From patchwork Mon Apr 13 07:12:52 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xiao Yang X-Patchwork-Id: 11485193 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CCC16912 for ; Mon, 13 Apr 2020 07:26:18 +0000 (UTC) Received: from vger.kernel.org (unknown [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AD1E020774 for ; Mon, 13 Apr 2020 07:26:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AD1E020774 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=cn.fujitsu.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kselftest-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729277AbgDMH0P (ORCPT ); Mon, 13 Apr 2020 03:26:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.18]:60290 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727612AbgDMH0P (ORCPT ); Mon, 13 Apr 2020 03:26:15 -0400 Received: from heian.cn.fujitsu.com (mail.cn.fujitsu.com [183.91.158.132]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id A2657C008651; Mon, 13 Apr 2020 00:26:14 -0700 (PDT) X-IronPort-AV: E=Sophos;i="5.72,377,1580745600"; d="scan'208";a="88939532" Received: from unknown (HELO cn.fujitsu.com) ([10.167.33.5]) by heian.cn.fujitsu.com with ESMTP; 13 Apr 2020 15:26:13 +0800 Received: from G08CNEXMBPEKD04.g08.fujitsu.local (unknown [10.167.33.201]) by cn.fujitsu.com (Postfix) with ESMTP id A6AFD50A9999; Mon, 13 Apr 2020 15:15:42 +0800 (CST) Received: from G08CNEXCHPEKD02.g08.fujitsu.local (10.167.33.83) by G08CNEXMBPEKD04.g08.fujitsu.local (10.167.33.201) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 13 Apr 2020 15:26:13 +0800 Received: from Fedora-31.g08.fujitsu.local (10.167.220.31) by G08CNEXCHPEKD02.g08.fujitsu.local (10.167.33.89) with Microsoft SMTP Server id 14.3.439.0; Mon, 13 Apr 2020 15:26:09 +0800 From: Xiao Yang To: , CC: , , , Xiao Yang Subject: [PATCH] tracing: Fix the race between registering 'snapshot' event trigger and triggering 'snapshot' operation Date: Mon, 13 Apr 2020 15:12:52 +0800 Message-ID: <20200413071252.13720-1-yangx.jy@cn.fujitsu.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-yoursite-MailScanner-ID: A6AFD50A9999.ACC61 X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: yangx.jy@cn.fujitsu.com X-Spam-Status: No Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org 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 spare buffer for 'snapshot' event trigger. 'snapshot' operation always detects the lack of allocated buffer in the rare case so make register_snapshot_trigger() allocate spare 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! *** ----------------------------------------------------------- Signed-off-by: Xiao Yang --- kernel/trace/trace_events_trigger.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c index dd34a1b46a86..00e54cdcef3e 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -1088,9 +1088,13 @@ register_snapshot_trigger(char *glob, struct event_trigger_ops *ops, struct event_trigger_data *data, struct trace_event_file *file) { - int ret = register_trigger(glob, ops, data, file); + int alloc_ret, ret; - if (ret > 0 && tracing_alloc_snapshot_instance(file->tr) != 0) { + alloc_ret = tracing_alloc_snapshot_instance(file->tr); + + ret = register_trigger(glob, ops, data, file); + + if (ret > 0 && alloc_ret != 0) { unregister_trigger(glob, ops, data, file); ret = 0; }