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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EBA33C433F5 for ; Wed, 9 Mar 2022 13:13:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232373AbiCINOR convert rfc822-to-8bit (ORCPT ); Wed, 9 Mar 2022 08:14:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55518 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233016AbiCINOQ (ORCPT ); Wed, 9 Mar 2022 08:14:16 -0500 Received: from us-smtp-delivery-44.mimecast.com (us-smtp-delivery-44.mimecast.com [205.139.111.44]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 5AE6410A7DF for ; Wed, 9 Mar 2022 05:13:18 -0800 (PST) Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-256-ySWuyVfmPTaf810awxiH3A-1; Wed, 09 Mar 2022 08:13:14 -0500 X-MC-Unique: ySWuyVfmPTaf810awxiH3A-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DB66151DC; Wed, 9 Mar 2022 13:13:12 +0000 (UTC) Received: from x1.com (unknown [10.22.8.180]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2E77D22E11; Wed, 9 Mar 2022 13:13:05 +0000 (UTC) From: Daniel Bristot de Oliveira To: Steven Rostedt Cc: Daniel Bristot de Oliveira , linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org, Marcelo Tosatti , Ingo Molnar , Nicolas Saenz Julienne Subject: [PATCH] tracing/osnoise: Do not unregister events twice Date: Wed, 9 Mar 2022 14:13:02 +0100 Message-Id: <938765e17d5a781c2df429a98f0b2e7cc317b022.1646823913.git.bristot@kernel.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kernel.org Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset=WINDOWS-1252 Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org Nicolas reported that using: # trace-cmd record -e all -M 10 -p osnoise --poll Resulted in the following kernel warning: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 1217 at kernel/tracepoint.c:404 tracepoint_probe_unregister+0x280/0x370 [...] CPU: 0 PID: 1217 Comm: trace-cmd Not tainted 5.17.0-rc6-next-20220307-nico+ #19 RIP: 0010:tracepoint_probe_unregister+0x280/0x370 [...] CR2: 00007ff919b29497 CR3: 0000000109da4005 CR4: 0000000000170ef0 Call Trace: osnoise_workload_stop+0x36/0x90 tracing_set_tracer+0x108/0x260 tracing_set_trace_write+0x94/0xd0 ? __check_object_size.part.0+0x10a/0x150 ? selinux_file_permission+0x104/0x150 vfs_write+0xb5/0x290 ksys_write+0x5f/0xe0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7ff919a18127 [...] ---[ end trace 0000000000000000 ]--- The warning complains about an attempt to unregister an unregistered tracepoint. This happens on trace-cmd because it first stops tracing, and then switches the tracer to nop. Which is equivalent to: # cd /sys/kernel/tracing/ # echo osnoise > current_tracer # echo 0 > tracing_on # echo nop > current_tracer The osnoise tracer stops the workload when no trace instance is actually collecting data. This can be caused both by disabling tracing or disabling the tracer itself. To avoid unregistering events twice, use the existing trace_osnoise_callback_enabled variable to check if the events (and the workload) are actually active before trying to deactivate them. Cc: Steven Rostedt Cc: Daniel Bristot de Oliveira Cc: Ingo Molnar Cc: Nicolas Saenz Julienne Fixes: 2fac8d6486d5 ("tracing/osnoise: Allow multiple instances of the same tracer") Reported-by: Nicolas Saenz Julienne Signed-off-by: Daniel Bristot de Oliveira --- kernel/trace/trace_osnoise.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c index cfddb30e65ab..c9eb5001e5cb 100644 --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -2200,6 +2200,17 @@ static void osnoise_workload_stop(void) if (osnoise_has_registered_instances()) return; + /* + * If callbacks were already disabled in a previous stop + * call, there is no need to disable then again. + * + * For instance, this happens when tracing is stopped via: + * echo 0 > tracing_on + * echo nop > current_tracer. + */ + if (!trace_osnoise_callback_enabled) + return; + trace_osnoise_callback_enabled = false; /* * Make sure that ftrace_nmi_enter/exit() see -- 2.34.1