From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 F341B3229 for ; Mon, 30 Jan 2023 14:24:52 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 59030C433EF; Mon, 30 Jan 2023 14:24:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1675088692; bh=xyfc8lTCVMvnK7t/kwr12+yqcFAAvsnSl1Jn034eCQs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=koh8sk8TEWP9ojv5BTCMmYbD/2qyB31XF6Nzos4DyfIKmgqhax4UXXycB/CUezBwt q8iNDWXj+NGpx5RHvpEhdSk4X/EdBwKmt29aL1McLmLHwZpTaSEzonpEMFwjnFl3w+ D4SkiXS0XqsDAL8YVD6FV2c1dbrcyV+70piZr/Ho= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Masami Hiramatsu , "Joel Fernandes (Google)" , "Steven Rostedt (Google)" Subject: [PATCH 5.10 103/143] tracing: Make sure trace_printk() can output as soon as it can be used Date: Mon, 30 Jan 2023 14:52:40 +0100 Message-Id: <20230130134311.121327994@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230130134306.862721518@linuxfoundation.org> References: <20230130134306.862721518@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Steven Rostedt (Google) commit 3bb06eb6e9acf7c4a3e1b5bc87aed398ff8e2253 upstream. 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 early initialization") Reported-by: "Joel Fernandes (Google)" Tested-by: Joel Fernandes (Google) Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace.c | 2 ++ kernel/trace/trace.h | 1 + kernel/trace/trace_output.c | 3 +-- 3 files changed, 4 insertions(+), 2 deletions(-) --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -9680,6 +9680,8 @@ void __init early_trace_init(void) static_key_enable(&tracepoint_printk_key.key); } tracer_alloc_buffers(); + + init_events(); } void __init trace_init(void) --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1673,6 +1673,7 @@ extern void trace_event_enable_cmd_recor 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); --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -1378,7 +1378,7 @@ static struct trace_event *events[] __in NULL }; -__init static int init_events(void) +__init int init_events(void) { struct trace_event *event; int i, ret; @@ -1396,4 +1396,3 @@ __init static int init_events(void) return 0; } -early_initcall(init_events);