selftests/rseq: fix kselftest Clang build warnings

When building with Clang, I am getting many warnings from the selftests/rseq tree.

Here's one such example from rseq tree:
|  param_test.c:1234:10: error: address argument to atomic operation must be a pointer to _Atomic type ('intptr_t *' (aka 'long *') invalid)
|   1234 |         while (!atomic_load(&args->percpu_list_ptr)) {}
|        |                 ^           ~~~~~~~~~~~~~~~~~~~~~~
|  /usr/local/google/home/justinstitt/repos/tc-build/build/llvm/final/lib/clang/18/include/stdatomic.h:140:29: note: expanded from macro 'atomic_load'
|    140 | #define atomic_load(object) __c11_atomic_load(object, __ATOMIC_SEQ_CST)
|        |                             ^                 ~~~~~~

Use compiler builtins `__atomic_load_n()` and `__atomic_store_n()` with
accompanying __ATOMIC_ACQUIRE and __ATOMIC_RELEASE, respectively. This
will fix the warnings because the compiler builtins do not expect their
arguments to have _Atomic type. This should also make TSAN happier.

Link: https://github.com/ClangBuiltLinux/linux/issues/1698
Link: https://github.com/ClangBuiltLinux/continuous-integration2/issues/61
Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

diff --git a/tools/testing/selftests/rseq/param_test.c b/tools/testing/selftests/rseq/param_test.c
index bf951a490bb4394d6ba8305429aa352d8e5f8be0..20403d58345cd523186b9423750ea7ad669cdd96 100644 (file)
--- a/tools/testing/selftests/rseq/param_test.c
+++ b/tools/testing/selftests/rseq/param_test.c
@@ -1231,7 +1231,7 @@ void *test_membarrier_worker_thread(void *arg)
        }
 
        /* Wait for initialization. */
-       while (!atomic_load(&args->percpu_list_ptr)) {}
+       while (!__atomic_load_n(&args->percpu_list_ptr, __ATOMIC_ACQUIRE)) {}
 
        for (i = 0; i < iters; ++i) {
                int ret;
@@ -1299,22 +1299,22 @@ void *test_membarrier_manager_thread(void *arg)
        test_membarrier_init_percpu_list(&list_a);
        test_membarrier_init_percpu_list(&list_b);
 
-       atomic_store(&args->percpu_list_ptr, (intptr_t)&list_a);
+       __atomic_store_n(&args->percpu_list_ptr, (intptr_t)&list_a, __ATOMIC_RELEASE);
 
-       while (!atomic_load(&args->stop)) {
+       while (!__atomic_load_n(&args->stop, __ATOMIC_ACQUIRE)) {
                /* list_a is "active". */
                cpu_a = rand() % CPU_SETSIZE;
                /*
                 * As list_b is "inactive", we should never see changes
                 * to list_b.
                 */
-               if (expect_b != atomic_load(&list_b.c[cpu_b].head->data)) {
+               if (expect_b != __atomic_load_n(&list_b.c[cpu_b].head->data, __ATOMIC_ACQUIRE)) {
                        fprintf(stderr, "Membarrier test failed\n");
                        abort();
                }
 
                /* Make list_b "active". */
-               atomic_store(&args->percpu_list_ptr, (intptr_t)&list_b);
+               __atomic_store_n(&args->percpu_list_ptr, (intptr_t)&list_b, __ATOMIC_RELEASE);
                if (rseq_membarrier_expedited(cpu_a) &&
                                errno != ENXIO /* missing CPU */) {
                        perror("sys_membarrier");
@@ -1324,27 +1324,27 @@ void *test_membarrier_manager_thread(void *arg)
                 * Cpu A should now only modify list_b, so the values
                 * in list_a should be stable.
                 */
-               expect_a = atomic_load(&list_a.c[cpu_a].head->data);
+               expect_a = __atomic_load_n(&list_a.c[cpu_a].head->data, __ATOMIC_ACQUIRE);
 
                cpu_b = rand() % CPU_SETSIZE;
                /*
                 * As list_a is "inactive", we should never see changes
                 * to list_a.
                 */
-               if (expect_a != atomic_load(&list_a.c[cpu_a].head->data)) {
+               if (expect_a != __atomic_load_n(&list_a.c[cpu_a].head->data, __ATOMIC_ACQUIRE)) {
                        fprintf(stderr, "Membarrier test failed\n");
                        abort();
                }
 
                /* Make list_a "active". */
-               atomic_store(&args->percpu_list_ptr, (intptr_t)&list_a);
+               __atomic_store_n(&args->percpu_list_ptr, (intptr_t)&list_a, __ATOMIC_RELEASE);
                if (rseq_membarrier_expedited(cpu_b) &&
                                errno != ENXIO /* missing CPU*/) {
                        perror("sys_membarrier");
                        abort();
                }
                /* Remember a value from list_b. */
-               expect_b = atomic_load(&list_b.c[cpu_b].head->data);
+               expect_b = __atomic_load_n(&list_b.c[cpu_b].head->data, __ATOMIC_ACQUIRE);
        }
 
        test_membarrier_free_percpu_list(&list_a);
@@ -1401,7 +1401,7 @@ void test_membarrier(void)
                }
        }
 
-       atomic_store(&thread_args.stop, 1);
+       __atomic_store_n(&thread_args.stop, 1, __ATOMIC_RELEASE);
        ret = pthread_join(manager_thread, NULL);
        if (ret) {
                errno = ret;