Re: [PATCH 3/5] tracing/ftrace: check if debugfs is registeredbefore creating files

[Ingo Molnar]

* Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:

> Impact: fix a crash with ftrace={nop,boot} parameter
> 
> If the nop or initcall tracers are launched as boot tracers,
> they will attempt to create their option directory and files.
> But these tracers are registered very early and then assigned
> as "boot tracers" very early if asked to.
> 
> Since they do this before debugfs has been registered (core initcall),
> a crash is triggered.
> 
> Another early tracers could also come later. So we fix it by
> checking if debugfs is initialized before creating the root
> tracing directory.
> 
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxx>
> Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> ---
>  kernel/trace/trace.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)

Note - i'll delay this patch pending Greg's Ack.

	Ingo
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