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=-1.0 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 2C162C46460 for ; Sat, 11 Aug 2018 13:50:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CF38E217AE for ; Sat, 11 Aug 2018 13:50:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CF38E217AE 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 S1727821AbeHKQYd (ORCPT ); Sat, 11 Aug 2018 12:24:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:39986 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727627AbeHKQYc (ORCPT ); Sat, 11 Aug 2018 12:24:32 -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 C1E9E21A2B; Sat, 11 Aug 2018 13:50:16 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.91) (envelope-from ) id 1foUHX-0006Di-Qs; Sat, 11 Aug 2018 09:50:15 -0400 Message-Id: <20180811135015.738126021@goodmis.org> User-Agent: quilt/0.65 Date: Sat, 11 Aug 2018 09:49:54 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Masami Hiramatsu , "Joel Fernandes (Google)" Subject: [for-next][PATCH 26/34] trace: Use rcu_dereference_raw for hooks from trace-event subsystem References: <20180811134928.034373761@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Joel Fernandes (Google)" Since we switched to using SRCU for tracepoints used in the idle path, we can no longer use rcu_dereference_sched for dereferencing points in trace-event hooks. Since tracepoints can now use either SRCU or sched-RCU, just use rcu_dereference_raw for traceevents just like we're doing when dereferencing the tracepoint table. This prevents an RCU warning reported by Masami: [ 282.060593] WARNING: can't dereference registers at 00000000f3c7f62b [ 282.063200] ============================= [ 282.064082] WARNING: suspicious RCU usage [ 282.064963] 4.18.0-rc6+ #15 Tainted: G W [ 282.066048] ----------------------------- [ 282.066923] /home/mhiramat/ksrc/linux/kernel/trace/trace_events.c:242 suspicious rcu_dereference_check() usage! [ 282.068974] [ 282.068974] other info that might help us debug this: [ 282.068974] [ 282.070770] [ 282.070770] RCU used illegally from idle CPU! [ 282.070770] rcu_scheduler_active = 2, debug_locks = 1 [ 282.072938] RCU used illegally from extended quiescent state! [ 282.074183] no locks held by swapper/0/0. [ 282.075071] [ 282.075071] stack backtrace: [ 282.076121] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W [ 282.077782] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) [ 282.079604] Call Trace: [ 282.080212] [ 282.080755] dump_stack+0x85/0xcb [ 282.081523] trace_event_ignore_this_pid+0x66/0x70 [ 282.082541] trace_event_raw_event_preemptirq_template+0xa2/0xb0 [ 282.083774] ? interrupt_entry+0xc4/0xe0 [ 282.084665] ? trace_hardirqs_off_thunk+0x1a/0x1c [ 282.085669] trace_hardirqs_off_caller+0x90/0xd0 [ 282.086597] trace_hardirqs_off_thunk+0x1a/0x1c [ 282.087433] ? call_function_interrupt+0xa/0x20 [ 282.088201] interrupt_entry+0xc4/0xe0 [ 282.088848] ? call_function_interrupt+0xa/0x20 [ 282.089579] [ 282.090029] ? native_safe_halt+0x2/0x10 [ 282.090695] ? default_idle+0x1f/0x160 [ 282.091330] ? default_idle_call+0x24/0x40 [ 282.091997] ? do_idle+0x210/0x250 [ 282.092658] ? cpu_startup_entry+0x6f/0x80 [ 282.093338] ? start_kernel+0x49d/0x4bd [ 282.093987] ? secondary_startup_64+0xa5/0xb0 Link: http://lkml.kernel.org/r/20180803023407.225852-1-joel@joelfernandes.org Reported-by: Masami Hiramatsu Tested-by: Masami Hiramatsu Fixes: e6753f23d961 ("tracepoint: Make rcuidle tracepoint callers use SRCU") Signed-off-by: Joel Fernandes (Google) Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_events.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 14ff4ff3caab..7b508ce8ac44 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -239,7 +239,7 @@ bool trace_event_ignore_this_pid(struct trace_event_file *trace_file) struct trace_array_cpu *data; struct trace_pid_list *pid_list; - pid_list = rcu_dereference_sched(tr->filtered_pids); + pid_list = rcu_dereference_raw(tr->filtered_pids); if (!pid_list) return false; @@ -512,7 +512,7 @@ event_filter_pid_sched_process_exit(void *data, struct task_struct *task) struct trace_pid_list *pid_list; struct trace_array *tr = data; - pid_list = rcu_dereference_sched(tr->filtered_pids); + pid_list = rcu_dereference_raw(tr->filtered_pids); trace_filter_add_remove_task(pid_list, NULL, task); } -- 2.18.0