ftrace and debugfs weird interaction

[Mathieu Desnoyers]

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 ?

Mathieu

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Mathieu Desnoyers
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