From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934486AbdDGRSC (ORCPT ); Fri, 7 Apr 2017 13:18:02 -0400 Received: from mail.efficios.com ([167.114.142.141]:55977 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933502AbdDGRR4 (ORCPT ); Fri, 7 Apr 2017 13:17:56 -0400 Date: Fri, 7 Apr 2017 17:19:05 +0000 (UTC) From: Mathieu Desnoyers To: rostedt Cc: linux-kernel , Ingo Molnar , Andrew Morton , "Paul E. McKenney" Message-ID: <1475342880.4473.1491585545139.JavaMail.zimbra@efficios.com> In-Reply-To: <20170407130615.2309b96d@gandalf.local.home> References: <20170407140106.051135969@goodmis.org> <20170407130615.2309b96d@gandalf.local.home> Subject: Re: [PATCH 7/5] tracing: Make sure rcu_irq_enter() can work for trace_*_rcuidle() trace events MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.142.141] X-Mailer: Zimbra 8.7.6_GA_1776 (ZimbraWebClient - FF45 (Linux)/8.7.6_GA_1776) Thread-Topic: tracing: Make sure rcu_irq_enter() can work for trace_*_rcuidle() trace events Thread-Index: tgthSxxpKweKAe63A5AQobnXcsCHIA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- On Apr 7, 2017, at 1:06 PM, rostedt rostedt@goodmis.org wrote: > From: "Steven Rostedt (VMware)" > > 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 Do you have a link to the lkml thread where this stack tracing discovery happened ? > 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 > Signed-off-by: Steven Rostedt (VMware) > --- > 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() 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 ? Thanks, Mathieu > rcu_irq_enter_irqson(), \ > rcu_irq_exit_irqson()); \ > } > -- > 2.9.3 -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com