[PATCH v2 4/5] tools headers: Synchronize prctl.h ABI header

From: Sebastian Andrzej Siewior
Date: Sat May 17 2025 - 11:15:34 EST


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 and "perf bench futex".

Reviewed-by: André Almeida <andrealmeid@xxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
tools/include/uapi/linux/prctl.h | 1 +
tools/perf/bench/futex.c | 4 +++-
.../futex/functional/futex_priv_hash.c | 21 ++++++++++---------
3 files changed, 15 insertions(+), 11 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/perf/bench/futex.c b/tools/perf/bench/futex.c
index 02ae6c52ba881..26382e4d8d4ce 100644
--- a/tools/perf/bench/futex.c
+++ b/tools/perf/bench/futex.c
@@ -9,12 +9,14 @@

void futex_set_nbuckets_param(struct bench_futex_parameters *params)
{
+ unsigned long flags;
int ret;

if (params->nbuckets < 0)
return;

- ret = prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_SET_SLOTS, params->nbuckets, params->buckets_immutable);
+ flags = params->buckets_immutable ? FH_FLAG_IMMUTABLE : 0;
+ ret = prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_SET_SLOTS, params->nbuckets, flags);
if (ret) {
printf("Requesting %d hash buckets failed: %d/%m\n",
params->nbuckets, ret);
diff --git a/tools/testing/selftests/futex/functional/futex_priv_hash.c b/tools/testing/selftests/futex/functional/futex_priv_hash.c
index 72a621d9313f3..2dca18fefedcd 100644
--- a/tools/testing/selftests/futex/functional/futex_priv_hash.c
+++ b/tools/testing/selftests/futex/functional/futex_priv_hash.c
@@ -26,13 +26,14 @@ 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

-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)
@@ -63,13 +64,13 @@ 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);
+ slots, flags);
}

static void *thread_return_fn(void *arg)
@@ -254,18 +255,18 @@ 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