Re: [PATCH] selftests:arm64: Test PR_SVE_VL_INHERIT after a double fork

Will Deacon
2024-04-30T12:20:45Z

On Mon, Apr 29, 2024 at 04:40:12AM +0000, Dorine Tipo wrote:
> Add a new test, double_fork_test() to check the inheritance of the SVE
> vector length after a double fork.
> The `EXPECTED_TESTS` macro has been updated to account for this additional
> test.
> This patch addresses task 7 on the TODO list.
>
> Signed-off-by: Dorine Tipo <dorine.a.tipo@gmail.com>
> ---
> tools/testing/selftests/arm64/fp/za-fork.c | 95 +++++++++++++++++++++-
> 1 file changed, 94 insertions(+), 1 deletion(-)

I haven't tried compiling this, but some of the code looks a little off:

> diff --git a/tools/testing/selftests/arm64/fp/za-fork.c b/tools/testing/selftests/arm64/fp/za-fork.c
> index 587b94648222..35229e570dcf 100644
> --- a/tools/testing/selftests/arm64/fp/za-fork.c
> +++ b/tools/testing/selftests/arm64/fp/za-fork.c
> @@ -11,7 +11,7 @@
>
> #include "kselftest.h"
>
> -#define EXPECTED_TESTS 1
> +#define EXPECTED_TESTS 2
>
> int fork_test(void);
> int verify_fork(void);
> @@ -69,6 +69,97 @@ int fork_test_c(void)
> }
> }
>
> +int double_fork_test(void)
> +{
> + pid_t newpid, grandchild_pid, waiting;
> + int ret, child_status, parent_result;
> +
> + ret = prctl(PR_SVE_SET_VL, vl | PR_SVE_VL_INHERIT);
> + if (ret < 0)
> + ksft_exit_fail_msg("Failed to set SVE VL %d\n", vl);
> +
> + newpid = fork();
> + if (newpid == 0) {
> + /* In child */
> + if (!verify_fork()) {
> + ksft_print_msg("ZA state invalid in child\n");
> + exit(0);
> + }
> +
> + grandchild_pid = fork();
> + if (grandchild_pid == 0) {
> + /* in grandchild */
> + if (!verfy_fork()) {
> + ksft_print_msg("ZA state invalid in grandchild\n");
> + exit(0);
> + }
> +
> + ret = prctl(PR_SVE_GET_VL);
> + if (ret & PR_SVE_VL_INHERIT) {
> + ksft_print_msg("prctl() reports _INHERIT\n");
> + return;

Missing return value?

> + }
> + ksft_print_msg("prctl() does not report _INHERIT\n");

Indentation.

> +
> + } else if (grandchild_pid < 0) {
> + ksft_print_msg("fork() failed in first child: %d\n", grandchild_pid);
> + return 0;
> + }
> +
> + /* Wait for the grandchild process to exit */
> + waiting = waitpid(grandchild_pid, &child_status, 0);
> + if (waiting < 0) {
> + if (errno == EINTR)
> + continue;

'continue' outside of a loop?

> + ksft_print_msg("waitpid() failed: %d\n", errno);
> + return 0;
> + }
> + if (waiting != grandchild_pid) {
> + ksft_print_msg("waitpid() returned wrong PID\n");
> + return 0;
> + }
> +
> + if (!WIFEXITED(child_status)) {
> + ksft_print_msg("grandchild did not exit\n");
> + return 0;
> + }
> +
> + exit(1);
> + }

Stray '}' ?

Will