Re: [PATCH v2 1/1] selftests/futex: Check for shmget support at runtime

On Thu, Aug 07, 2025 at 08:00:42PM +0800, Wake Liu wrote:

The futex tests `futex_wait.c` and `futex_waitv.c` rely on the `shmget()` syscall, which may not be available if the kernel is built without System V IPC support (CONFIG_SYSVIPC=n). This can lead to test failures on such systems.

This patch modifies the tests to check for `shmget()` support at runtime by calling it and checking for an `ENOSYS` error. If `shmget()` is not supported, the tests are skipped with a clear message, improving the user experience and preventing false negatives.

This approach is more robust than relying on compile-time checks and ensures that the tests run only when the required kernel features are present.

Signed-off-by: Wake Liu wakel@google.com

.../selftests/futex/functional/futex_wait.c | 49 +++++++------ .../selftests/futex/functional/futex_waitv.c | 73 ++++++++++++------- 2 files changed, 73 insertions(+), 49 deletions(-)

diff --git a/tools/testing/selftests/futex/functional/futex_wait.c b/tools/testing/selftests/futex/functional/futex_wait.c index 685140d9b93d..17a465313a59 100644 --- a/tools/testing/selftests/futex/functional/futex_wait.c +++ b/tools/testing/selftests/futex/functional/futex_wait.c @@ -48,7 +48,7 @@ static void *waiterfn(void *arg) int main(int argc, char *argv[]) { int res, ret = RET_PASS, fd, c, shm_id;

• u_int32_t f_private = 0, *shared_data;

• u_int32_t f_private = 0, *shared_data = NULL; unsigned int flags = FUTEX_PRIVATE_FLAG; pthread_t waiter; void *shm;

@@ -96,32 +96,35 @@ int main(int argc, char *argv[]) /* Testing an anon page shared memory */ shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666); if (shm_id < 0) {

• perror("shmget");
  

• exit(1);
  

• }
• shared_data = shmat(shm_id, NULL, 0);

• if (errno == ENOSYS) {
  

• 	ksft_test_result_skip("Kernel does not support System V shared memory\n");
  

• } else {
  

• 	ksft_test_result_fail("shmget() failed with error: %s\n", strerror(errno));
  

• 	ret = RET_FAIL;
  

kselftest.h is already keeping track of the failure status. Just call ksft_finished() at the end. Also the whole perror()/exit(1) pattern doesn't really make sense in a kselftest.

• }
  

• } else {

• shared_data = shmat(shm_id, NULL, 0);
  

(...)