On Thu, Jan 29, 2015 at 4:04 PM, Alexei Starovoitov <ast@xxxxxxxxxxxx> wrote: > On Wed, Jan 28, 2015 at 10:41 PM, Namhyung Kim <namhyung@xxxxxxxxxx> wrote: >> >> I think it's not a problem of bpf. An user process can be killed >> anytime while it enabed events without bpf. The only thing it should >> care is the auto-unload IMHO. > > ok. I think it does indeed make sense to decouple the logic. > We can add 'auto_enable' file to achieve desired Ctrl-C behavior. > While the 'auto_enable' file is open the event will be enabled > and writes to 'enable' file will be ignored. > As soon as file closes, the event is auto-disabled. > Then user space will use 'bpf' file to attach/auto-unload > and 'auto_enable' file together. > Seem there would be a use for such 'auto_enable' > without bpf as well. Why do you want such an 'auto_enable' feature? I guess it's enough just to keep an event in the soft-disabled state and run a bpf program before the check. > >> I'm okay for not calling bpf program in NMI but not for disabling events. >> >> Suppose an user was collecting an event (including in NMI) and then >> [s]he also wanted to run a bpf program. So [s]he wrote a program >> always return 1. But after attaching the program, it didn't record >> the event in NMI.. Isn't that a problem? > > ok, I think 'if (in_nmi()) return 1;' will work then, right? > Or you're thinking something else ? Nope, returning 1 would be okay.. > >> Right. I think bpf programs belong to a user process but events are >> global resource. Maybe you also need to consider attaching bpf >> program via perf (ioctl?) interface.. > > yes. I did. Please see my reply to Masami. > ioctl only works for tracepoints. What was the problem of kprobes then? :) Thanks, Namhyung -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
