Re: [RFC][PATCH] tracing: Deprecate auto-mounting tracefs in debugfs

[Peter Zijlstra]

On Tue, Jun 17, 2025 at 01:54:46PM -0400, Steven Rostedt wrote:
> 
> 
> On June 17, 2025 1:41:07 PM EDT, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> >On Tue, Jun 17, 2025 at 01:36:14PM -0400, Steven Rostedt wrote:
> >> From: Steven Rostedt <rostedt@xxxxxxxxxxx>
> >> 
> >> In January 2015, tracefs was created to allow access to the tracing
> >> infrastructure without needing to compile in debugfs. When tracefs is
> >> configured, the directory /sys/kernel/tracing will exist and tooling is
> >> expected to use that path to access the tracing infrastructure.
> >> 
> >> To allow backward compatibility, when debugfs is mounted, it would
> >> automount tracefs in its "tracing" directory so that tooling that had hard
> >> coded /sys/kernel/debug/tracing would still work.
> >> 
> >> It has been over 10 years since the new interface was introduced, and all
> >> tooling should now be using it. Start the process of deprecating the old
> >> path so that it doesn't need to be maintained anymore.
> >
> >I've always used /debug/tracing/ (because /debug is the right place to
> >mount debugfs). You're saying this is going away and will break all my
> >scripts?!
> 
> You could mount tracefs in /tracing too:
> 
>   # mount -t tracefs nodev /tracing 
> 
> And update you scripts with a simple sed script.

If I have to edit the mount table, I'll just keep it at /debug/tracing/.
Tracing is very much debug stuff anyway. While I knew there was tracefs,
I never knew there was another mount point.

Just annoying I now have to add two entries to every new machine.. Oh
well.