Re: [PATCH v3] pstore/ftrace: Convert to its own enable/disable debugfs knob

[Anton Vorontsov <cbouatmailru@gmail.com>]

On Tue, Aug 21, 2012 at 09:07:19PM -0400, Steven Rostedt wrote: [...]
> I'm fine with it. I know there was some issues about recursion
> protection and I said that the function tracer now has its own
> protection where you don't need to worry about it. I was hoping that
> code would make it into 3.6, but Linus opened the merge window the day
> after I posted the final version. Which I figured was too close to the
> merge window to push for 3.6 (lots of changes occurred, and I wanted
> it vetted in linux-next for a bit).
> 
> Now those changes are queued for 3.7 and are currently in the tip
> tree.  You can supply your own temporary recursion protection to the
> function tracer callback, or wait till my changes make it into Linus's
> tree.

Great! Btw, the particular recursion issue that I faced back then was
triggered by a missing 'notrace' specifier for the ->write() callback in
pstore code, i.e. a bug in pstore.

Running without any recursion protection is prone to weird
lockups/reboots, and probably a good idea to have it on a production
system. But recursion during tracing is still an evidence of some other
bugs, right? At least the fact that I didn't have it helped me to find a
bug. So, does it make sense to make the recursion protection optionally
disabled? Maybe as some CONFIG_DEBUG_* option (briefly looking into
kernel/trace/Kconfig I didn't find any)?

Thanks,

Anton.