linux-kernel - Re: [PATCH v5 0/8] Faultable Tracepoints

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Message-ID: <16d0d924-f39b-4e0a-a488-74513f1214a6@efficios.com>
Date: Wed, 28 Aug 2024 09:52:49 -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>,
 Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>,
 bpf@...r.kernel.org, Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH v5 0/8] Faultable Tracepoints

On 2024-06-27 03:25, Steven Rostedt wrote:
> On Wed, 26 Jun 2024 14:59:33 -0400
> Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:
> 
>> Wire up the system call tracepoints with Tasks Trace RCU to allow
>> the ftrace, perf, and eBPF tracers to handle page faults.
>>
>> This series does the initial wire-up allowing tracers to handle page
>> faults, but leaves out the actual handling of said page faults as future
>> work.
>>
>> I have tested this against a feature branch of lttng-modules which
>> implements handling of page faults for the filename argument of the
>> openat(2) system call.
>>
>> This v5 addresses comments from the previous round of review [1].
> 
> Hi Mathieu,
> 
> Can you resend this and Cc linux-trace-kernel@...r.kernel.org?

Sure, will do for v6. Thanks!

Mathieu

> 
> That would put it into our patchwork and makes it work with our workflow.
> 
>   https://patchwork.kernel.org/project/linux-trace-kernel/list/
> 
> Thanks,
> 
> -- Steve
> 
> 
>>
>> Steven Rostedt suggested separating tracepoints into two separate
>> sections. It is unclear how that approach would prove to be an
>> improvement over the currently proposed approach, so those changes were
>> not incorporated. See [2] for my detailed reply.
>>
>> In the previous round, Peter Zijlstra suggested use of SRCU rather than
>> Tasks Trace RCU. See my reply about the distinction between SRCU and
>> Tasks Trace RCU [3] and this explanation from Paul E. McKenney about the
>> purpose of Tasks Trace RCU [4].
>>
>> The macros DEFINE_INACTIVE_GUARD and activate_guard are added to
>> cleanup.h for use in the __DO_TRACE() macro. Those appear to be more
>> flexible than the guard_if() proposed by Peter Zijlstra in the previous
>> round of review [5].
>>
>> This series is based on kernel v6.9.6.

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