Re: [PATCH 1/2] selftest/futex: Make the error check more precise for futex_numa_mpol

[Waiman Long <llong@redhat.com>]

On 9/1/25 4:33 PM, André Almeida wrote:
> Instead of just checking if the syscall failed as expected, check as
> well what is the error code returned, to check if it's match the
> expectation and it's failing in the correct error path inside the
> kernel.
>
> Signed-off-by: André Almeida <andrealmeid@igalia.com>
> ---
> This patch is aimed for 6.18
> ---
>   .../futex/functional/futex_numa_mpol.c        | 36 +++++++++++--------
>   1 file changed, 21 insertions(+), 15 deletions(-)
>
> diff --git a/tools/testing/selftests/futex/functional/futex_numa_mpol.c b/tools/testing/selftests/futex/functional/futex_numa_mpol.c
> index 802c15c82190..c84441751235 100644
> --- a/tools/testing/selftests/futex/functional/futex_numa_mpol.c
> +++ b/tools/testing/selftests/futex/functional/futex_numa_mpol.c
> @@ -77,7 +77,7 @@ static void join_max_threads(void)
>   	}
>   }
>   
> -static void __test_futex(void *futex_ptr, int must_fail, unsigned int futex_flags)
> +static void __test_futex(void *futex_ptr, int err_value, unsigned int futex_flags)
>   {
>   	int to_wake, ret, i, need_exit = 0;
>   
> @@ -88,11 +88,17 @@ static void __test_futex(void *futex_ptr, int must_fail, unsigned int futex_flag
>   
>   	do {
>   		ret = futex2_wake(futex_ptr, to_wake, futex_flags);
> -		if (must_fail) {
> -			if (ret < 0)
> -				break;
> -			ksft_exit_fail_msg("futex2_wake(%d, 0x%x) should fail, but didn't\n",
> -					   to_wake, futex_flags);
> +
> +		if (err_value) {
> +			if (ret >= 0)
> +				ksft_exit_fail_msg("futex2_wake(%d, 0x%x) should fail, but didn't\n",
> +						   to_wake, futex_flags);
> +
> +			if (errno != err_value)
> +				ksft_exit_fail_msg("futex2_wake(%d, 0x%x) expected error was %d, but returned %d (%s)\n",
> +						   to_wake, futex_flags, err_value, errno, strerror(errno));
> +
> +			break;

If (ret >= 0), the 2nd (errno != err_value) failure message will likely 
be printed too. Should we use "else if" so that only one error message 
will be printed?


>   		}
>   		if (ret < 0) {
>   			ksft_exit_fail_msg("Failed futex2_wake(%d, 0x%x): %m\n",
> @@ -106,12 +112,12 @@ static void __test_futex(void *futex_ptr, int must_fail, unsigned int futex_flag
>   	join_max_threads();
>   
>   	for (i = 0; i < MAX_THREADS; i++) {
> -		if (must_fail && thread_args[i].result != -1) {
> +		if (err_value && thread_args[i].result != -1) {
>   			ksft_print_msg("Thread %d should fail but succeeded (%d)\n",
>   				       i, thread_args[i].result);
>   			need_exit = 1;
>   		}
> -		if (!must_fail && thread_args[i].result != 0) {
> +		if (!err_value && thread_args[i].result != 0) {
>   			ksft_print_msg("Thread %d failed (%d)\n", i, thread_args[i].result);
>   			need_exit = 1;
>   		}
> @@ -120,14 +126,14 @@ static void __test_futex(void *futex_ptr, int must_fail, unsigned int futex_flag
>   		ksft_exit_fail_msg("Aborting due to earlier errors.\n");
>   }
>   
> -static void test_futex(void *futex_ptr, int must_fail)
> +static void test_futex(void *futex_ptr, int err_value)
>   {
> -	__test_futex(futex_ptr, must_fail, FUTEX2_SIZE_U32 | FUTEX_PRIVATE_FLAG | FUTEX2_NUMA);
> +	__test_futex(futex_ptr, err_value, FUTEX2_SIZE_U32 | FUTEX_PRIVATE_FLAG | FUTEX2_NUMA);
>   }
>   
> -static void test_futex_mpol(void *futex_ptr, int must_fail)
> +static void test_futex_mpol(void *futex_ptr, int err_value)
>   {
> -	__test_futex(futex_ptr, must_fail, FUTEX2_SIZE_U32 | FUTEX_PRIVATE_FLAG | FUTEX2_NUMA | FUTEX2_MPOL);
> +	__test_futex(futex_ptr, err_value, FUTEX2_SIZE_U32 | FUTEX_PRIVATE_FLAG | FUTEX2_NUMA | FUTEX2_MPOL);
>   }
>   
>   static void usage(char *prog)
> @@ -184,16 +190,16 @@ int main(int argc, char *argv[])
>   
>   	/* FUTEX2_NUMA futex must be 8-byte aligned */
>   	ksft_print_msg("Mis-aligned futex\n");
> -	test_futex(futex_ptr + mem_size - 4, 1);
> +	test_futex(futex_ptr + mem_size - 4, 22);
>   
>   	futex_numa->numa = FUTEX_NO_NODE;
>   	mprotect(futex_ptr, mem_size, PROT_READ);
>   	ksft_print_msg("Memory, RO\n");
> -	test_futex(futex_ptr, 1);
> +	test_futex(futex_ptr, 14);
>   
>   	mprotect(futex_ptr, mem_size, PROT_NONE);
>   	ksft_print_msg("Memory, no access\n");
> -	test_futex(futex_ptr, 1);
> +	test_futex(futex_ptr, 14);
>   
>   	mprotect(futex_ptr, mem_size, PROT_READ | PROT_WRITE);
>   	ksft_print_msg("Memory back to RW\n");

I believe it is better to use the error number mnemonic (EINVAL & 
EFAULT) instead of 22 and 14 as argument to make the code easier to read.

Cheers,
Longman