From: Peter Zijlstra <peterz@infradead.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Jiri Olsa <olsajiri@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Ingo Molnar <mingo@redhat.com>, bpf <bpf@vger.kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [RFC] ftrace: Add support to keep some functions out of ftrace
Date: Mon, 15 Aug 2022 16:33:09 +0200 [thread overview]
Message-ID: <YvpZJQGQdVaa2Oh4@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <CAADnVQJfvn2RYydqgO-nS_K+C8WJL7BdCnR44MiMF4rnAwWM5A@mail.gmail.com>
On Mon, Aug 15, 2022 at 07:25:24AM -0700, Alexei Starovoitov wrote:
> On Mon, Aug 15, 2022 at 5:37 AM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Mon, Aug 15, 2022 at 11:44:32AM +0200, Jiri Olsa wrote:
> > > On Mon, Aug 15, 2022 at 10:03:17AM +0200, Peter Zijlstra wrote:
> > > > On Sat, Aug 13, 2022 at 03:02:52PM -0400, Steven Rostedt wrote:
> > > > > On Fri, 12 Aug 2022 23:18:15 +0200
> > > > > Jiri Olsa <olsajiri@gmail.com> wrote:
> > > > >
> > > > > > the patch below moves the bpf function into sepatate object and switches
> > > > > > off the -mrecord-mcount for it.. so the function gets profile call
> > > > > > generated but it's not visible to ftrace
> > > >
> > > > Why ?!?
> > >
> > > there's bpf dispatcher code that updates bpf_dispatcher_xdp_func
> > > function with bpf_arch_text_poke and that can race with ftrace update
> > > if the function is traced
> >
> > I thought bpf_arch_text_poke() wasn't allowed to touch kernel code and
> > ftrace is in full control of it ?
>
> ftrace is not in "full control" of nop5 and must not be.
It is in full control of the 'call __fentry__'. Absolute full NAK on you
trying to make it otherwise.
> Soon we will have nop5 in the middle of the function.
> ftrace must not touch it.
How are you generating that NOP and what for?
next prev parent reply other threads:[~2022-08-15 14:33 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-22 11:08 [RFC] ftrace: Add support to keep some functions out of ftrace Jiri Olsa
2022-07-22 11:26 ` Steven Rostedt
2022-07-22 16:04 ` Alexei Starovoitov
2022-07-22 16:08 ` Steven Rostedt
2022-07-22 16:25 ` Steven Rostedt
2022-07-22 16:53 ` Alexei Starovoitov
2022-07-22 17:14 ` Steven Rostedt
2022-07-22 21:05 ` Jiri Olsa
2022-07-22 21:41 ` Steven Rostedt
2022-07-23 3:53 ` Steven Rostedt
2022-07-23 3:56 ` Steven Rostedt
2022-07-25 7:00 ` Jiri Olsa
2022-07-23 21:39 ` Jiri Olsa
2022-08-12 21:18 ` Jiri Olsa
2022-08-12 21:50 ` Steven Rostedt
2022-08-13 19:02 ` Steven Rostedt
2022-08-14 11:32 ` Steven Rostedt
2022-08-14 15:22 ` Jiri Olsa
2022-08-15 2:07 ` Chen Zhongjin
2022-08-15 8:04 ` Jiri Olsa
2022-08-15 11:01 ` Björn Töpel
2022-08-15 11:29 ` Jiri Olsa
2022-08-15 12:19 ` Björn Töpel
2022-08-15 12:30 ` Björn Töpel
2022-08-15 8:03 ` Peter Zijlstra
2022-08-15 9:44 ` Jiri Olsa
2022-08-15 12:37 ` Peter Zijlstra
2022-08-15 14:25 ` Alexei Starovoitov
2022-08-15 14:33 ` Peter Zijlstra [this message]
2022-08-15 14:45 ` Alexei Starovoitov
2022-08-15 15:02 ` Peter Zijlstra
2022-08-15 15:17 ` Alexei Starovoitov
2022-08-15 15:28 ` Peter Zijlstra
2022-08-15 15:35 ` Alexei Starovoitov
2022-08-15 15:44 ` Steven Rostedt
2022-08-15 15:53 ` Alexei Starovoitov
2022-08-15 16:13 ` Steven Rostedt
2022-08-15 15:48 ` Peter Zijlstra
2022-08-16 6:56 ` Jiri Olsa
2022-08-17 9:29 ` Jiri Olsa
2022-08-17 16:57 ` Alexei Starovoitov
2022-08-17 19:39 ` Jiri Olsa
2022-08-15 15:41 ` Peter Zijlstra
2022-08-15 15:49 ` Alexei Starovoitov
2022-08-15 16:08 ` Steven Rostedt
2022-08-18 20:27 ` Jiri Olsa
2022-08-18 20:50 ` Steven Rostedt
2022-08-18 21:00 ` Alexei Starovoitov
2022-08-18 21:05 ` Steven Rostedt
2022-08-18 21:32 ` Jiri Olsa
2022-08-19 11:45 ` Jiri Olsa
2022-08-23 17:23 ` Alexei Starovoitov
2022-08-26 8:00 ` Jiri Olsa
2022-08-18 21:14 ` Jiri Olsa
2022-08-15 15:32 ` Steven Rostedt
2022-07-22 16:26 ` Jiri Olsa
2022-07-22 16:37 ` Steven Rostedt
2022-07-22 16:54 ` Alexei Starovoitov
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