On Tue, 18 Jun 2019 12:23:22 -0400 Steven Rostedt <[email protected]> wrote:
> On Wed, 19 Jun 2019 01:14:09 +0900 > Masami Hiramatsu <[email protected]> wrote: > > > On Mon, 17 Jun 2019 21:56:43 -0400 > > Steven Rostedt <[email protected]> wrote: > > > > > > > +static nokprobe_inline struct trace_kprobe * > > > > +trace_kprobe_primary_from_call(struct trace_event_call *call) > > > > +{ > > > > + struct trace_probe *tp = trace_probe_primary_from_call(call); > > > > + > > > > + return container_of(tp, struct trace_kprobe, tp); > > > > > > > > > Hmm, is there a possibility that trace_probe_primary_from_call() may > > > not have a primary? > > > > Good question! Of course if given event_call is not a kprobe event, > > it doesn't have primary (or any) trace_probe. But that must not happen > > unless user misuses it. > > And that list never be the empty, when the last trace probe is released, > > the event_call also unregistered and released. See unregister_trace_kprobe() > > for details. If there is no siblings on the list, the event_call is also > > unregistered before unregistering kprobes, and after unregistering kprobes > > the list is unlinked. > > (Note that unregister_kprobe() will wait a quiescence period > > before return. This means all probe handlers are done before that.) > > Yeah, I thought something like that. But perhaps the > trace_probe_primary_from_call() code should add a WARN_ON() is the list > is empty. OK, I'll add that, and check in all callers. > > > > > > > > - ret = __enable_trace_kprobe(tk); > > > > - if (ret) { > > > > + enabled = false; > > > > + list_for_each_entry(pos, trace_probe_probe_list(tp), list) { > > > > + tk = container_of(pos, struct trace_kprobe, tp); > > > > + ecode = __enable_trace_kprobe(tk); > > > > + if (ecode) > > > > + ret = ecode; /* Save the last error code */ > > > > + else > > > > + enabled = true; > > > > > > So, if we have some enabled but return an error code, what should a > > > caller think of that? Wouldn't it be an inconsistent state? > > > > Oops, good catch! > > This part is related to caller (ftrace/perf) so should be more careful. > > Usually, kprobe enablement should not fail. If one of them has > > gone (like a probe on unloaded module), it can be fail but that > > should be ignored. I would like to add some additional check so that > > - If all kprobes are on the module which is unloaded, enablement > > must be failed and return error. > > - If any kprobe is enabled, and others are on non-exist modules, > > it should succeeded and return OK. > > - If any kprobe caused an error not because of unloaded module, > > all other enablement should be canceled and return error. > > > > Is that OK for you? > > > > Sounds good to me. Thank you! -- Masami Hiramatsu <[email protected]>
