On Tue, 7 Nov 2017 13:44:01 -0800 Linus Torvalds <torva...@linux-foundation.org> wrote:
> > Looking other places that stand out, it seems like > > /proc/lockdep_chains and /proc/lockdep (CONFIG_LOCKDEP=y) has a ton of > > %p usage. It's unclear to me if a hash is sufficient for meaningful > > debugging there? > > Maybe not, but that is also _so_ esoteric that I suspect the right fix > is to just make it root-only readable. Also note, I don't believe anyone should be running a LOCKDEP configured kernel in a production (secured) environment. As it adds quite a bit of overhead. It's something you run on test environments to make sure it doesn't detect any possible deadlocks. > > I've never used it, we should check with people who have. I get the > feeling that this is purely for PeterZ debugging. I've used it. But then again, I also debug lockdep ;-) > > The very first commit that introduced that code actually has a > > (FIXME: should go into debugfs) > > so I suspect it never should have been user-readable to begin with. I > guess it makes some things easier, but it really is *very* different > from things like profiling. Want me to whip up a patch to move the file? -- Steve > > Profiling you often *cannot* do as root - some things you profile > really shouldn't be run as root, and might even refuse to do so. So > requiring you to be root just to get a kernel profile is very bad. > > But looking at lockdep stats? Yeah, 'sudo' isn't so big of a deal. > >
