From: Steven Rostedt <rostedt@goodmis.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH 7/5] tracing: Make sure rcu_irq_enter() can work for trace_*_rcuidle() trace events
Date: Fri, 7 Apr 2017 13:26:13 -0400 [thread overview]
Message-ID: <20170407132613.4a9fa430@gandalf.local.home> (raw)
In-Reply-To: <1475342880.4473.1491585545139.JavaMail.zimbra@efficios.com>
On Fri, 7 Apr 2017 17:19:05 +0000 (UTC)
Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
> ----- On Apr 7, 2017, at 1:06 PM, rostedt rostedt@goodmis.org wrote:
>
> > From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
> >
> > Stack tracing discovered that there's a small location inside the RCU
> > infrastructure that calling rcu_irq_enter() does not work. As trace events
>
> that -> where
ok
>
> Do you have a link to the lkml thread where this stack tracing discovery
> happened ?
Actually it's this thread. But here:
Version 1 of the patch series:
http://lkml.kernel.org/r/20170406164237.874767449@goodmis.org
Version 2 of the patch series:
http://lkml.kernel.org/r/20170407140106.051135969@goodmis.org
>
> > use rcu_irq_enter() it must make sure that it is functionable. A check
>
> I don't think functionable is the word you are looking for here. Perhaps
> "must make sure that it can be invoked" ?
>
> > against rcu_irq_enter_disabled() is added with a WARN_ON_ONCE() as no trace
> > event should ever be used in that part of RCU. If the warning is triggered,
> > then the trace event is ignored.
> >
> > Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> > ---
> > include/linux/tracepoint.h | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> > index f72fcfe..8baef96 100644
> > --- a/include/linux/tracepoint.h
> > +++ b/include/linux/tracepoint.h
> > @@ -159,6 +159,8 @@ extern void syscall_unregfunc(void);
> > TP_PROTO(data_proto), \
> > TP_ARGS(data_args), \
> > TP_CONDITION(cond), \
> > + if (WARN_ON_ONCE(rcu_irq_enter_disabled())) \
> > + return; \
>
> I must admit that it's a bit odd to have:
>
> if (WARN_ON_ONCE(rcu_irq_enter_disabled()))
> return;
> rcu_irq_enter_irqson()
Welcome to MACRO MAGIC!
>
> as one argument to the __DO_TRACE() macro. To me it's a bit unexpected
> coding-style wise. Am I the only one not comfortable with the proposed
> syntax ?
The entire TRACE_EVENT()/__DO_TRACE() is special.
I thought about add yet another parameter, but as it doesn't change
much, I figured this was good enough. We could beak it up if you like:
#define RCU_IRQ_ENTER_CHECK \
if (WARN_ON_ONCE(rcu_irq_enter_disabled()) \
return; \
rcu_irq_enter_irqson();
[..]
__DO_TRACE(&__tracepoint_##name, \
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond), \
PARAMS(RCU_IRQ_ENTER_CHECK), \
rcu_irq_exit_irqson()); \
Would that make you feel more comfortable?
-- Steve
next prev parent reply other threads:[~2017-04-07 17:26 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-07 14:01 [PATCH 0/5 v2] tracing: Add usecase of synchronize_rcu_tasks() and stack_tracer_disable() Steven Rostedt
2017-04-07 14:01 ` [PATCH 1/5 v2] ftrace: Add use of synchronize_rcu_tasks() with dynamic trampolines Steven Rostedt
2017-04-07 14:01 ` [PATCH 2/5 v2] tracing: Replace the per_cpu() with this_cpu() in trace_stack.c Steven Rostedt
2017-04-07 14:36 ` Paul E. McKenney
2017-04-07 14:48 ` Steven Rostedt
2017-04-07 15:08 ` Paul E. McKenney
2017-04-07 14:01 ` [PATCH 3/5 v2] tracing: Add stack_tracer_disable/enable() functions Steven Rostedt
2017-04-07 14:22 ` Steven Rostedt
2017-04-07 14:25 ` [PATCH 3/5 v2.1] " Steven Rostedt
2017-04-07 14:01 ` [PATCH 4/5 v2] tracing: Rename trace_active to disable_stack_tracer and inline its modification Steven Rostedt
2017-04-07 14:01 ` [PATCH 5/5 v2] rcu: Fix dyntick-idle tracing Steven Rostedt
2017-04-07 14:40 ` Paul E. McKenney
2017-04-07 14:53 ` Steven Rostedt
2017-04-07 15:09 ` Paul E. McKenney
2017-04-07 15:29 ` Steven Rostedt
2017-04-07 14:43 ` [PATCH 0/5 v2] tracing: Add usecase of synchronize_rcu_tasks() and stack_tracer_disable() Paul E. McKenney
2017-04-07 14:58 ` Steven Rostedt
2017-04-07 15:11 ` Paul E. McKenney
2017-04-07 15:28 ` Steven Rostedt
2017-04-07 16:35 ` [PATCH 6/5]rcu/tracing: Add rcu_disabled to denote when rcu_irq_enter() will not work Steven Rostedt
2017-04-07 16:42 ` Paul E. McKenney
2017-04-07 16:44 ` Steven Rostedt
2017-04-07 16:53 ` Paul E. McKenney
2017-04-07 17:03 ` [PATCH 6/5 v2] rcu/tracing: " Steven Rostedt
2017-04-07 17:15 ` Paul E. McKenney
2017-04-07 17:06 ` [PATCH 7/5] tracing: Make sure rcu_irq_enter() can work for trace_*_rcuidle() trace events Steven Rostedt
2017-04-07 17:15 ` Paul E. McKenney
2017-04-07 17:19 ` Mathieu Desnoyers
2017-04-07 17:26 ` Steven Rostedt [this message]
2017-04-07 17:32 ` Steven Rostedt
2017-04-07 17:49 ` Mathieu Desnoyers
2017-04-07 17:55 ` Steven Rostedt
2017-04-07 18:10 ` [PATCH 7/5 v3] " Steven Rostedt
2017-04-07 18:17 ` Mathieu Desnoyers
2017-04-07 19:41 ` [PATCH 7/5 v4] " Steven Rostedt
2017-04-07 19:43 ` Steven Rostedt
2017-04-10 17:11 ` Mathieu Desnoyers
2017-04-07 17:28 ` [PATCH 7/5] " Steven Rostedt
2017-04-07 17:48 ` [PATCH 7/5 v2] " Steven Rostedt
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