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Message-ID: <20250809071727.2422511-1-wakel@google.com>
Date: Sat, 9 Aug 2025 15:17:27 +0800
From: Wake Liu <wakel@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.org>, Shuah Khan <shuah@...nel.org>,
linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Cc: Peter Zijlstra <peterz@...radead.org>, Darren Hart <dvhart@...radead.org>,
Davidlohr Bueso <dave@...olabs.net>,
"André Almeida" <andrealmeid@...lia.com>, Wake Liu <wakel@...gle.com>
Subject: [PATCH v3] selftests/futex: Check for shmget support at runtime
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@...gle.com>
---
.../selftests/futex/functional/futex_wait.c | 57 ++++++++-------
.../selftests/futex/functional/futex_waitv.c | 73 ++++++++++++-------
2 files changed, 78 insertions(+), 52 deletions(-)
diff --git a/tools/testing/selftests/futex/functional/futex_wait.c b/tools/testing/selftests/futex/functional/futex_wait.c
index 685140d9b93d..2a834f074959 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 +96,37 @@ 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);
-
- *shared_data = 0;
- futex = shared_data;
-
- info("Calling shared (page anon) futex_wait on futex: %p\n", futex);
- if (pthread_create(&waiter, NULL, waiterfn, NULL))
- error("pthread_create failed\n", errno);
-
- usleep(WAKE_WAIT_US);
-
- info("Calling shared (page anon) futex_wake on futex: %p\n", futex);
- res = futex_wake(futex, 1, 0);
- if (res != 1) {
- ksft_test_result_fail("futex_wake shared (page anon) returned: %d %s\n",
- errno, strerror(errno));
- ret = RET_FAIL;
+ 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;
+ }
} else {
- ksft_test_result_pass("futex_wake shared (page anon) succeeds\n");
+ shared_data = shmat(shm_id, NULL, 0);
+
+ *shared_data = 0;
+ futex = shared_data;
+
+ info("Calling shared (page anon) futex_wait on futex: %p\n", futex);
+ if (pthread_create(&waiter, NULL, waiterfn, NULL))
+ error("pthread_create failed\n", errno);
+
+ usleep(WAKE_WAIT_US);
+
+ info("Calling shared (page anon) futex_wake on futex: %p\n", futex);
+ res = futex_wake(futex, 1, 0);
+ if (res != 1) {
+ if (res < 0)
+ ksft_test_result_fail("futex_wake shared (page anon) failed with res=%d: %m\n", res);
+ else
+ ksft_test_result_fail("futex_wake shared (page anon) returned %d, expected 1\n", res);
+ ret = RET_FAIL;
+ } else {
+ ksft_test_result_pass("futex_wake shared (page anon) succeeds\n");
+ }
}
-
/* Testing a file backed shared memory */
fd = open(SHM_PATH, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
if (fd < 0) {
@@ -161,7 +166,8 @@ int main(int argc, char *argv[])
}
/* Freeing resources */
- shmdt(shared_data);
+ if (shared_data)
+ shmdt(shared_data);
munmap(shm, sizeof(f_private));
remove(SHM_PATH);
close(fd);
@@ -169,3 +175,4 @@ int main(int argc, char *argv[])
ksft_print_cnts();
return ret;
}
+
diff --git a/tools/testing/selftests/futex/functional/futex_waitv.c b/tools/testing/selftests/futex/functional/futex_waitv.c
index a94337f677e1..034dbfef40cb 100644
--- a/tools/testing/selftests/futex/functional/futex_waitv.c
+++ b/tools/testing/selftests/futex/functional/futex_waitv.c
@@ -110,40 +110,58 @@ int main(int argc, char *argv[])
}
/* Shared waitv */
- for (i = 0; i < NR_FUTEXES; i++) {
- int shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666);
-
- if (shm_id < 0) {
- perror("shmget");
- exit(1);
+ bool shm_supported = true;
+ int shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666);
+
+ if (shm_id < 0) {
+ if (errno == ENOSYS) {
+ shm_supported = false;
+ 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;
+ shm_supported = false;
}
+ } else {
+ shmctl(shm_id, IPC_RMID, NULL);
+ }
- unsigned int *shared_data = shmat(shm_id, NULL, 0);
+ if (shm_supported) {
+ for (i = 0; i < NR_FUTEXES; i++) {
+ int shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666);
- *shared_data = 0;
- waitv[i].uaddr = (uintptr_t)shared_data;
- waitv[i].flags = FUTEX_32;
- waitv[i].val = 0;
- waitv[i].__reserved = 0;
- }
+ if (shm_id < 0) {
+ perror("shmget");
+ exit(1);
+ }
- if (pthread_create(&waiter, NULL, waiterfn, NULL))
- error("pthread_create failed\n", errno);
+ unsigned int *shared_data = shmat(shm_id, NULL, 0);
- usleep(WAKE_WAIT_US);
+ *shared_data = 0;
+ waitv[i].uaddr = (uintptr_t)shared_data;
+ waitv[i].flags = FUTEX_32;
+ waitv[i].val = 0;
+ waitv[i].__reserved = 0;
+ }
- res = futex_wake(u64_to_ptr(waitv[NR_FUTEXES - 1].uaddr), 1, 0);
- if (res != 1) {
- ksft_test_result_fail("futex_wake shared returned: %d %s\n",
- res ? errno : res,
- res ? strerror(errno) : "");
- ret = RET_FAIL;
- } else {
- ksft_test_result_pass("futex_waitv shared\n");
- }
+ if (pthread_create(&waiter, NULL, waiterfn, NULL))
+ error("pthread_create failed\n", errno);
- for (i = 0; i < NR_FUTEXES; i++)
- shmdt(u64_to_ptr(waitv[i].uaddr));
+ usleep(WAKE_WAIT_US);
+
+ res = futex_wake(u64_to_ptr(waitv[NR_FUTEXES - 1].uaddr), 1, 0);
+ if (res != 1) {
+ ksft_test_result_fail("futex_wake shared returned: %d %s\n",
+ res ? errno : res,
+ res ? strerror(errno) : "");
+ ret = RET_FAIL;
+ } else {
+ ksft_test_result_pass("futex_waitv shared\n");
+ }
+
+ for (i = 0; i < NR_FUTEXES; i++)
+ shmdt(u64_to_ptr(waitv[i].uaddr));
+ }
/* Testing a waiter without FUTEX_32 flag */
waitv[0].flags = FUTEX_PRIVATE_FLAG;
@@ -235,3 +253,4 @@ int main(int argc, char *argv[])
ksft_print_cnts();
return ret;
}
+
--
2.50.1.703.g449372360f-goog
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