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authorSteven Rostedt (Google) <rostedt@goodmis.org>2023-01-04 22:14:12 +0100
committerSteven Rostedt (Google) <rostedt@goodmis.org>2023-01-24 17:27:29 +0100
commit3bb06eb6e9acf7c4a3e1b5bc87aed398ff8e2253 (patch)
tree87572db01e62df0acc3101e1acb409f6050ed0c6 /kernel
parentftrace: Export ftrace_free_filter() to modules (diff)
downloadlinux-3bb06eb6e9acf7c4a3e1b5bc87aed398ff8e2253.tar.xz
linux-3bb06eb6e9acf7c4a3e1b5bc87aed398ff8e2253.zip
tracing: Make sure trace_printk() can output as soon as it can be used
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. Link: https://lkml.kernel.org/r/20230104161412.019f6c55@gandalf.local.home Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Fixes: e725c731e3bb1 ("tracing: Split tracing initialization into two for early initialization") Reported-by: "Joel Fernandes (Google)" <joel@joelfernandes.org> Tested-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace.c2
-rw-r--r--kernel/trace/trace.h1
-rw-r--r--kernel/trace/trace_output.c3
3 files changed, 4 insertions, 2 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a555a861b978..78ed5f1baa8c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -10295,6 +10295,8 @@ 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 e46a49269be2..4eb6d6b97a9f 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1490,6 +1490,7 @@ 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 57a13b61f186..bd475a00f96d 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -1535,7 +1535,7 @@ 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;
@@ -1548,4 +1548,3 @@ __init static int init_events(void)
return 0;
}
-early_initcall(init_events);