From nobody Sun Sep 14 10:04:21 2025 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 95A0DC61D97 for ; Wed, 25 Jan 2023 16:20:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235743AbjAYQUP (ORCPT ); Wed, 25 Jan 2023 11:20:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52256 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230089AbjAYQUN (ORCPT ); Wed, 25 Jan 2023 11:20:13 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 37F4055285; Wed, 25 Jan 2023 08:20:12 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C135E61226; Wed, 25 Jan 2023 16:20:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 37CC1C433A0; Wed, 25 Jan 2023 16:20:11 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.96) (envelope-from ) id 1pKiVO-004Mqq-0e; Wed, 25 Jan 2023 11:20:10 -0500 Message-ID: <20230125162010.016206071@goodmis.org> User-Agent: quilt/0.66 Date: Wed, 25 Jan 2023 11:18:26 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Andrew Morton , stable@vger.kernel.org, "Joel Fernandes (Google)" Subject: [for-linus][PATCH 02/11] tracing: Make sure trace_printk() can output as soon as it can be used References: <20230125161824.332648375@goodmis.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: "Steven Rostedt (Google)" Currently trace_printk() can be used as soon as early_trace_init() is called from start_kernel(). But if a crash happens, and "ftrace_dump_on_oops" is set on the kernel command line, all you get will be: [ 0.456075] -0 0dN.2. 347519us : Unknown type 6 [ 0.456075] -0 0dN.2. 353141us : Unknown type 6 [ 0.456075] -0 0dN.2. 358684us : Unknown type 6 This is because the trace_printk() event (type 6) hasn't been registered yet. That gets done via an early_initcall(), which may be early, but not early enough. Instead of registering the trace_printk() event (and other ftrace events, which are not trace events) via an early_initcall(), have them registered at the same time that trace_printk() can be used. This way, if there is a crash before early_initcall(), then the trace_printk()s will actually be useful. Link: https://lkml.kernel.org/r/20230104161412.019f6c55@gandalf.local.home Cc: stable@vger.kernel.org Cc: Masami Hiramatsu Fixes: e725c731e3bb1 ("tracing: Split tracing initialization into two for e= arly initialization") Reported-by: "Joel Fernandes (Google)" Tested-by: Joel Fernandes (Google) Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace.c | 2 ++ kernel/trace/trace.h | 1 + kernel/trace/trace_output.c | 3 +-- 3 files changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index a555a861b978..78ed5f1baa8c 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -10295,6 +10295,8 @@ void __init early_trace_init(void) static_key_enable(&tracepoint_printk_key.key); } tracer_alloc_buffers(); + + init_events(); } =20 void __init trace_init(void) diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index e46a49269be2..4eb6d6b97a9f 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1490,6 +1490,7 @@ extern void trace_event_enable_cmd_record(bool enable= ); extern void trace_event_enable_tgid_record(bool enable); =20 extern int event_trace_init(void); +extern int init_events(void); extern int event_trace_add_tracer(struct dentry *parent, struct trace_arra= y *tr); extern int event_trace_del_tracer(struct trace_array *tr); extern void __trace_early_add_events(struct trace_array *tr); diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 57a13b61f186..bd475a00f96d 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -1535,7 +1535,7 @@ static struct trace_event *events[] __initdata =3D { NULL }; =20 -__init static int init_events(void) +__init int init_events(void) { struct trace_event *event; int i, ret; @@ -1548,4 +1548,3 @@ __init static int init_events(void) =20 return 0; } -early_initcall(init_events); --=20 2.39.0