Re: ftrace and debugfs weird interaction

[Ingo Molnar <mingo@elte.hu>]

* Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:

> Hi,
> 
> When trying to figure out what was going on with the sched tracer
> "tracing_enabled" file (sched-devel.git tree), I fell on this strange
> behavior :
> 
> echo 1>tracing_enabled seems _not_ to send 1 to the tracing_ctrl_write
> callback. However, sending garbage, e.g. echo s> tracing_enabled,
> correctly sends the 's' character down the chain. echo 0>tracing_enabled
> sometimes results in the callback not even being called.
> 
> The debugfs file has been created with
> 
>         entry = debugfs_create_file("tracing_enabled", 0644, d_tracer,
>                                     &global_trace, &tracing_ctrl_fops);
>         if (!entry)
>                 pr_warning("Could not create debugfs 'tracing_enabled' entry\n");
> 
> I wonder what kind of weird debugfs interaction we might have here ?

hm. Cc:-ed more ftrace developers.

	Ingo