On Fri, 2013-06-28 at 16:27 +0200, Oleg Nesterov wrote:
> On 06/28, Masami Hiramatsu wrote:
> >
> > @@ -232,19 +246,21 @@ enable_trace_probe(struct trace_probe *tp, struct
> > ftrace_event_file *file)
> > rcu_assign_pointer(tp->files, new);
> > tp->flags |= TP_FLAG_TRACE;
> >
> > + ret = __enable_trace_probe(tp);
> > + if (ret < 0) {
> > + /* Write back the old list */
> > + rcu_assign_pointer(tp->files, old);
> > + old = new; /* "new" must be freed */
> > + }
> > +
> > if (old) {
> > /* Make sure the probe is done with old files */
> > synchronize_sched();
> > kfree(old);
> > }
>
> Ah, but this conflicts with the other changes I sent. They have
> your acks, and iiuc Steven is going to apply them.
I'll see if I can solve any conflicts. I need to get my -rt versions out
and start on the new 3.6 stable today. Then after that, I plan on going
though and getting all the tracing patches settled.
Thanks,
-- Steve
>
> Besides, this fix is not complete afaics, we should also clear
> TP_FLAG_TRACE/PROFILE if __enable_trace_probe() fails.
>
> Perhaps you can do this later, on top of the pending changes?
>
> Or. Given that this patch assumes that enable_kprobe() must succed,
> can't we make a minimal change for now?
>
> -------------------------------------------------------------------------------
> [PATCH] tracing/kprobe: WARN() if enable_kprobe() fails.
>
> enable_trace_probe() doesn't recover tp->files/flags if enable_kprobe()
> fails, this looks confusing.
>
> However, enable_kprobe() must not fail at this time except for unknown
> bug or changing the implementation of enable_kprobe(), because usual
> failure cases (not registered or gone) are already filtered.
>
> So this patch simply adds WARN_ON(ret) to document this fact, even if
> it makes sense to cleanup the logic anyway later.
>
> Reported-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
> ---
> kernel/trace/trace_kprobe.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 5c070db..bb608b5 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -220,6 +220,7 @@ enable_trace_probe(struct trace_probe *tp, struct
> ftrace_event_file *file)
> ret = enable_kretprobe(&tp->rp);
> else
> ret = enable_kprobe(&tp->rp.kp);
> + WARN_ON(ret);
> }
> out:
> return ret;
--
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