lkml.org 
[lkml]   [2017]   [Mar]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/4] ftrace: Fix function pid filter on instances
On Wed, 29 Mar 2017 11:42:27 +0900
Namhyung Kim <namhyung@kernel.org> wrote:

> 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.
>

I think we are talking about two different things. I was simply talking
about the need to take the ftrace_lock or not in the
clear_ftrace_pids() call here. I don't think we have to, because nothing
should be in contention with it at that point. But it doesn't hurt to
take it.

-- Steve

\
 
 \ /
  Last update: 2017-03-29 05:01    [W:0.094 / U:0.316 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site