From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A445FC5CFEB for ; Wed, 11 Jul 2018 13:00:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 54D6A208EC for ; Wed, 11 Jul 2018 13:00:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 54D6A208EC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387649AbeGKNEU (ORCPT ); Wed, 11 Jul 2018 09:04:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:42472 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732544AbeGKNEU (ORCPT ); Wed, 11 Jul 2018 09:04:20 -0400 Received: from gandalf.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D53AF2086B; Wed, 11 Jul 2018 13:00:04 +0000 (UTC) Date: Wed, 11 Jul 2018 09:00:03 -0400 From: Steven Rostedt To: Peter Zijlstra Cc: Joel Fernandes , linux-kernel@vger.kernel.org, Boqun Feng , Byungchul Park , Ingo Molnar , Julia Cartwright , linux-kselftest@vger.kernel.org, Masami Hiramatsu , Mathieu Desnoyers , Namhyung Kim , Paul McKenney , Thomas Glexiner , Tom Zanussi Subject: Re: [PATCH v9 4/7] tracepoint: Make rcuidle tracepoint callers use SRCU Message-ID: <20180711090003.42596c2b@gandalf.local.home> In-Reply-To: <20180711124954.GE2476@hirez.programming.kicks-ass.net> References: <20180628182149.226164-1-joel@joelfernandes.org> <20180628182149.226164-5-joel@joelfernandes.org> <20180711124954.GE2476@hirez.programming.kicks-ass.net> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 11 Jul 2018 14:49:54 +0200 Peter Zijlstra wrote: > On Thu, Jun 28, 2018 at 11:21:46AM -0700, Joel Fernandes wrote: > > - it_func_ptr = rcu_dereference_sched((tp)->funcs); \ > > I would convert to rcu_dereference_raw() to appease sparse. The fancy > stuff below is pointless if you then turn off all checking. The problem with doing this is if we use a trace event without the proper _idle() or whatever, we wont get a warning that it is used incorrectly with lockdep. Or does lockdep still check if "rcu is watching" with rcu_dereference_raw()? -- Steve > > > + \ > > + /* \ > > + * For rcuidle callers, use srcu since sched-rcu \ > > + * doesn't work from the idle path. \ > > + */ \ > > + if (rcuidle) { \ > > + if (in_nmi()) { \ > > + WARN_ON_ONCE(1); \ > > + return; /* no srcu from nmi */ \ > > + } \ > > + \ > > + idx = srcu_read_lock_notrace(&tracepoint_srcu); \ > > + it_func_ptr = \ > > + srcu_dereference_notrace((tp)->funcs, \ > > + &tracepoint_srcu); \ > > + /* To keep it consistent with !rcuidle path */ \ > > + preempt_disable_notrace(); \ > > + } else { \ > > + rcu_read_lock_sched_notrace(); \ > > + it_func_ptr = \ > > + rcu_dereference_sched((tp)->funcs); \ > > + } \