On Wed, Jan 28, 2015 at 9:39 PM, Masami Hiramatsu <masami.hiramatsu...@hitachi.com> wrote: > > Maybe, would we need a reference counter for each event? :)
when we would want multiple users to attach different programs to the same event, then yes. Right now I'd rather have things simple. > Actually, ftrace event is not similar to perf-event which ktap > is based on, ftrace event interface is always exported via > debugfs, this means users can share the event for different > usage. yes.I've been thinking to extend perf_event ioctl to attach programs, but right now it's only supporting tracepoints and kprobe seems not trivial to add. So I went for tracefs style of attaching for now. > One possible other solution is to add a instance-lock interface > for each ftrace instance and lock it by bpf. Then, other users > can not enable/disable the events in the instance. the user space can synchronize itself via flock. kernel doesn't need to arbitrate. If one user process attached a program that auto-enabled an event and another process did 'echo 0 > enable', it's fine. I think it's a feature instead of a bug. Both users are root anyway. The more we talk about it, the more I like a new 'bpf' file approach within tracefs (that I've mentioned in cover letter) with auto-enable/disable logic to make it clear that it's different from traditional global 'filter' file. -- 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/
