Re: [PATCH bpf-next] selftests/bpf: Handle EAGAIN in bpf_tcp_ca

From: Martin KaFai Lau <martin.lau@linux.dev>
To: Geliang Tang <geliang@kernel.org>
Cc: Geliang Tang <tanggeliang@kylinos.cn>,
	bpf@vger.kernel.org, mptcp@lists.linux.dev,
	Andrii Nakryiko <andrii@kernel.org>,
	Eduard Zingerman <eddyz87@gmail.com>,
	Mykola Lysenko <mykolal@fb.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Song Liu <song@kernel.org>,
	Yonghong Song <yonghong.song@linux.dev>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>,
	Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
	Jiri Olsa <jolsa@kernel.org>, Shuah Khan <shuah@kernel.org>
Subject: Re: [PATCH bpf-next] selftests/bpf: Handle EAGAIN in bpf_tcp_ca
Date: Thu, 28 Mar 2024 09:55:32 -0700	[thread overview]
Message-ID: <e6074193-7530-4c85-9429-9393e24c172d@linux.dev> (raw)
In-Reply-To: <78a17486bd12d7afb4cce565d58dac3f15e55c49.1711620349.git.tanggeliang@kylinos.cn>

On 3/28/24 3:23 AM, Geliang Tang wrote:
> From: Geliang Tang <tanggeliang@kylinos.cn>
> 
> bpf_tcp_ca tests may emit EAGAIN sometimes. In that case, tests fail with
> "bytes != total_bytes" errors. Sending should continue, not break when
> errno is EAGAIN. This patch can make bpf_tcp_ca tests stable.
> 
> Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
> ---
>   tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
> index 077b107130f6..fbc219c2d53b 100644
> --- a/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_tcp_ca.c
> @@ -56,7 +56,7 @@ static void *server(void *arg)
>   	while (bytes < total_bytes && !READ_ONCE(stop)) {
>   		nr_sent = send(fd, &batch,
>   			       MIN(total_bytes - bytes, sizeof(batch)), 0);
> -		if (nr_sent == -1 && errno == EINTR)
> +		if (nr_sent == -1 && (errno == EINTR || errno == EAGAIN))

This is a non blocking socket. EAGAIN is hitting the timeout situation?

The default timeout is 3s and it has not been changed after the recent 
connect_fd_to_fd and start_server simplifications. I don't find bpf CI failing 
in this test in the last month also.

I would prefer to fail after timeout instead of keep retrying. Do you really hit 
that in your environment for this specific bpf_tcp_ca test? There are many tests 
using this timeout value also.