Re: [PATCH v10 08/10] dyndbg: add print-to-tracefs, selftest with it - RFC

[Vincent Whitchurch]

On Fri, Nov 19, 2021 at 11:46:31PM +0100, jim.cromie@xxxxxxxxx wrote:
> Vincent's code has the macro magic to define that event, which IIUC
> is what  makes it controllable by ftrace, and therefore acceptable in
> principle to Steve.
> Would there be any reason to expand his set of 2 events into dev_dbg,
> pr_debug etc varieties ?
> (ie any value to separating dev, !dev ?, maybe so
> 
> Sean's code uses trace_array_printk primarily, which is EXPORTed,
> which is a virtue.
> 
> Vincents code does
> +/*
> + * This code is heavily based on __ftrace_trace_stack().
> + *
> + * Allow 4 levels of nesting: normal, softirq, irq, NMI.
> + */
> 
> to implement
> 
> +static void dynamic_trace(const char *fmt, va_list args)
> 
> Has this __ftrace_trace_stack() code been bundled into or hidden under
> a supported interface ?
> 
> would it look anything like trace_array_printk() ?
> 
> what problem is that code solving inside dynamic-debug.c ?

I'm not sure I fully understand all of your questions, but perhaps this
thread with Steven's reply to the first version of my patchset will
answer some of them:

 https://lore.kernel.org/lkml/20200723112644.7759f82f@xxxxxxxxxxxxxxxx/