From: Alexei Starovoitov <ast@plumgrid.com>
To: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>,
Arnaldo Carvalho de Melo <acme@infradead.org>,
Jiri Olsa <jolsa@redhat.com>,
Linux API <linux-api@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 linux-trace 1/8] tracing: attach eBPF programs to tracepoints and syscalls
Date: Wed, 28 Jan 2015 22:39:34 -0800 [thread overview]
Message-ID: <CAMEtUuywGh9p9yQdeJJiKRdpZhmgJdQYWgf3W3U0uSTXkjF_uA@mail.gmail.com> (raw)
On Wed, Jan 28, 2015 at 9:39 PM, Masami Hiramatsu
<masami.hiramatsu.pt@hitachi.com> wrote:
>
> Maybe, would we need a reference counter for each event? :)
when we would want multiple users to attach different programs
to the same event, then yes.
Right now I'd rather have things simple.
> Actually, ftrace event is not similar to perf-event which ktap
> is based on, ftrace event interface is always exported via
> debugfs, this means users can share the event for different
> usage.
yes.I've been thinking to extend perf_event ioctl to attach programs,
but right now it's only supporting tracepoints and kprobe
seems not trivial to add.
So I went for tracefs style of attaching for now.
> One possible other solution is to add a instance-lock interface
> for each ftrace instance and lock it by bpf. Then, other users
> can not enable/disable the events in the instance.
the user space can synchronize itself via flock. kernel doesn't
need to arbitrate. If one user process attached a program
that auto-enabled an event and another process did
'echo 0 > enable', it's fine. I think it's a feature instead of a bug.
Both users are root anyway.
The more we talk about it, the more I like a new 'bpf' file
approach within tracefs (that I've mentioned in cover letter)
with auto-enable/disable logic to make it clear that
it's different from traditional global 'filter' file.
next reply other threads:[~2015-01-29 6:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-29 6:39 Alexei Starovoitov [this message]
-- strict thread matches above, loose matches on Subject: below --
2015-01-29 18:55 [PATCH v2 linux-trace 1/8] tracing: attach eBPF programs to tracepoints and syscalls Alexei Starovoitov
2015-01-29 7:04 Alexei Starovoitov
2015-01-29 12:35 ` Namhyung Kim
2015-01-29 4:40 Alexei Starovoitov
2015-01-29 5:39 ` Masami Hiramatsu
2015-01-29 6:41 ` Namhyung Kim
2015-01-28 4:06 [PATCH v2 linux-trace 0/8] tracing: attach eBPF programs to tracepoints/syscalls/kprobe Alexei Starovoitov
2015-01-28 4:06 ` [PATCH v2 linux-trace 1/8] tracing: attach eBPF programs to tracepoints and syscalls Alexei Starovoitov
2015-01-29 0:46 ` Namhyung Kim
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