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Message-ID: <20180525232036.GA252027@joelaf.mtv.corp.google.com>
Date: Fri, 25 May 2018 16:20:36 -0700
From: Joel Fernandes <joel@...lfernandes.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Joel Fernandes <joelaf@...gle.com>, linux-kernel@...r.kernel.org,
kernel-team@...roid.com, Boqun Feng <boqun.feng@...il.com>,
Byungchul Park <byungchul.park@....com>,
Erick Reyes <erickreyes@...gle.com>,
Ingo Molnar <mingo@...hat.com>,
Julia Cartwright <julia@...com>,
linux-kselftest@...r.kernel.org,
Masami Hiramatsu <mhiramat@...nel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Paul McKenney <paulmck@...ux.vnet.ibm.com>,
Peter Zijlstra <peterz@...radead.org>,
Shuah Khan <shuah@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Glexiner <tglx@...utronix.de>,
Todd Kjos <tkjos@...gle.com>,
Tom Zanussi <tom.zanussi@...ux.intel.com>, kernel-team@....com
Subject: Re: [PATCH v7 6/8] tracing: Centralize preemptirq tracepoints and
unify their usage
On Fri, May 25, 2018 at 08:43:39PM +0900, Namhyung Kim wrote:
> Hi Joel,
>
> On Wed, May 23, 2018 at 06:21:55PM -0700, Joel Fernandes wrote:
> > From: "Joel Fernandes (Google)" <joel@...lfernandes.org>
> >
> > This patch detaches the preemptirq tracepoints from the tracers and
> > keeps it separate.
> >
> > Advantages:
> > * Lockdep and irqsoff event can now run in parallel since they no longer
> > have their own calls.
> >
> > * This unifies the usecase of adding hooks to an irqsoff and irqson
> > event, and a preemptoff and preempton event.
> > 3 users of the events exist:
> > - Lockdep
> > - irqsoff and preemptoff tracers
> > - irqs and preempt trace events
> >
> > The unification cleans up several ifdefs and makes the code in preempt
> > tracer and irqsoff tracers simpler. It gets rid of all the horrific
> > ifdeferry around PROVE_LOCKING and makes configuration of the different
> > users of the tracepoints more easy and understandable. It also gets rid
> > of the time_* function calls from the lockdep hooks used to call into
> > the preemptirq tracer which is not needed anymore. The negative delta in
> > lines of code in this patch is quite large too.
> >
> [SNIP]
> >
> > #ifdef CONFIG_IRQSOFF_TRACER
> > +/*
> > + * We are only interested in hardirq on/off events:
> > + */
> > +static void tracer_hardirqs_on(void *none, unsigned long a0, unsigned long a1)
> > +{
> > + if (!preempt_trace() && irq_trace())
> > + stop_critical_timing(a0, a1);
> > +}
> > +
> > +static void tracer_hardirqs_off(void *none, unsigned long a0, unsigned long a1)
> > +{
> > + if (!preempt_trace() && irq_trace())
> > + start_critical_timing(a0, a1);
> > +}
> > +
> > static int irqsoff_tracer_init(struct trace_array *tr)
> > {
> > trace_type = TRACER_IRQS_OFF;
> >
> > + register_trace_irq_disable(tracer_hardirqs_off, NULL);
> > + register_trace_irq_enable(tracer_hardirqs_on, NULL);
> > return __irqsoff_tracer_init(tr);
> > }
> >
> > static void irqsoff_tracer_reset(struct trace_array *tr)
> > {
> > + unregister_trace_irq_disable(tracer_hardirqs_off, NULL);
> > + unregister_trace_irq_enable(tracer_hardirqs_on, NULL);
> > __irqsoff_tracer_reset(tr);
> > }
> >
> > @@ -692,19 +650,37 @@ static struct tracer irqsoff_tracer __read_mostly =
> > };
> > # define register_irqsoff(trace) register_tracer(&trace)
> > #else
> > +static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
> > +static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }
>
> Just a nitpick. These lines seem unnecessary since they're used
> only when CONFIG_IRQSOFF_TRACER is enabled AFAICS.
