Re: [PATCH v12 3/3] tracing: Centralize preemptirq tracepoints and unify their usage

From: Joel Fernandes <joelaf@google.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Joel Fernandes <joel@joelfernandes.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"Cc: Android Kernel" <kernel-team@android.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	Byungchul Park <byungchul.park@lge.com>,
	Ingo Molnar <mingo@redhat.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Paul McKenney <paulmck@linux.vnet.ibm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Glexiner <tglx@linutronix.de>,
	Tom Zanussi <tom.zanussi@linux.intel.com>
Subject: Re: [PATCH v12 3/3] tracing: Centralize preemptirq tracepoints and unify their usage
Date: Tue, 07 Aug 2018 10:10:59 -0400	[thread overview]
Message-ID: <446AE5F2-39E0-46B6-8E0B-207E003DBF20@google.com> (raw)
In-Reply-To: <20180807094954.5137972d@gandalf.local.home>

On August 7, 2018 9:49:54 AM EDT, Steven Rostedt <rostedt@goodmis.org> wrote:
>On Tue, 7 Aug 2018 06:33:35 -0700
>Joel Fernandes <joelaf@google.com> wrote:
>
>> Thanks, also one more thing I noticed in your patch,
>> lockdep_hardirqs_off needs to be called before all other probes but
>> you're calling it after. This is why I registered it with INT_MAX:
>> 
>> register_trace_prio_irq_disable(lockdep_hardirqs_off, NULL, INT_MAX);
>> 
>> Without it you may get annotation warnings. Thanks,
>
>Interesting. I was following the old way where we called the tracing
>code before calling the lockdep code (all hard coded and not from
>trace events). Is this have something to do with calling the code from
>a tracepoint?
>
>Do you have an example that could trigger the warning?
>

I remember the warnings but can't remember now how I triggered them. I think I saw them with the irqsoff tracer or irq trace events running, with lockdep turned on.

Also an irq disable probe that does a lockdep assert that irqs are disabled could trigger it?

thanks,

- Joel

>-- Steve

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