Messages in this thread Patch in this message | | | Date | Wed, 4 Jan 2023 16:14:12 -0500 | From | Steven Rostedt <> | Subject | [PATCH] tracing: Make sure trace_printk() can output as soon as it can be used |
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From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
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] <idle>-0 0dN.2. 347519us : Unknown type 6 [ 0.456075] <idle>-0 0dN.2. 353141us : Unknown type 6 [ 0.456075] <idle>-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)" <joel@joelfernandes.org> Fixes: e725c731e3bb1 ("tracing: Split tracing initialization into two for early initialization") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> --- 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); -- 2.35.1
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