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 4A012C433F5 for ; Tue, 23 Nov 2021 08:55:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235154AbhKWI6Z (ORCPT ); Tue, 23 Nov 2021 03:58:25 -0500 Received: from smtp2.axis.com ([195.60.68.18]:55915 "EHLO smtp2.axis.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235151AbhKWI6Y (ORCPT ); Tue, 23 Nov 2021 03:58:24 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=axis.com; q=dns/txt; s=axis-central1; t=1637657717; x=1669193717; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=YY8TztApIbu8gAM/dbGhVqhWLHuckZQpbxwj+qBG80s=; b=milnxrqzSFGlJnvZYmNl7BiJq7LuEXNfslWsnIveL4cISTpK9n/Eq5qU HzH2JkdOnO0lJNVErGPVlS4R53tQFkVYyBDdS2s8QV6V6XqjV35UywS3q d2J7Om45YYJc6pNQ1Shn8LrnfRVpd3oMoNgsjiYczCCwmJmTzSGOVK2ZV HI1lL86hpP1Vy0k/saWdt9d9zczj/BbfhJ5VW0p/xkMPhLkPt3XjqdKU3 OGhJeLIpsmt5tIKn7L6tM2i7rJykf7dCOeC9L7X4aWuICO+hrkuJNjyt1 clxss4VqNhaFmJaCIFnM/GshuehHhPt3Htq3BkTevdf79IQ4p+elli+XF w==; Date: Tue, 23 Nov 2021 09:55:14 +0100 From: Vincent Whitchurch To: Steven Rostedt CC: "linux-trace-devel@vger.kernel.org" , kernel Subject: Re: [PATCH] trace-cmd report: Avoid crash on unknown event Message-ID: <20211123085514.GA12234@axis.com> References: <20211119112420.4826-1-vincent.whitchurch@axis.com> <20211119094434.718922fa@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20211119094434.718922fa@gandalf.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org On Fri, Nov 19, 2021 at 03:44:34PM +0100, Steven Rostedt wrote: > On Fri, 19 Nov 2021 12:24:20 +0100 > Vincent Whitchurch wrote: > > > Do not segfault if the event cannot be found for some reason and > > tep_find_event_by_record() returns NULL. > > > > No extra warning is added since there are others ("UNKNOWN EVENT") which > > already make it clear that something is wrong: > > > > kworker/u8:0-7 [003] 1.245773: sched_stat_runtime: comm=kworker/u8:... > > [UNKNOWN EVENT][UNKNOWN EVENT][UNKNOWN EVENT] > > kworker/u8:0-7 [003] 1.245776: sched_switch: kworker/u8:0:7 [120] W... > > > > I wonder if the following would be a better and more robust approach: > > diff --git a/tracecmd/trace-read.c b/tracecmd/trace-read.c > index f7ffb89e..4b27740a 100644 > --- a/tracecmd/trace-read.c > +++ b/tracecmd/trace-read.c > @@ -142,12 +142,15 @@ static struct trace_hash wakeup_hash; > static void print_event_name(struct trace_seq *s, struct tep_event *event) > { > static const char *spaces = " "; /* 20 spaces */ > + const char *name; > int len; > > - trace_seq_printf(s, " %s: ", event->name); > + name = event ? event->name : "(NULL)"; > + > + trace_seq_printf(s, " %s: ", name); > > /* Space out the event names evenly. */ > - len = strlen(event->name); > + len = strlen(name); > if (len < 20) > trace_seq_printf(s, "%.*s", 20 - len, spaces); > } Looks good to me.