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From: Steven Rostedt <rostedt@goodmis.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Tom Zanussi <tom.zanussi@linux.intel.com>,
	Clark Williams <williams@redhat.com>,
	Karim Yaghmour <karim.yaghmour@opersys.com>,
	Brendan Gregg <bgregg@netflix.com>,
	Joel Fernandes <joelaf@google.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	linux-rt-users@vger.kernel.org, kernel-team@lge.com
Subject: Re: [RFC][PATCH 06/10] tracing: Add trigger file for trace_markers tracefs/ftrace/print
Date: Mon, 14 May 2018 11:04:36 -0400	[thread overview]
Message-ID: <20180514110436.336b214b@gandalf.local.home> (raw)
In-Reply-To: <20180514031322.GB9220@sejong>

On Mon, 14 May 2018 12:13:22 +0900
Namhyung Kim <namhyung@kernel.org> wrote:

> On Fri, May 11, 2018 at 03:49:33PM -0400, Steven Rostedt wrote:
> > From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
> > 
> > Allow writing to the trace_markers file initiate triggers defined in
> > tracefs/ftrace/print/trigger file. This will allow of user space to trigger
> > the same type of triggers (including histograms) that the trace events use.
> > 
> > Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
> > Cc: Clark Williams <williams@redhat.com>
> > Cc: Karim Yaghmour <karim.yaghmour@opersys.com>
> > Cc: Brendan Gregg <bgregg@netflix.com>
> > Suggested-by: Joel Fernandes <joelaf@google.com>
> > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> > ---  
> 
> [SNIP]
> > diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
> > index e3a658bac10f..de3fce14cd00 100644
> > --- a/kernel/trace/trace_entries.h
> > +++ b/kernel/trace/trace_entries.h
> > @@ -230,7 +230,7 @@ FTRACE_ENTRY(bprint, bprint_entry,
> >  	FILTER_OTHER
> >  );
> >  
> > -FTRACE_ENTRY(print, print_entry,
> > +FTRACE_ENTRY_REG(print, print_entry,
> >  
> >  	TRACE_PRINT,
> >  
> > @@ -242,7 +242,9 @@ FTRACE_ENTRY(print, print_entry,
> >  	F_printk("%ps: %s",
> >  		 (void *)__entry->ip, __entry->buf),
> >  
> > -	FILTER_OTHER
> > +	FILTER_OTHER,
> > +
> > +	 ftrace_event_register  
> 
> I wonder this is still needed since you added __find_event_file()
> which ignores the reg field.  Maybe I'm missing something..

No, that's not the reason for it. The reason is due to the
event_trigger_callback() function. I'll update the changelog to specify
this.

We have something like:

 # echo snapshot > events/ftrace/print/trigger

Which will do:

  event_trigger_write() {
    event_trigger_regex_write() {
      trigger_process_regex() {
        for p in trigger_commands {
          p->func(); /* trigger_snapshot_cmd->func */
            event_trigger_callback() {
              cmd_ops->reg() /* register_trigger() */ {
                trace_event_trigger_enable_disable() {
                  trace_event_enable_disable() {
                    call->class->reg();

Without this patch, we jump to NULL and BOOM!
                

> 
> Anyway it looks whitespace damaged.
>

Thanks, I'll fix it up.

-- Steve

  reply	other threads:[~2018-05-14 15:04 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-11 19:49 [RFC][PATCH 00/10] tracing: Add triggers to trace_marker writes Steven Rostedt
2018-05-11 19:49 ` [RFC][PATCH 01/10] tracing: Do not reference event data in post call triggers Steven Rostedt
2018-05-12 12:04   ` Masami Hiramatsu
2018-05-11 19:49 ` [RFC][PATCH 02/10] tracing: Add __find_event_file() to find event files without restrictions Steven Rostedt
2018-05-11 19:49 ` [RFC][PATCH 03/10] tracing: Have event_trace_init() called by trace_init_tracefs() Steven Rostedt
2018-05-11 19:49 ` [RFC][PATCH 04/10] tracing: Add brackets in ftrace event dynamic arrays Steven Rostedt
2018-05-11 19:49 ` [RFC][PATCH 05/10] tracing: Do not show filter file for ftrace internal events Steven Rostedt
2018-05-11 19:49 ` [RFC][PATCH 06/10] tracing: Add trigger file for trace_markers tracefs/ftrace/print Steven Rostedt
2018-05-14  3:13   ` Namhyung Kim
2018-05-14 15:04     ` Steven Rostedt [this message]
2018-05-16  7:49       ` Namhyung Kim
2018-05-16 10:37         ` Steven Rostedt
2018-05-11 19:49 ` [RFC][PATCH 07/10] tracing: Have zero size length in filter logic be full string Steven Rostedt
2018-05-12 12:40   ` Masami Hiramatsu
2018-05-12 17:27     ` Steven Rostedt
2018-05-12 18:32   ` Yann Ylavic
2018-05-14  2:23     ` Namhyung Kim
2018-05-14 14:12     ` Steven Rostedt
2018-05-11 19:49 ` [RFC][PATCH 08/10] tracing: Prevent further users of zero size static arrays in trace events Steven Rostedt
2018-05-11 19:49 ` [RFC][PATCH 09/10] tracing: Allow histogram triggers to access ftrace internal events Steven Rostedt
2018-05-11 19:49 ` [RFC][PATCH 10/10] tracing: Document trace_marker triggers Steven Rostedt

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