Re: [PATCH] tracing/ftrace: add missing wake-up on some callsites

Ingo Molnar
2009-02-23T18:10:00Z

* Steven Rostedt <rostedt@goodmis.org> wrote:

> On Mon, 23 Feb 2009, Ingo Molnar wrote:
>
> > * Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> > > > Which would send a delayed work to wake up?
> > >
> > > No, I was thinking that trace_delay_wake_up() would be
> > > called by these dangerous call sites. Then a per_cpu flag
> > > could be set. We could have a trace point in the scheduler
> > > code that is outside holding a runqueue lock, and this
> > > trace point would call a trace function that will clear
> > > the per cpu flag, and then call trace_wake_up().
> >
> > No, that's very roundabout and ugly. If we putting a
> > tracepoint there we might as well put real scheduler code
> > there that looks for such a flag. But i'm not convinced we
> > need a flag ...
>
> Just a suggestion. I was trying to keep the tracer from being
> an overhead. But what else would you suggest? Just having the
> scheduler call trace_wakeup?

i think we could use a TIF flag to trigger a wakeup at the
return-to-userspace (or return-from-IRQ) stage or so?

Ingo