From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 134B042122D; Thu, 6 Aug 2026 21:41:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.13 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786052475; cv=none; b=l1yw5M5EjXZ0d0hbqPcBxWHJ7629DH4GZJrs/7PSpP+PFtgfYNGxRDObknOxlBO1lfCWObZvMdxK3weV9y8+t8yL0qCmZCR3JGZpeZY9vAIK7cgJNpw7FsySPBYdOWjpBsIp8XWGfiLe7yHhm+wQOPqZGkclX7PMqzkGB1Vd9lw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786052475; c=relaxed/simple; bh=2059UvzVy2fTJZSkXT5cmIeP0B0YcuicIhxl4ZM5ns0=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=W8zqSwnGVPjuTGGFo4PhL0WJbse7o18OyPi+I34lHhUl2j3FPY8pmJY/Nbls32zpsU8v1NivW//9chx6yqGfRbrrccOfxSypP2bkB8RVS9qsrbyRgHWoa8+s2QUFPcnWBeV0xDogsIPrtISqjJ1MZz47e1rS5deRwkrwSsDUp28= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.13 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf11.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 9BB4740302; Thu, 6 Aug 2026 21:41:11 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf11.hostedemail.com (Postfix) with ESMTPA id C3A7C20029; Thu, 6 Aug 2026 21:41:09 +0000 (UTC) Date: Thu, 6 Aug 2026 17:41:10 -0400 From: Steven Rostedt To: David Carlier Cc: Masami Hiramatsu , Mathieu Desnoyers , linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] tracing: Report TP_printk double dereference with pr_warn() Message-ID: <20260806174110.11fcd317@gandalf.local.home> In-Reply-To: <20260806050716.16612-1-devnexen@gmail.com> References: <20260806050716.16612-1-devnexen@gmail.com> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: a66kyw4fw5bzrdz9fzf4n4imkqj4wdgj X-Rspamd-Server: rspamout08 X-Rspamd-Queue-Id: C3A7C20029 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1/Vd6dPW2F+9+BGdpcfnNhllw5pYGLi+Ks= X-HE-Tag: 1786052469-122285 X-HE-Meta: U2FsdGVkX1875b5qojOzgagTvgfJ1QN95Ien6dv+qKL9nrocqKufPaILFYTXI/QN34W9NtKDy65+RlNX5Ui3eZd8ZCjh8iv3KTgfbgXIaFAJpGQEjHXANTFmEfMGmlfw6O07KaBb66xtCbnLBEHUPwvcFD5F836LLJH81w0ihPKrVOS6D43RcFEKJxKQM92XsYEmGYzm8i7/Eg8GJUtVZNHJFoHi6A8VNJ1vKphmFxO7kRH5N7MfiZk4C26kQGB4VQstBcqoD0mnUrlrcsRa4LE3e5gX+4N+5luOmFuDVQdemCoMtkqhfevWZcI3t4Z+UOHv1UvEtBWLcR0urERDP+xH3GYOKugO On Thu, 6 Aug 2026 06:07:16 +0100 David Carlier wrote: > test_double_dereference() uses WARN_ONCE(), which is per-call-site. Only > the first offending event in the kernel is ever reported, and the tree > still has six: ice_{rx,tx}_dim_template, two hfi1 txq events, mtu3_ep and > edma_log_io. Whichever registers first hides the rest, and it taints the > kernel for what is a source-level mistake. > > Use pr_warn() instead, matching the "TRACE EVENT ERROR:" report that > handle_dereference_arg() already emits for the same class of problem. > All offenders are now listed on one boot. NAK! > > Fixes: b5cc230af5e5 ("tracing: Warn when an event dereferences a pointer in TP_printk()") This is by no way a fix! I want a big splat when this is triggered. It is a bug and needs to be fixed immediately. pr_warn() does not make tests fail. I want this to fail tests. I want this to panic when panic_on_warn is set. > Signed-off-by: David Carlier > --- > 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 a8590d2394e3..53f32752edc0 100644 > --- a/kernel/trace/trace_events.c > +++ b/kernel/trace/trace_events.c > @@ -415,8 +415,8 @@ static void test_double_dereference(const char *str, int len, > ptr += 5; > for (; ptr < end; ptr++) { > if (ptr[0] == '-' && ptr[1] == '>') { > - WARN_ONCE(1, "Event %s has double dereference in TP_printk: %.*s\n", > - trace_event_name(call), len, str); > + pr_warn("TRACE EVENT ERROR: Event %s has double dereference in TP_printk: %.*s\n", > + trace_event_name(call), len, str); Now I am OK with adding a pr_warn() with the WARN_ONCE() but the WARN_ONCE() must stay. But leave off the fixes tag. -- Steve > return; > } > if (!isalnum(*ptr) && *ptr != '_')