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/[email protected]

Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Fixes: e725c731e3bb1 ("tracing: Split tracing initialization into two for early initialization")
Reported-by: "Joel Fernandes (Google)" <[email protected]>
Tested-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

0 files changed, 0 insertions, 0 deletions