linux-kernel - Re: [PATCH v1 2/8] tracing/ftrace: guard syscall probe with preempt

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Message-ID: <4f1046e7-7b62-4db3-93d4-815dc8c27185@efficios.com>
Date: Fri, 4 Oct 2024 10:51:09 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, linux-kernel@...r.kernel.org,
 Peter Zijlstra <peterz@...radead.org>, Alexei Starovoitov <ast@...nel.org>,
 Yonghong Song <yhs@...com>, "Paul E . McKenney" <paulmck@...nel.org>,
 Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Namhyung Kim <namhyung@...nel.org>,
 Andrii Nakryiko <andrii.nakryiko@...il.com>, bpf@...r.kernel.org,
 Joel Fernandes <joel@...lfernandes.org>, linux-trace-kernel@...r.kernel.org,
 Michael Jeanson <mjeanson@...icios.com>
Subject: Re: [PATCH v1 2/8] tracing/ftrace: guard syscall probe with
 preempt_notrace

On 2024-10-04 16:52, Steven Rostedt wrote:
> On Fri, 4 Oct 2024 10:19:36 -0400
> Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:
> 
>> The eBPF people want to leverage this. When I last discussed this with
>> eBPF maintainers, they were open to adapt eBPF after this infrastructure
>> series is merged. Based on this eBPF attempt from 2022:
>>
>> https://lore.kernel.org/lkml/c323bce9-a04e-b1c3-580a-783fde259d60@fb.com/
> 
> Sorry, I wasn't part of that discussion.
> 
>>
>> The sframe code is just getting in shape (2024), but is far from being ready.
>>
>> Everyone appears to be waiting for this infrastructure work to go in
>> before they can build on top. Once this infrastructure is available,
>> multiple groups can start working on introducing use of this into their
>> own code in parallel.
>>
>> Four years into this effort, and this is the first time we're told we need
>> to adapt in-tree tracers to handle the page faults before this can go in.
>>
>> Could you please stop moving the goal posts ?
> 
> I don't think I'm moving the goal posts. I was mentioning to show an
> in-tree user. If BPF wants this, I'm all for it. The only thing I saw was a
> generalization in the cover letter about perf, bpf and ftrace using
> faultible tracepoints. I just wanted to see a path for that happening.

AFAIU eBPF folks are very eager to start making use of this, so we won't
have to wait long.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com