On Thu, 3 Jul 2014, Steven Rostedt wrote: > [ NOT READY FOR INCLUSION! ] > > Note, this is based off of my remove ftrace_start/stop() patch set. > > I've been wanting to do this for years, and just never gotten around to it. > But with all this talk of kpatch and kgraft live kernel patching using > the ftrace infrastructure, it seems like a good time to do it. > > The way the function callback mechanism works in ftrace is that if there's > only one function callback registered, it will set the mcount/fentry > trampoline to call that function directly. But as soon as you register > another callback, the mcount trampoline calls a loop function that iterates > over all the registered callbacks (ftrace_ops) checking their hash tables > to see if the called function matches the ops before calling its callback. > This happens even if the two registered functions are not even tracing > the same function! > > This really sucks if you are tracing all functions, and then add a kprobe > or perf event that traces a single function. That will cause all the > other functions being traced to perform the loop test. [ ... snip ... ]
For the record -- I just did a quick test, and kGraft works nicely on top of this patchset. Will be looking into the patches more closely later this week. -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/