }
@@ -254,18 +254,18 @@ int main(int argc, char *argv[])
 		ret = futex_hash_slots_set(0, 0);
 		ksft_test_result(ret == 0, "Global hash request\n");
 	} else {
-		ret = futex_hash_slots_set(4, 1);
+		ret = futex_hash_slots_set(4, FH_FLAG_IMMUTABLE);
 		ksft_test_result(ret == 0, "Immutable resize to 4\n");
 	}
 	if (ret != 0)
 		goto out;
 
 	futex_hash_slots_set_must_fail(4, 0);
-	futex_hash_slots_set_must_fail(4, 1);
+	futex_hash_slots_set_must_fail(4, FH_FLAG_IMMUTABLE);
 	futex_hash_slots_set_must_fail(8, 0);
-	futex_hash_slots_set_must_fail(8, 1);
-	futex_hash_slots_set_must_fail(0, 1);
-	futex_hash_slots_set_must_fail(6, 1);
+	futex_hash_slots_set_must_fail(8, FH_FLAG_IMMUTABLE);
+	futex_hash_slots_set_must_fail(0, FH_FLAG_IMMUTABLE);
+	futex_hash_slots_set_must_fail(6, FH_FLAG_IMMUTABLE);
 
 	ret = pthread_barrier_init(&barrier_main, NULL, MAX_THREADS);
 	if (ret != 0) {
-- 
2.49.0

Re: [PATCH 4/5] tools headers: Synchronize prctl.h ABI header

[André Almeida]

Hi Sebastian,

Thank you for incorporating my feedback :)

Em 16/05/2025 13:03, Sebastian Andrzej Siewior escreveu:
> The prctl.h ABI header was slightly updated during the development of
> the interface. In particular the "immutable" parameter became a bit in
> the option argument.
> 
> Synchronize prctl.h ABI header again and make use of the definition in
> the testsuite.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>   tools/include/uapi/linux/prctl.h               |  1 +
>   .../futex/functional/futex_priv_hash.c         | 18 +++++++++---------
>   2 files changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/include/uapi/linux/prctl.h b/tools/include/uapi/linux/prctl.h
> index 21f30b3ded74b..43dec6eed559a 100644
> --- a/tools/include/uapi/linux/prctl.h
> +++ b/tools/include/uapi/linux/prctl.h
> @@ -367,6 +367,7 @@ struct prctl_mm_map {
>   /* FUTEX hash management */
>   #define PR_FUTEX_HASH			78
>   # define PR_FUTEX_HASH_SET_SLOTS	1
> +# define FH_FLAG_IMMUTABLE		(1ULL << 0)
>   # define PR_FUTEX_HASH_GET_SLOTS	2
>   # define PR_FUTEX_HASH_GET_IMMUTABLE	3
>   
> diff --git a/tools/testing/selftests/futex/functional/futex_priv_hash.c b/tools/testing/selftests/futex/functional/futex_priv_hash.c
> index 72a621d9313f3..32abd9acdf186 100644
> --- a/tools/testing/selftests/futex/functional/futex_priv_hash.c
> +++ b/tools/testing/selftests/futex/functional/futex_priv_hash.c
> @@ -30,9 +30,9 @@ static int counter;
>   # define PR_FUTEX_HASH_GET_IMMUTABLE	3
>   #endif
>   
> -static int futex_hash_slots_set(unsigned int slots, int immutable)
> +static int futex_hash_slots_set(unsigned int slots, int flags)
>   {
> -	return prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_SET_SLOTS, slots, immutable);
> +	return prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_SET_SLOTS, slots, flags);
>   }
>   
>   static int futex_hash_slots_get(void)
> @@ -63,11 +63,11 @@ static void futex_hash_slots_set_verify(int slots)
>   	ksft_test_result_pass("SET and GET slots %d passed\n", slots);
>   }
>   
> -static void futex_hash_slots_set_must_fail(int slots, int immutable)
> +static void futex_hash_slots_set_must_fail(int slots, int flags)
>   {
>   	int ret;
>   
> -	ret = futex_hash_slots_set(slots, immutable);
> +	ret = futex_hash_slots_set(slots, flags);
>   	ksft_test_result(ret < 0, "futex_hash_slots_set(%d, %d)\n",
>   			 slots, immutable);

s/immutable/flags

>   }
> @@ -254,18 +254,18 @@ int main(int argc, char *argv[])
>   		ret = futex_hash_slots_set(0, 0);
>   		ksft_test_result(ret == 0, "Global hash request\n");
>   	} else {
> -		ret = futex_hash_slots_set(4, 1);
> +		ret = futex_hash_slots_set(4, FH_FLAG_IMMUTABLE);

This breaks the compilation for me.

