Re: [RFC][PATCH 3/4] tracing/kprobes: Fail to unregister if probeevent files are open

[Oleg Nesterov]

On 08/01, Steven Rostedt wrote:
>
> On Thu, 2013-08-01 at 16:33 +0200, Oleg Nesterov wrote:
> > On 08/01, Steven Rostedt wrote:
> > >
> > > On Thu, 2013-08-01 at 15:34 +0200, Oleg Nesterov wrote:
> > > > >
> > > > >   __unregister_trace_probe(tp);
> > > > >   list_del(&tp->list)
> > > > >   unregister_probe_event(tp) <-- fails!
> > > > >   free_trace_probe(tp)
> > > >
> > > > Yes. But again, this doesn't explain why unregister_probe_event()->
> > > > __trace_remove_event_call() can't simply proceed and
> > > > do ftrace_event_enable_disable() + remove_event_from_tracers().
> > >
> > > The problem is with the soft disable.
> >
> > Exactly! This is another (also unlikely) race we need to prevent.
> >
>
> Is there a race even with these patches?

Sorry for confusion,

> I don't see one.

Neither me, but only with these changes.

I meant that this is another reason why trace_remove_event_call() should
fail and the caller should obviously abort in this case.

> Or are you just saying that these patches fix that case too?

Yes, sorry.

Oleg.

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