From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 58D464087F; Tue, 7 May 2024 04:04:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715054700; cv=none; b=awv+L29xA5iX5LWSDDrQQOz2Eu9L6+kd9wrQJjzgBbm0fZ0ugCaAR/uCnXhz8R/V/BbzjEnJSvc5g4uh0T8HMJUHg6LtJhaEH9SAOF8Gue11xHQL7WqJIMkU5CfGJn/v+0DG8TCcjrpBxX8hEnZi2SxoVF2hCk6H5GkKzdV1nNA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715054700; c=relaxed/simple; bh=RVnEF18pmo4hzHCpqUvXE5nta1BVMS7Kjs1hKQO8KSs=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=ZeVXUOMXn0n04nSH1jD1XVWr6moG/5j4a7q8O30K//rda31cfLBxXy/WrymQW4z4E1/LA44kLDUbIOwTU0aerGlyP1e2l2fVh5sLG7282JCu1+WOD+KRtWnVm0KfOlmBeIbOvLCb6goi9GD3ep7cFuVywc858deygNG1mPFjFl8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=U3RidpiQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="U3RidpiQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F5AFC2BBFC; Tue, 7 May 2024 04:04:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1715054699; bh=RVnEF18pmo4hzHCpqUvXE5nta1BVMS7Kjs1hKQO8KSs=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=U3RidpiQoAFe0PkC0w2ZDoeNacGei0vDvEgwD/KvUkQhdB8m1pnbQG1TWPxA8jz1n weACrG3kV9Cb7geopsoTeOxF4XlvDLShrf4S+bK1+wA/j+fOySHxZRCpa9GrFHiS63 4ZKCaUkA9h1H4U/+Wm+rsQmrYzN1AMzozd4H0G+DAucQAiZRacwOJJ4PCW6cTonuOr WlCEjB/zGkUzNGuwrLYwsSblHVNcyFUh6LyCzSx/8qIeel2kVtA6pfq+QSdFzCzjAU 69gZqSCdOaoMOEmCko8HIxww/2wsyv9kyBjjXilDqM6Rn2B21U6wQCKH4EPZECh0j6 5awf+eCDVoWrQ== Message-ID: <8201104dcc0b2b1e26a915315083e2098fb420b3.camel@kernel.org> Subject: Re: [PATCH bpf-next v4 3/3] selftests/bpf: Support nonblock for send_recv_data From: Geliang Tang To: Martin KaFai Lau Cc: Geliang Tang , Andrii Nakryiko , Eduard Zingerman , Mykola Lysenko , Alexei Starovoitov , Daniel Borkmann , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , bpf@vger.kernel.org, mptcp@lists.linux.dev, linux-kselftest@vger.kernel.org Date: Tue, 07 May 2024 12:04:48 +0800 In-Reply-To: <12aab271-da72-49b4-ac91-2091b6889856@linux.dev> References: <9cd358958245f8ec87c4f553779aa4243f967a2f.1712729342.git.tanggeliang@kylinos.cn> <12aab271-da72-49b4-ac91-2091b6889856@linux.dev> Autocrypt: addr=geliang@kernel.org; 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charset="UTF-8" User-Agent: Evolution 3.52.0-1build2 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 > > > > 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 > > --- > >   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; > >    } > >   > >