Messages in this thread | | | Date | Mon, 08 Jul 2013 11:36:47 +0900 | From | Masami Hiramatsu <> | Subject | Re: [RFC][PATCH 3/4] tracing/kprobes: Fail to unregister if probe event files are open |
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(2013/07/06 2:26), Oleg Nesterov wrote: > On 07/05, Masami Hiramatsu wrote: >> >> (2013/07/05 3:48), Oleg Nesterov wrote: >>> On 07/04, Masami Hiramatsu wrote: >>>> >>>> Actually disable_kprobe() doesn't ensure to finish the current running >>>> kprobe handlers. >>> >>> Yes. in fact disable_trace_probe(file != NULL) does, but perf doesn't. >> >> Ah, right. we did that. > > And thus we only need to synchronize kprobe_dispatcher()->kprobe_perf_func() > path. And afaics kprobe_perf_func() doesn't use anything which can be freed > by trace_remove_event_call? > >>>> OTOH, unregister_kprobe() waits for that. >>> >>> Yes. >>> >>> So I think we only need to move kfree(tp->call.print_fmt). > > OOPS. I was wrong. It seems that ->print_fmt is only for event/format ? > Then it is fine to kfree it right after trace_remove_event_call(). > >>> So the sequence should be: >>> >>> if (trace_remove_event_call(...)) >>> return; >>> >>> /* does synchronize_sched */ >>> unregister_kprobe(); >>> >>> kfree(everything); >>> >>> Agreed? >> >> If we can free everything after all, I'd like to do so. >> Hmm, but AFAICS, trace_remove_event_call() supposes that >> all event is disabled completely. > > Yes, but kprobe_trace_func() is really disabled?
No, currently, doesn't. We need to fix that. (Perhaps, uprobes too.)
>> A safe way is to wait rcu always right after disable_*probe >> in disable_trace_probe. If we have an unused link, we can >> free it after that. > > Aaaah... I am starting to understand... Even if kprobe_perf_func() > is fine, synchronize_sched() is calles _before_ disable_kprobe() > and thus it can't synchronize with the handlers which hit this probe > after we start synchronize_sched(). > > Did you mean this or I misssed something else?
Right, thus perf path also need to be synchronized.
Thank you,
-- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com
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