So `#include <linux/prctl.h>` is not working for me, it's not using the 
local copy at tools/include/uapi/linux/prctl.h

Re: [PATCH 4/5] tools headers: Synchronize prctl.h ABI header

[André Almeida]

Em 16/05/2025 17:03, André Almeida escreveu:
> Hi Sebastian,
> 
> Thank you for incorporating my feedback :)
> 
> Em 16/05/2025 13:03, Sebastian Andrzej Siewior escreveu:
>> The prctl.h ABI header was slightly updated during the development of
>> the interface. In particular the "immutable" parameter became a bit in
>> the option argument.
>>
>> Synchronize prctl.h ABI header again and make use of the definition in
>> the testsuite.
>>
>> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>> ---
>>   tools/include/uapi/linux/prctl.h               |  1 +
>>   .../futex/functional/futex_priv_hash.c         | 18 +++++++++---------
>>   2 files changed, 10 insertions(+), 9 deletions(-)
>>
>> diff --git a/tools/include/uapi/linux/prctl.h b/tools/include/uapi/ 
>> linux/prctl.h
>> index 21f30b3ded74b..43dec6eed559a 100644
>> --- a/tools/include/uapi/linux/prctl.h
>> +++ b/tools/include/uapi/linux/prctl.h
>> @@ -367,6 +367,7 @@ struct prctl_mm_map {
>>   /* FUTEX hash management */
>>   #define PR_FUTEX_HASH            78
>>   # define PR_FUTEX_HASH_SET_SLOTS    1
>> +# define FH_FLAG_IMMUTABLE        (1ULL << 0)
>>   # define PR_FUTEX_HASH_GET_SLOTS    2
>>   # define PR_FUTEX_HASH_GET_IMMUTABLE    3
>> diff --git a/tools/testing/selftests/futex/functional/ 
>> futex_priv_hash.c b/tools/testing/selftests/futex/functional/ 
>> futex_priv_hash.c
>> index 72a621d9313f3..32abd9acdf186 100644
>> --- a/tools/testing/selftests/futex/functional/futex_priv_hash.c
>> +++ b/tools/testing/selftests/futex/functional/futex_priv_hash.c
>> @@ -30,9 +30,9 @@ static int counter;
>>   # define PR_FUTEX_HASH_GET_IMMUTABLE    3
>>   #endif
>> -static int futex_hash_slots_set(unsigned int slots, int immutable)
>> +static int futex_hash_slots_set(unsigned int slots, int flags)
>>   {
>> -    return prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_SET_SLOTS, slots, 
>> immutable);
>> +    return prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_SET_SLOTS, slots, flags);
>>   }
>>   static int futex_hash_slots_get(void)
>> @@ -63,11 +63,11 @@ static void futex_hash_slots_set_verify(int slots)
>>       ksft_test_result_pass("SET and GET slots %d passed\n", slots);
>>   }
>> -static void futex_hash_slots_set_must_fail(int slots, int immutable)
>> +static void futex_hash_slots_set_must_fail(int slots, int flags)
>>   {
>>       int ret;
>> -    ret = futex_hash_slots_set(slots, immutable);
>> +    ret = futex_hash_slots_set(slots, flags);
>>       ksft_test_result(ret < 0, "futex_hash_slots_set(%d, %d)\n",
>>                slots, immutable);
> 
> s/immutable/flags
> 
>>   }
>> @@ -254,18 +254,18 @@ int main(int argc, char *argv[])
>>           ret = futex_hash_slots_set(0, 0);
>>           ksft_test_result(ret == 0, "Global hash request\n");
>>       } else {
>> -        ret = futex_hash_slots_set(4, 1);
>> +        ret = futex_hash_slots_set(4, FH_FLAG_IMMUTABLE);
> 
> This breaks the compilation for me.
> 
> So `#include <linux/prctl.h>` is not working for me, it's not using the 
> local copy at tools/include/uapi/linux/prctl.h

