On 11/12/21 12:07 PM, Steven Rostedt wrote:

On Fri, 12 Nov 2021 10:08:41 -0500
Jason Baron [off-list ref] wrote:

quoted

quoted

A key difference between that patchset and this patch (besides that
small fact that I used +x instead of +T) was that my patchset allowed
the dyndbg trace to be emitted to the main buffer and did not force them
to be in an instance-specific buffer.  

Yes, I agree I'd prefer that we print here to the 'main' buffer - it seems to keep things simpler and easier to combine the output from different
sources as you mentioned.

I do not want anything to print to the "main buffer" that can not be
filtered or turned off by the tracing infrastructure itself (aka tracefs
file system).

Once we allow that, then the trace file will become useless because
everything will write to the main buffer and fill it with noise.

Events that can be enabled and disabled from tracefs are fine, as they can
be limited. This is why I added that nasty warning if people leave around
trace_printk(), because it does exactly this (write to the main buffer).
It's fine for debugging a custom kernel, but should never be enabled in
something that is shipped, or part of mainline.

-- Steve

Ok, it looks like Vincent's patch defines a dyndbg event and then uses
'trace_dyndbg()' to output to the 'main' log. So all dynamic output to
the 'main' ftrace buffer goes through that event if I understand it
correctly. Here's a pointer to it for reference:

https://lore.kernel.org/lkml/20200825153338.17061-3-vincent.whitchurch@axis.com/ (local)

Would you be ok with that approach?

Thanks,

-Jason


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