From: Namhyung Kim <namhyung@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-team@lge.com
Subject: Re: [PATCH 1/4] ftrace: Fix function pid filter on instances
Date: Wed, 29 Mar 2017 11:42:27 +0900 [thread overview]
Message-ID: <20170329024227.GC19448@sejong> (raw)
In-Reply-To: <20170328222855.78af0d53@grimm.local.home>
On Tue, Mar 28, 2017 at 10:28:55PM -0400, Steven Rostedt wrote:
> On Wed, 29 Mar 2017 11:20:37 +0900
> Namhyung Kim <namhyung@kernel.org> wrote:
>
>
> > > Actually, if this is called after event_trace_del_tracer(), the tr is
> > > already invisible and nothing new should change.
> >
> > I don't follow. After event_trace_del_tracer(), the tr is invisible
> > from the probe of event tracing but still is visible from the probe of
> > function tracing, right?
>
> Well, nothing should be able to get to the set_ftrace_filter file when
> there. Because of the tr->ref count. But keeping the lock is safer
> regardless, and it's not a fast path, so the extra overhead if the lock
> isn't needed is no big deal.
Oh, I meant if a pid filter was already set when removing the
instance. Function filters should be inactive since function tracer
was finished (via tracing_set_nop), but the probe on sched_switch
event (for pid filter) is still active and references the tr.
Thanks,
Namhyung
>
> >
> > >
> > > Make a wrapper around clear_ftrace_pids() and call that instead. We
> > > don't even need to take a lock, but as I see there's a lockdep test for
> > > ftrace_lock, we should still do so just to be safe.
> >
> > Right, that's why I call ftrace_pid_reset() instead of
> > clear_ftrace_pids(). So do you prefer adding a new wrapper like below
> > rather than reusing ftrace_pid_reset() with a new argument?
>
> Yes, because the bool passed in is confusing. A separate function like
> below is more descriptive.
>
> -- Steve
>
> >
> > Thanks,
> > Namhyung
> >
> >
> > >
> > > void ftrace_clear_pids(struct trace_array *tr)
> > > {
> > > mutex_lock(&ftrace_lock);
> > >
> > > clear_ftrace_pids(tr);
> > >
> > > mutex_unlock(&ftrace_lock);
> > > }
next prev parent reply other threads:[~2017-03-29 2:42 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-29 1:46 [PATCH 0/4] ftrace: Add 'function-fork' trace option (v1) Namhyung Kim
2017-03-29 1:46 ` [PATCH 1/4] ftrace: Fix function pid filter on instances Namhyung Kim
2017-03-29 2:08 ` Steven Rostedt
2017-03-29 2:20 ` Namhyung Kim
2017-03-29 2:28 ` Steven Rostedt
2017-03-29 2:42 ` Namhyung Kim [this message]
2017-03-29 2:58 ` Steven Rostedt
2017-03-29 3:02 ` Namhyung Kim
2017-03-29 2:25 ` Namhyung Kim
2017-03-29 1:46 ` [PATCH 2/4] ftrace: Add 'function-fork' trace option Namhyung Kim
2017-03-29 2:18 ` Steven Rostedt
2017-03-29 2:21 ` Steven Rostedt
2017-03-29 1:46 ` [PATCH 3/4] selftests: ftrace: Add -l/--logdir option Namhyung Kim
2017-03-29 8:30 ` Masami Hiramatsu
2017-03-29 1:46 ` [PATCH 4/4] selftests: ftrace: Add a testcase for function PID filter Namhyung Kim
2017-03-29 1:51 ` [PATCH 0/4] ftrace: Add 'function-fork' trace option (v1) Steven Rostedt
2017-03-30 0:54 ` Masami Hiramatsu
2017-03-30 1:40 ` Namhyung Kim
2017-03-30 13:49 ` Steven Rostedt
2017-03-30 22:25 ` Masami Hiramatsu
2017-03-30 22:28 ` Steven Rostedt
2017-04-17 2:44 [PATCH 0/4] ftrace: Add 'function-fork' trace option (v2) Namhyung Kim
2017-04-17 2:44 ` [PATCH 1/4] ftrace: Fix function pid filter on instances Namhyung Kim
2017-04-17 11:52 ` Masami Hiramatsu
2017-04-17 13:00 ` Namhyung Kim
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