Re: [PATCH net-next 2/4] selftests: drv-net: add a way to wait for a local process

Stanislav Fomichev
2025-02-18T21:10:16Z

On 02/18, Jakub Kicinski wrote:
> We use wait_port_listen() extensively to wait for a process
> we spawned to be ready. Not all processes will open listening
> sockets. Add a method of explicitly waiting for a child to
> be ready. Pass a FD to the spawned process and wait for it
> to write a message to us. FD number is passed via KSFT_READY_FD
> env variable.
>
> Make use of this method in the queues test to make it less flaky.
>
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> .../selftests/drivers/net/xdp_helper.c | 22 ++++++-
> tools/testing/selftests/drivers/net/queues.py | 46 ++++++---------
> tools/testing/selftests/net/lib/py/utils.py | 58 +++++++++++++++++--
> 3 files changed, 93 insertions(+), 33 deletions(-)
>
> diff --git a/tools/testing/selftests/drivers/net/xdp_helper.c b/tools/testing/selftests/drivers/net/xdp_helper.c
> index cf06a88b830b..8f77da4f798f 100644
> --- a/tools/testing/selftests/drivers/net/xdp_helper.c
> +++ b/tools/testing/selftests/drivers/net/xdp_helper.c
> @@ -14,6 +14,25 @@
> #define UMEM_SZ (1U << 16)
> #define NUM_DESC (UMEM_SZ / 2048)
>
> +/* Move this to a common header when reused! */
> +static void ksft_ready(void)
> +{
> + const char msg[7] = "ready\n";
> + char *env_str;
> + int fd;

[..]

> + env_str = getenv("KSFT_READY_FD");
> + if (!env_str)
> + return;
> +
> + fd = atoi(env_str);
> + if (!fd)
> + return;

optional nit: should these fail with error() instead of silent return?
Should guarantee that the caller is doing everything correctly.
(passing wait_init vs waiting for a port)