From: Hao Luo <haoluo@google.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, KP Singh <kpsingh@kernel.org>,
Shakeel Butt <shakeelb@google.com>,
Joe Burton <jevburton.kernel@gmail.com>,
Stanislav Fomichev <sdf@google.com>, bpf <bpf@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC bpf-next v2 5/5] selftests/bpf: test for pinning for cgroup_view link
Date: Mon, 14 Feb 2022 12:23:29 -0800 [thread overview]
Message-ID: <CA+khW7jeptVgZziTqexXp2dNC0Kk+di8f8xkd2dTzXb8YR0Mjw@mail.gmail.com> (raw)
In-Reply-To: <CAADnVQK+Eh9qCuoBWZ1cRQ4h+fS5J+zy+GePEGXijZ_BD_5Q3w@mail.gmail.com>
On Mon, Feb 14, 2022 at 11:25 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Mon, Feb 14, 2022 at 10:29 AM Hao Luo <haoluo@google.com> wrote:
> > Hi Alexei,
> >
> > Actually, I found this almost worked, except that the tracepoints
> > cgroup_mkdir and cgroup_rmdir are not sleepable. They are inside a
> > spinlock's critical section with irq off. I guess one solution is to
> > offload the sleepable part of the bpf prog into a thread context. We
> > may create a dedicated kernel thread or use workqueue for this. Do you
> > have any advice?
>
> Are you referring to spin_lock in TRACE_CGROUP_PATH
> that protects global trace_cgroup_path[] buffer?
Yes, that's the spin_lock I am talking about.
> That is fixable.
> Do you actually need the string path returned by cgroup_path() in bpf prog?
> Maybe prog can call cgroup_path() by itself when necessary.
> Parsing strings isn't great anyway. The bpf prog probably needs the last
> part of the dir only. So cgrp->kn->name would do it?
> The TRACE_CGROUP_PATH wasn't designed to be turned on 24/7.
> That global spin_lock is not great for production use.
> No need to delegate sleepable bpf to thread context.
> Let's refactor that tracepoint a bit.
No, we don't need cgroup_path(). We are going to name the directories
by cgrp->kn->id. I can add a fast version for cgroup_xxx tracepoints,
which don't require the full path and can be turned on 24/7.
next prev parent reply other threads:[~2022-02-14 20:57 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-01 20:55 [PATCH RFC bpf-next v2 0/5] Extend cgroup interface with bpf Hao Luo
2022-02-01 20:55 ` [PATCH RFC bpf-next v2 1/5] bpf: Bpffs directory tag Hao Luo
2022-02-01 20:55 ` [PATCH RFC bpf-next v2 2/5] bpf: Introduce inherit list for dir tag Hao Luo
2022-02-01 20:55 ` [PATCH RFC bpf-next v2 3/5] bpf: cgroup_view iter Hao Luo
2022-02-01 20:55 ` [PATCH RFC bpf-next v2 4/5] bpf: Pin cgroup_view Hao Luo
2022-02-01 20:55 ` [PATCH RFC bpf-next v2 5/5] selftests/bpf: test for pinning for cgroup_view link Hao Luo
2022-02-03 18:04 ` Alexei Starovoitov
2022-02-03 22:46 ` Hao Luo
2022-02-04 3:33 ` Alexei Starovoitov
2022-02-04 18:26 ` Hao Luo
2022-02-06 4:29 ` Alexei Starovoitov
2022-02-08 20:07 ` Hao Luo
2022-02-08 21:20 ` Alexei Starovoitov
2022-02-08 21:34 ` Hao Luo
2022-02-14 18:29 ` Hao Luo
2022-02-14 19:24 ` Alexei Starovoitov
2022-02-14 20:23 ` Hao Luo [this message]
2022-02-14 20:27 ` Alexei Starovoitov
2022-02-14 20:39 ` Hao Luo
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CA+khW7jeptVgZziTqexXp2dNC0Kk+di8f8xkd2dTzXb8YR0Mjw@mail.gmail.com \
--to=haoluo@google.com \
--cc=alexei.starovoitov@gmail.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=jevburton.kernel@gmail.com \
--cc=kafai@fb.com \
--cc=kpsingh@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=sdf@google.com \
--cc=shakeelb@google.com \
--cc=songliubraving@fb.com \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).