Messages in this thread | | | From | Saravana Kannan <> | Date | Mon, 27 Jan 2020 14:19:34 -0800 | Subject | Re: [PATCH v3] dynamic_debug: allow to work if debugfs is disabled |
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On Sat, Jan 25, 2020 at 9:11 AM Jonathan Corbet <corbet@lwn.net> wrote: > > On Fri, 24 Jan 2020 20:42:31 -0500 > "Theodore Y. Ts'o" <tytso@mit.edu> wrote: > > > On Fri, Jan 24, 2020 at 08:29:40AM +0100, Greg Kroah-Hartman wrote: > > > > It's likely that people who normally use > > > > distribution kernels where debugfs is disabled will have scripts which > > > > are hard-coded to look in /proc, and then when they build a kernel > > > > with debugfs enabled, the /proc entry will go **poof**, and their > > > > script will break. > > > > > > **poof** they didn't test it :) > > > > > > Seriously, I am doing this change to make it _easier_ for those people > > > who want debugfs disabled, yet want this type of debugging. This is > > > much better than having no debugging at all. > > > > > > Don't put extra complexity in the kernel for when it can be trivially > > > handled in userspace, you know this :) > > > > It's also trivial to handle this in the kernel by potentially having > > the control file appear in two places. Consider what it would be like > > to explain this in the Linux documentation --- "the control file could > > be here, or it could be there", depending on how the kernel is > > configured. The complexity of documenting this, and the complexity in > > userspace; and we have to have the code in the source code for the > > file to be in the appear in both places *anyway*. > > FWIW, avoiding the need to document something like this has been a > motivating factor behind a number of my patches over the years. > > Moving a control knob based on kernel configuration is a user-hostile > feature. Scripts can be made to cope with this kind of behavior in one > place; if you let such things accumulate in a system, though, it gets to > the point where it's really hard for anybody to keep track of all the > pieces and be sure that their code will work. > > If dynamic debug is meant to be a feature supported on all kernels, it > should, IMO, be lifted out of debugfs and made into a proper feature - with > a compatibility link left behind in debugfs for as long as it's needed, of > course. > > </sermon> :)
My 2 cents -- agree with what Ted and Jon have said.
-Saravana
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