Oh, nevermind, I found the issue:

--- a/tools/testing/selftests/futex/functional/futex_priv_hash.c
+++ b/tools/testing/selftests/futex/functional/futex_priv_hash.c
@@ -26,6 +26,7 @@ static int counter;
  #ifndef PR_FUTEX_HASH
  #define PR_FUTEX_HASH                  78
  # define PR_FUTEX_HASH_SET_SLOTS       1
+# define FH_FLAG_IMMUTABLE                (1ULL << 0)
  # define PR_FUTEX_HASH_GET_SLOTS       2
  # define PR_FUTEX_HASH_GET_IMMUTABLE   3
  #endif

Re: [PATCH 4/5] tools headers: Synchronize prctl.h ABI header

[Sebastian Andrzej Siewior]

On 2025-05-16 17:06:48 [-0300], André Almeida wrote:
> > > @@ -254,18 +254,18 @@ int main(int argc, char *argv[])
> > >           ret = futex_hash_slots_set(0, 0);
> > >           ksft_test_result(ret == 0, "Global hash request\n");
> > >       } else {
> > > -        ret = futex_hash_slots_set(4, 1);
> > > +        ret = futex_hash_slots_set(4, FH_FLAG_IMMUTABLE);
> > 
> > This breaks the compilation for me.
> > 
> > So `#include <linux/prctl.h>` is not working for me, it's not using the
> > local copy at tools/include/uapi/linux/prctl.h
> 
> Oh, nevermind, I found the issue:

Yeah, I am not sure what I did. I made here a copy, the copied header is
only used for perf. Anyway, I added the define as I did for the other
members and did the rename.

Sebastian

Re: [PATCH 4/5] tools headers: Synchronize prctl.h ABI header

[André Almeida]

Em 16/05/2025 13:03, Sebastian Andrzej Siewior escreveu:
> The prctl.h ABI header was slightly updated during the development of
> the interface. In particular the "immutable" parameter became a bit in
> the option argument.
> 
> Synchronize prctl.h ABI header again and make use of the definition in
> the testsuite.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

After fixing the s/immutable/flags and FH_FLAG_IMMUTABLE issues:

Reviewed-by: André Almeida <andrealmeid@igalia.com>

[PATCH 5/5] futex: Correct the kernedoc return value for futex_wait_setup()

[Sebastian Andrzej Siewior]

The kerneldoc for futex_wait_setup() states it can return "0" or "<1".
This isn't true because the error case is "<0" not less than 1.

Document that <0 is returned on error. Drop the possible return values
and state possible reasons.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/futex/waitwake.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c
index b3738fbe83c62..e2bbe5509ec27 100644
--- a/kernel/futex/waitwake.c
+++ b/kernel/futex/waitwake.c
@@ -585,7 +585,8 @@ int futex_wait_multiple(struct futex_vector *vs, unsigned int count,
  *
  * Return:
  *  -  0 - uaddr contains val and hb has been locked;
- *  - <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked
+ *  - <0 - On error and the hb is unlocked. A possible reason: the uaddr can not
+ *	   be read, does not contain the expected value or is not properly aligned.
  */
 int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
 		     struct futex_q *q, union futex_key *key2,
-- 
2.49.0

Re: [PATCH 5/5] futex: Correct the kernedoc return value for futex_wait_setup()

[André Almeida]

Em 16/05/2025 13:03, Sebastian Andrzej Siewior escreveu:
> The kerneldoc for futex_wait_setup() states it can return "0" or "<1".
> This isn't true because the error case is "<0" not less than 1.
> 
> Document that <0 is returned on error. Drop the possible return values
> and state possible reasons.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---

Reviewed-by: André Almeida <andrealmeid@igalia.com>