>
>
> > # define register_irqsoff(trace) do { } while (0)
> > -#endif
> > +#endif /* CONFIG_IRQSOFF_TRACER */
> >
> > #ifdef CONFIG_PREEMPT_TRACER
> > +static void tracer_preempt_on(void *none, unsigned long a0, unsigned long a1)
> > +{
> > + if (preempt_trace() && !irq_trace())
> > + stop_critical_timing(a0, a1);
> > +}
> > +
> > +static void tracer_preempt_off(void *none, unsigned long a0, unsigned long a1)
> > +{
> > + if (preempt_trace() && !irq_trace())
> > + start_critical_timing(a0, a1);
> > +}
> > +
> > static int preemptoff_tracer_init(struct trace_array *tr)
> > {
> > trace_type = TRACER_PREEMPT_OFF;
> >
> > + register_trace_preempt_disable(tracer_preempt_off, NULL);
> > + register_trace_preempt_enable(tracer_preempt_on, NULL);
> > return __irqsoff_tracer_init(tr);
> > }
> >
> > static void preemptoff_tracer_reset(struct trace_array *tr)
> > {
> > + unregister_trace_preempt_disable(tracer_preempt_off, NULL);
> > + unregister_trace_preempt_enable(tracer_preempt_on, NULL);
> > __irqsoff_tracer_reset(tr);
> > }
> >
> > @@ -729,21 +705,32 @@ static struct tracer preemptoff_tracer __read_mostly =
> > };
> > # define register_preemptoff(trace) register_tracer(&trace)
> > #else
> > +static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
> > +static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
>
> Ditto (for CONFIG_PREEMPT_TRACER).
>
> Thanks,
> Namhyung
Yes you're right, saves quite a few lines actually! I also inlined the
register_tracer macros, It seems much cleaner. I will fold the below diff but
let me know if there's anything else.
Thanks Namhyung!
- Joel
---8<-----------------------
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index d2d8284088f0..d0bcb51d1a2a 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -648,11 +648,6 @@ static struct tracer irqsoff_tracer __read_mostly =
.allow_instances = true,
.use_max_tr = true,
};
-# define register_irqsoff(trace) register_tracer(&trace)
-#else
-static inline void tracer_hardirqs_on(unsigned long a0, unsigned long a1) { }
-static inline void tracer_hardirqs_off(unsigned long a0, unsigned long a1) { }
-# define register_irqsoff(trace) do { } while (0)
#endif /* CONFIG_IRQSOFF_TRACER */
#ifdef CONFIG_PREEMPT_TRACER
@@ -703,11 +698,6 @@ static struct tracer preemptoff_tracer __read_mostly =
.allow_instances = true,
.use_max_tr = true,
};
-# define register_preemptoff(trace) register_tracer(&trace)
-#else
-static inline void tracer_preempt_on(unsigned long a0, unsigned long a1) { }
-static inline void tracer_preempt_off(unsigned long a0, unsigned long a1) { }
-# define register_preemptoff(trace) do { } while (0)
#endif /* CONFIG_PREEMPT_TRACER */
#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
@@ -753,18 +743,19 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
.allow_instances = true,
.use_max_tr = true,
};
-
-# define register_preemptirqsoff(trace) register_tracer(&trace)
-#else
-# define register_preemptirqsoff(trace) do { } while (0)
#endif
__init static int init_irqsoff_tracer(void)
{
- register_irqsoff(irqsoff_tracer);
- register_preemptoff(preemptoff_tracer);
- register_preemptirqsoff(preemptirqsoff_tracer);
-
+#ifdef CONFIG_IRQSOFF_TRACER
+ register_tracer(&irqsoff_tracer);
+#endif
+#ifdef CONFIG_PREEMPT_TRACER
+ register_tracer(&preemptoff_tracer);
+#endif
+#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
+ register_tracer(&preemptirqsoff_tracer);
+#endif
return 0;
}
core_initcall(init_irqsoff_tracer);
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