From patchwork Wed Jan 4 21:14:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13088920 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 69C7EC46467 for ; Wed, 4 Jan 2023 21:14:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231197AbjADVOS (ORCPT ); Wed, 4 Jan 2023 16:14:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56922 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229616AbjADVOS (ORCPT ); Wed, 4 Jan 2023 16:14:18 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 723A71CB24; Wed, 4 Jan 2023 13:14:17 -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 0E43D61826; Wed, 4 Jan 2023 21:14:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 078F6C433EF; Wed, 4 Jan 2023 21:14:15 +0000 (UTC) Date: Wed, 4 Jan 2023 16:14:12 -0500 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Joel Fernandes Subject: [PATCH] tracing: Make sure trace_printk() can output as soon as it can be used Message-ID: <20230104161412.019f6c55@gandalf.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org 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. Cc: stable@vger.kernel.org Reported-by: "Joel Fernandes (Google)" Fixes: e725c731e3bb1 ("tracing: Split tracing initialization into two for early initialization") Signed-off-by: Steven Rostedt (Google) Tested-by: Joel Fernandes (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 d3005279165d..80de338f1277 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -10196,6 +10196,8 @@ void __init early_trace_init(void) static_key_enable(&tracepoint_printk_key.key); } tracer_alloc_buffers(); + + init_events(); } void __init trace_init(void) diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 900e75d96c84..11c4918ff202 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1504,6 +1504,7 @@ extern void trace_event_enable_cmd_record(bool enable); extern void trace_event_enable_tgid_record(bool enable); extern int event_trace_init(void); +extern int init_events(void); extern int event_trace_add_tracer(struct dentry *parent, struct trace_array *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 67f47ea27921..5cd4fb656306 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -1568,7 +1568,7 @@ static struct trace_event *events[] __initdata = { NULL }; -__init static int init_events(void) +__init int init_events(void) { struct trace_event *event; int i, ret; @@ -1581,4 +1581,3 @@ __init static int init_events(void) return 0; } -early_initcall(init_events);