From: Geliang Tang <geliang@kernel.org>
To: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Geliang Tang <tanggeliang@kylinos.cn>,
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>,
bpf@vger.kernel.org, mptcp@lists.linux.dev,
linux-kselftest@vger.kernel.org
Subject: Re: [PATCH bpf-next v4 3/3] selftests/bpf: Support nonblock for send_recv_data
Date: Tue, 07 May 2024 12:04:48 +0800 [thread overview]
Message-ID: <8201104dcc0b2b1e26a915315083e2098fb420b3.camel@kernel.org> (raw)
In-Reply-To: <12aab271-da72-49b4-ac91-2091b6889856@linux.dev>
On Wed, 2024-04-10 at 14:34 -0700, Martin KaFai Lau wrote:
> On 4/9/24 11:13 PM, Geliang Tang wrote:
> > From: Geliang Tang <tanggeliang@kylinos.cn>
> >
> > Some tests, such as the MPTCP bpf tests, require send_recv_data
> > helper
> > to run in nonblock mode.
> >
> > This patch adds nonblock support for send_recv_data(). Check if it
> > is
> > currently in nonblock mode, and if so, ignore EWOULDBLOCK to
> > continue
> > sending and receiving.
> >
> > Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
> > ---
> > tools/testing/selftests/bpf/network_helpers.c | 9 ++++++++-
> > 1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/bpf/network_helpers.c
> > b/tools/testing/selftests/bpf/network_helpers.c
> > index 137cd18ef3f2..ca16ef2b648e 100644
> > --- a/tools/testing/selftests/bpf/network_helpers.c
> > +++ b/tools/testing/selftests/bpf/network_helpers.c
> > @@ -555,6 +555,7 @@ struct send_recv_arg {
> > static void *send_recv_server(void *arg)
> > {
> > struct send_recv_arg *a = (struct send_recv_arg *)arg;
> > + int flags = fcntl(a->fd, F_GETFL);
> > ssize_t nr_sent = 0, bytes = 0;
> > char batch[1500];
> > int err = 0, fd;
> > @@ -578,6 +579,8 @@ static void *send_recv_server(void *arg)
> > if (nr_sent == -1 && errno == EINTR)
> > continue;
> > if (nr_sent == -1) {
> > + if (flags & O_NONBLOCK && errno ==
> > EWOULDBLOCK)
>
> I still don't see why it needs to be a non blocking IO. mptcp should
> work
> with blocking IO also, no? Does it really need non blocking IO to
> make
> mptcp test work? I would rather stay with blocking IO in selftest as
> much as
> possible for simplicity reason.
>
> I am afraid the root cause of the EAGAIN thread has not been figured
> out yet:
> https://lore.kernel.org/all/b3943f9a8bf595212b00e96ba850bf32893312cc.camel@kernel.org/
>
> Lets drop patch 3 until it is understood why mptcp needs EAGAIN or
> non-blocking IO.
> It feels like there is some flakiness and it should be understood and
> avoided.
Hi Martin,
I finally found the root cause of this issue. It is indeed an MPTCP
bug. It took me a long time to debug, and the fix is here:
https://patchwork.kernel.org/project/mptcp/patch/0ccc1c26d27d6ee7be22806a97983d37c6ca548c.1715053270.git.tanggeliang@kylinos.cn/
Thank you for insisting on not accepting these work around patches from
me in the user space, almost hiding a kernel bug.
-Geliang
>
> Other than the comment in patch 2, the first two patches lgtm. Please
> respin with
> the first two patches.
>
> > + continue;
> > err = -errno;
> > break;
> > }
> > @@ -599,6 +602,7 @@ static void *send_recv_server(void *arg)
> >
> > int send_recv_data(int lfd, int fd, uint32_t total_bytes)
> > {
> > + int flags = fcntl(lfd, F_GETFL);
> > ssize_t nr_recv = 0, bytes = 0;
> > struct send_recv_arg arg = {
> > .fd = lfd,
> > @@ -622,8 +626,11 @@ int send_recv_data(int lfd, int fd, uint32_t
> > total_bytes)
> > MIN(total_bytes - bytes,
> > sizeof(batch)), 0);
> > if (nr_recv == -1 && errno == EINTR)
> > continue;
> > - if (nr_recv == -1)
> > + if (nr_recv == -1) {
> > + if (flags & O_NONBLOCK && errno ==
> > EWOULDBLOCK)
> > + continue;
> > break;
> > + }
> > bytes += nr_recv;
> > }
> >
>
>
next prev parent reply other threads:[~2024-05-07 4:04 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-10 6:13 [PATCH bpf-next v4 0/3] export send_recv_data Geliang Tang
2024-04-10 6:13 ` [PATCH bpf-next v4 1/3] selftests/bpf: Add struct send_recv_arg Geliang Tang
2024-04-10 6:13 ` [PATCH bpf-next v4 2/3] selftests/bpf: Export send_recv_data helper Geliang Tang
2024-04-10 21:20 ` Martin KaFai Lau
2024-04-10 6:13 ` [PATCH bpf-next v4 3/3] selftests/bpf: Support nonblock for send_recv_data Geliang Tang
2024-04-10 21:34 ` Martin KaFai Lau
2024-04-11 6:52 ` Geliang Tang
2024-04-22 6:50 ` Geliang Tang
2024-04-22 9:45 ` Matthieu Baerts
2024-04-22 10:04 ` Geliang Tang
2024-04-22 10:31 ` Matthieu Baerts
2024-04-22 10:34 ` Geliang Tang
2024-04-22 10:39 ` Matthieu Baerts
2024-04-23 2:58 ` Geliang Tang
2024-05-07 4:04 ` Geliang Tang [this message]
2024-04-10 17:53 ` [PATCH bpf-next v4 0/3] export send_recv_data MPTCP CI
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