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 AA5231FB4 for ; Fri, 3 Feb 2023 10:19:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2B4EAC433D2; Fri, 3 Feb 2023 10:19:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1675419548; bh=1UN+gLZSx+eaHZf/XZJuq69ynRwqJLTS/UB3V6P0mdY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EXX4nbzxFSZXfN0/0lq2P2uOPXJ55zJVvhLPbMr9U3H0FSCDr4HItE7fNaRkm+wDd wyk7RDIWjnuVCGcxODgTNBhmlmp5IAEdtW39NXMMjgngObnfIFp7fcg6/PeC5FVuXt OQVU7R4irg/lY/RvWDm1eMh7tVzmde6vCoIUZRCI= 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 4.19 39/80] tracing: Make sure trace_printk() can output as soon as it can be used Date: Fri, 3 Feb 2023 11:12:33 +0100 Message-Id: <20230203101016.853819527@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230203101015.263854890@linuxfoundation.org> References: <20230203101015.263854890@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 @@ -8674,6 +8674,8 @@ 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 @@ -1530,6 +1530,7 @@ 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); --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -1395,7 +1395,7 @@ 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; @@ -1413,4 +1413,3 @@ __init static int init_events(void) return 0; } -early_initcall(init_events);