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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 A41F3C33C9E for ; Tue, 14 Jan 2020 22:11:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 72C2D24656 for ; Tue, 14 Jan 2020 22:11:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728774AbgANWLd (ORCPT ); Tue, 14 Jan 2020 17:11:33 -0500 Received: from mail.kernel.org ([198.145.29.99]:50556 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726491AbgANWLd (ORCPT ); Tue, 14 Jan 2020 17:11:33 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (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 6EECB24656; Tue, 14 Jan 2020 22:11:32 +0000 (UTC) Date: Tue, 14 Jan 2020 17:11:31 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Tom Zanussi , Masami Hiramatsu Subject: Re: [for-next][PATCH 26/26] tracing: trigger: Replace unneeded RCU-list traversals Message-ID: <20200114171131.04eff860@gandalf.local.home> In-Reply-To: <20200114210339.492724604@goodmis.org> References: <20200114210316.450821675@goodmis.org> <20200114210339.492724604@goodmis.org> X-Mailer: Claws Mail 3.17.3 (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 Tue, 14 Jan 2020 16:03:42 -0500 Steven Rostedt wrote: > From: Masami Hiramatsu > > With CONFIG_PROVE_RCU_LIST, I had many suspicious RCU warnings > when I ran ftracetest trigger testcases. > > ----- > # dmesg -c > /dev/null > # ./ftracetest test.d/trigger > ... > # dmesg | grep "RCU-list traversed" | cut -f 2 -d ] | cut -f 2 -d " " > kernel/trace/trace_events_hist.c:6070 > kernel/trace/trace_events_hist.c:1760 > kernel/trace/trace_events_hist.c:5911 > kernel/trace/trace_events_trigger.c:504 > kernel/trace/trace_events_hist.c:1810 > kernel/trace/trace_events_hist.c:3158 > kernel/trace/trace_events_hist.c:3105 > kernel/trace/trace_events_hist.c:5518 > kernel/trace/trace_events_hist.c:5998 > kernel/trace/trace_events_hist.c:6019 > kernel/trace/trace_events_hist.c:6044 > kernel/trace/trace_events_trigger.c:1500 > kernel/trace/trace_events_trigger.c:1540 > kernel/trace/trace_events_trigger.c:539 > kernel/trace/trace_events_trigger.c:584 > ----- > > I investigated those warnings and found that the RCU-list > traversals in event trigger and hist didn't need to use > RCU version because those were called only under event_mutex. > > I also checked other RCU-list traversals related to event > trigger list, and found that most of them were called from > event_hist_trigger_func() or hist_unregister_trigger() or > register/unregister functions except for a few cases. > > Replace these unneeded RCU-list traversals with normal list > traversal macro and lockdep_assert_held() to check the > event_mutex is held. > > Link: http://lkml.kernel.org/r/157680910305.11685.15110237954275915782.stgit@devnote2 > > Reviewed-by: Tom Zanussi > Signed-off-by: Masami Hiramatsu > Signed-off-by: Steven Rostedt (VMware) > --- > kernel/trace/trace_events_hist.c | 41 +++++++++++++++++++++-------- > kernel/trace/trace_events_trigger.c | 20 ++++++++++---- > 2 files changed, 45 insertions(+), 16 deletions(-) > I think I may add this to my urgent branch and mark this for stable. -- Steve