From: Steven Rostedt <rostedt@goodmis.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Joel Fernandes, Google" <joel@joelfernandes.org>,
Michael Jeanson <mjeanson@efficios.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Alexei Starovoitov <ast@kernel.org>, Yonghong Song <yhs@fb.com>,
paulmck <paulmck@kernel.org>, Ingo Molnar <mingo@redhat.com>,
acme <acme@kernel.org>, Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
bpf <bpf@vger.kernel.org>
Subject: Re: [RFC PATCH 6/6] tracing: use sched-RCU instead of SRCU for rcuidle tracepoints
Date: Mon, 26 Oct 2020 16:44:59 -0400 [thread overview]
Message-ID: <20201026164459.1d514d0a@gandalf.local.home> (raw)
In-Reply-To: <73192641.37901.1603722487627.JavaMail.zimbra@efficios.com>
On Mon, 26 Oct 2020 10:28:07 -0400 (EDT)
Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
> I agree with Peter. Removing the trace_.*_rcuidle weirdness from the tracepoint
> API and fixing all callers to ensure they trace from a context where RCU is
> watching would simplify instrumentation of the Linux kernel, thus making it harder
> for subtle bugs to hide and be unearthed only when tracing is enabled. This is
Note, the lockdep RCU checking of a tracepoint is outside of it being
enabled or disable. So if a non rcuidle() tracepoint is in a location that
RCU is not watching, it will complain loudly, even if you don't enable that
tracepoint.
> AFAIU the general approach Thomas Gleixner has been aiming for recently, and I
> think it is a good thing.
>
> So if we consider this our target, and that the current state of things is that
> we need to have RCU watching around callback invocation, then removing the
> dependency on SRCU seems like an overall simplification which does not regress
> feature-wise nor speed-wise compared with what we have upstream today. The next
> steps would then be to audit all rcuidle tracepoints and make sure the context
> where they are placed has RCU watching already, so we can remove the tracepoint
Just remove the _rcuidle() from them, and lockdep will complain if they are
being called without RCU watching.
-- Steve
> rcuidle API. That would effectively remove the calls to rcu_irq_{enter,exit}_irqson
> from the tracepoint code.
>
> This is however beyond the scope of the proposed patch set.
>
> Thanks,
>
> Mathieu
>
next prev parent reply other threads:[~2020-10-26 20:45 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-23 19:53 [RFC PATCH 0/6] Sleepable tracepoints Michael Jeanson
2020-10-23 19:53 ` [RFC PATCH 1/6] tracing: introduce sleepable tracepoints Michael Jeanson
2020-10-26 22:43 ` Alexei Starovoitov
2020-10-27 13:37 ` Mathieu Desnoyers
2020-10-28 21:23 ` Alexei Starovoitov
2021-02-11 19:36 ` Mathieu Desnoyers
2020-11-02 18:51 ` Joel Fernandes
2020-10-23 19:53 ` [RFC PATCH 2/6] tracing: ftrace: add support for " Michael Jeanson
2020-10-23 19:53 ` [RFC PATCH 3/6] tracing: bpf-trace: " Michael Jeanson
2020-10-23 19:53 ` [RFC PATCH 4/6] tracing: perf: " Michael Jeanson
2020-10-23 19:53 ` [RFC PATCH 5/6] tracing: convert sys_enter/exit to " Michael Jeanson
2020-10-23 19:53 ` [RFC PATCH 6/6] tracing: use sched-RCU instead of SRCU for rcuidle tracepoints Michael Jeanson
2020-10-23 21:13 ` Joel Fernandes
2020-10-26 8:20 ` Peter Zijlstra
2020-10-26 14:28 ` Mathieu Desnoyers
2020-10-26 20:44 ` Steven Rostedt [this message]
2020-10-27 13:57 ` Mathieu Desnoyers
2020-11-02 18:43 ` Joel Fernandes
2020-10-26 12:05 ` [RFC PATCH 0/6] Sleepable tracepoints peter enderborg
2020-10-26 14:59 ` Mathieu Desnoyers
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