linux-kernel - [for-next][PATCH 23/26] tracing: Enable adding dynamic events early stage

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Message-ID: <20200922012453.360307617@goodmis.org>
Date:   Mon, 21 Sep 2020 21:24:37 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: [for-next][PATCH 23/26] tracing: Enable adding dynamic events early stage

From: Masami Hiramatsu <mhiramat@...nel.org>

Split the event fields initialization from creating new event directory.
This allows the boot-time tracing to define dynamic events before
initializing events directory on tracefs.

Link: https://lkml.kernel.org/r/159974153790.478751.3475515065034825374.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/trace/trace_events.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 8e87fbab6930..42c0e7df6e70 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -38,6 +38,7 @@ DEFINE_MUTEX(event_mutex);
 LIST_HEAD(ftrace_events);
 static LIST_HEAD(ftrace_generic_fields);
 static LIST_HEAD(ftrace_common_fields);
+static bool eventdir_initialized;
 
 #define GFP_TRACE (GFP_KERNEL | __GFP_ZERO)
 
@@ -2486,7 +2487,10 @@ __trace_add_new_event(struct trace_event_call *call, struct trace_array *tr)
 	if (!file)
 		return -ENOMEM;
 
-	return event_create_dir(tr->event_dir, file);
+	if (eventdir_initialized)
+		return event_create_dir(tr->event_dir, file);
+	else
+		return event_define_fields(call);
 }
 
 /*
@@ -3478,6 +3482,9 @@ __init int event_trace_init(void)
 	if (ret)
 		pr_warn("Failed to register trace events module notifier\n");
 #endif
+
+	eventdir_initialized = true;
+
 	return 0;
 }
 
-- 
2.28.0