Messages in this thread | | | Subject | Re: [PATCH 0/5][RFC] kprobes/ftrace: Have kprobes use ftrace on ftrace nops | From | Steven Rostedt <> | Date | Sat, 13 Aug 2011 22:58:04 -0400 |
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On Sat, 2011-08-13 at 19:09 +0900, Masami Hiramatsu wrote: > (2011/08/12 22:08), Steven Rostedt wrote: > > On Fri, 2011-08-12 at 11:57 +0900, Masami Hiramatsu wrote: > > > >> I don't think it won't work. It can work but on a long way. > >> Could you tell me your "bigger ideas"? Perhaps, we are on the different > >> way but aim to same goal. > > > > Part of the bigger ideas is to have things like function graph tracing > > use this, as it will simplify the entry.S code. There's other things > > that may come out of this too. > > Hmm, I think that the current function graph tracing implementation > is more scalable than kretprobes, because kretprobe requires > spinlock on every hit. Moreover, you can't probe NMI handler with > kprobe, and kprobes on irq-handler are also possible to fail > because of recursive-call. > So I don't recommend using kretprobe for function-graph tracer :-(
Sorry for the confusion. My idea is not to use kretprobe with function graph tracer, but to use the ftrace hooks with the pt_regs and friends for function graph tracer instead of what it does today, which is to add function graph code directly into entry.S.
The point I was making is, if I need to get ftrace function tracing being good enough for function graph tracer, then it should work with kprobes without any issues. If I need to do the work anyway (for function graph tracing) then why not use it directly with kprobes instead of doing more hooks just in the kprobe_trace?
-- Steve
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