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 <[email protected]>
Signed-off-by: Justin Stitt <[email protected]>
---
Note: Previous RFC
https://lore.kernel.org/r/[email protected]
---
tools/testing/selftests/rseq/param_test.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/tools/testing/selftests/rseq/param_test.c
b/tools/testing/selftests/rseq/param_test.c
index bf951a490bb4..20403d58345c 100644
--- 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;
---
base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c
change-id: 20230908-kselftest-param_test-c-1763b62e762f
Best regards,
--
Justin Stitt <[email protected]>
