(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: [email protected] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
