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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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