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SubjectRe: perf regression: failed to stat syscalls events
On Thu, Jun 24, 2010 at 01:58:45PM +0800, Peter Zijlstra wrote:
> On Thu, 2010-06-24 at 09:44 +0800, Wu Fengguang wrote:
> > On Thu, Jun 24, 2010 at 09:39:15AM +0800, Wu Fengguang wrote:
> > > Greetings,
> > >
> > > I noticed that
> > >
> > > # perf stat -e syscalls:sys_enter_mmap true
> > >
> > > refuse to work on 2.6.35-rc1. The last working kernel is 2.6.34.
> >
> > Other events like lock:* or block:* or whatever continue to work.
> > So this is a problem specific to syscalls:*.
>
> Does your tree contain:

Thanks, it worked! This patch is missing from linux-2.6.git for now.

Thanks,
Fengguang


> ---
> commit a8fb2608053547bc3152ea61a5ec7cdfce5d942c
> Author: Steven Rostedt <srostedt@redhat.com>
> 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@linux.vnet.ibm.com>
> Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
>
> 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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