Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 11 Jul 2018 09:22:34 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Joel Fernandes <joel@joelfernandes.org>,
        linux-kernel@vger.kernel.org, Boqun Feng <boqun.feng@gmail.com>,
        Byungchul Park <byungchul.park@lge.com>,
        Ingo Molnar <mingo@redhat.com>,
        Julia Cartwright <julia@ni.com>,
        linux-kselftest@vger.kernel.org,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Thomas Glexiner <tglx@linutronix.de>,
        Tom Zanussi <tom.zanussi@linux.intel.com>
Subject: Re: [PATCH v9 5/7] tracing: Centralize preemptirq tracepoints and
 unify their usage
Message-ID: <20180711092234.11d4e34f@gandalf.local.home>
In-Reply-To: <20180711091944.4d8e78ef@gandalf.local.home>
References: <20180628182149.226164-1-joel@joelfernandes.org>
        <20180628182149.226164-6-joel@joelfernandes.org>
        <20180711131256.GH2476@hirez.programming.kicks-ass.net>
        <20180711091944.4d8e78ef@gandalf.local.home>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, 11 Jul 2018 09:19:44 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Wed, 11 Jul 2018 15:12:56 +0200
> Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Thu, Jun 28, 2018 at 11:21:47AM -0700, Joel Fernandes wrote:  
> > > One note, I have to check for lockdep recursion in the code that calls
> > > the trace events API and bail out if we're in lockdep recursion    
> > 
> > I'm not seeing any new lockdep_recursion checks...  
> 
> I believe he's talking about this part:
> 
> +void trace_hardirqs_on(void)
> +{
> +	if (lockdep_recursing(current) || !this_cpu_read(tracing_irq_cpu))
> +		return;
> +

And the reason he said this is new, IIUC, is because the old way we
could still do irqsoff tracing even if lockdep_recursion is set. Now,
irqsoff tracing is disable within lockdep_recursion.

-- Steve