Re: [PATCH][GIT PULL][v2.6.35] perf/tracing: Fix regression of perflosing kprobe events

From: Masami Hiramatsu
Date: Fri Jun 11 2010 - 04:05:37 EST


Steven Rostedt wrote:
> Ingo,
>
> Please pull the latest tip/perf/urgent tree, which can be found at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
> tip/perf/urgent
>
>
> Steven Rostedt (1):
> perf/tracing: Fix regression of perf losing kprobe events
>
> ----
> kernel/trace/trace_event_perf.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
> ---------------------------
> commit a8fb2608053547bc3152ea61a5ec7cdfce5d942c
> Author: Steven Rostedt <srostedt@xxxxxxxxxx>
> Date: Thu Jun 10 14:53:16 2010 -0400
>
> perf/tracing: Fix regression of perf losing kprobe events
>
> With the addition of the code to shrink the kernel tracepoint
> infrastructure, we lost kprobes being traced by perf. The reason
> is that I tested if the "tp_event->class->perf_probe" existed before
> enabling it. This prevents "ftrace only" events (like the function
> trace events) from being enabled by perf.
>
> Unfortunately, kprobe events do not use perf_probe. This causes
> kprobes to be missed by perf. To fix this, we add the test to
> see if "tp_event->class->reg" exists as well as perf_probe.
>
> Normal trace events have only "perf_probe" but no "reg" function,
> and kprobes and syscalls have the "reg" but no "perf_probe".
> The ftrace unique events do not have either, so this is a valid
> test. If a kprobe or syscall is not to be probed by perf, the
> "reg" function is called anyway, and will return a failure and
> prevent perf from probing it.
>
> Reported-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
> Tested-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
> Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>

Thank you for fixing,

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>


>
> diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
> index e6f6588..8a2b73f 100644
> --- a/kernel/trace/trace_event_perf.c
> +++ b/kernel/trace/trace_event_perf.c
> @@ -96,7 +96,9 @@ int perf_trace_init(struct perf_event *p_event)
> mutex_lock(&event_mutex);
> list_for_each_entry(tp_event, &ftrace_events, list) {
> if (tp_event->event.type == event_id &&
> - tp_event->class && tp_event->class->perf_probe &&
> + tp_event->class &&
> + (tp_event->class->perf_probe ||
> + tp_event->class->reg) &&
> try_module_get(tp_event->mod)) {
> ret = perf_trace_event_init(tp_event, p_event);
> break;
>
>
>
>


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