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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 4483CC3815B for ; Mon, 20 Apr 2020 12:44:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1644820736 for ; Mon, 20 Apr 2020 12:44:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587386680; bh=BQw15EaX0H/tDEXPed4GXaY54eyMlZZmCdnxyv/tpqc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=pQimrq0kCXx192ZE81839ybto2w/wqxd0XXwruJ8HkE5Thx7MHBl1J7sJto47+3sh 7D0dOgf12RIqwbyZVB5+7u8Q88dgLMmUDkHZDYAPlnaijSM0XZqtPbswZixFGcsfWg cTBco3iDydjx3N6MDD4XKFEusE0DGhnXVG6w4uF0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728607AbgDTMoj (ORCPT ); Mon, 20 Apr 2020 08:44:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:38512 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728571AbgDTMoc (ORCPT ); Mon, 20 Apr 2020 08:44:32 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 C42B720735; Mon, 20 Apr 2020 12:44:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587386672; bh=BQw15EaX0H/tDEXPed4GXaY54eyMlZZmCdnxyv/tpqc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HHpwLGYo4rd1XYLYD0V4c6iQSqJBW8djbM6ptbmdyA5z78lfFGBfFKxBansv30ANj /Emi+QQyxLtmPZJmFPFZNT6iw8XXZ4LW+q5yxdr2WNvALP1OSW/C5ST2A3NDpDMJrb 2zG903qky9VKDUes8GKW2kvYDOX7JKs7oEFj/ADY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Xiao Yang , "Steven Rostedt (VMware)" Subject: [PATCH 5.6 50/71] tracing: Fix the race between registering snapshot event trigger and triggering snapshot operation Date: Mon, 20 Apr 2020 14:39:04 +0200 Message-Id: <20200420121519.286606987@linuxfoundation.org> X-Mailer: git-send-email 2.26.1 In-Reply-To: <20200420121508.491252919@linuxfoundation.org> References: <20200420121508.491252919@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Xiao Yang commit 0bbe7f719985efd9adb3454679ecef0984cb6800 upstream. Traced event can trigger 'snapshot' operation(i.e. calls snapshot_trigger() or snapshot_count_trigger()) when register_snapshot_trigger() has completed registration but doesn't allocate buffer for 'snapshot' event trigger. In the rare case, 'snapshot' operation always detects the lack of allocated buffer so make register_snapshot_trigger() allocate buffer first. trigger-snapshot.tc in kselftest reproduces the issue on slow vm: ----------------------------------------------------------- cat trace ... ftracetest-3028 [002] .... 236.784290: sched_process_fork: comm=ftracetest pid=3028 child_comm=ftracetest child_pid=3036 <...>-2875 [003] .... 240.460335: tracing_snapshot_instance_cond: *** SNAPSHOT NOT ALLOCATED *** <...>-2875 [003] .... 240.460338: tracing_snapshot_instance_cond: *** stopping trace here! *** ----------------------------------------------------------- Link: http://lkml.kernel.org/r/20200414015145.66236-1-yangx.jy@cn.fujitsu.com Cc: stable@vger.kernel.org Fixes: 93e31ffbf417a ("tracing: Add 'snapshot' event trigger command") Signed-off-by: Xiao Yang Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace_events_trigger.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -1088,14 +1088,10 @@ register_snapshot_trigger(char *glob, st struct event_trigger_data *data, struct trace_event_file *file) { - int ret = register_trigger(glob, ops, data, file); + if (tracing_alloc_snapshot_instance(file->tr) != 0) + return 0; - if (ret > 0 && tracing_alloc_snapshot_instance(file->tr) != 0) { - unregister_trigger(glob, ops, data, file); - ret = 0; - } - - return ret; + return register_trigger(glob, ops, data, file); } static int