Re: Audio I/O parameters

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On Fri, 2 Aug 2013, Steven Rostedt wrote:

> On Fri, 2013-08-02 at 16:36 +0200, Peter Zijlstra wrote:
> > On Fri, Aug 02, 2013 at 10:14:39AM -0400, Alan Stern wrote:
> > > URL Clas-3286    2d.h.    1us : local_clock <-perf_event_update_userpage
> > > URL Clas-3286    2d.h.    2us : watchdog_overflow_callback <-__perf_event_overflow
> > > URL Clas-3286    2d.h.    3us : arch_trigger_all_cpu_backtrace_handler <-nmi_handle.isra.0
> > > URL Clas-3286    2d.h.    3us : perf_ibs_nmi_handler <-nmi_handle.isra.0
> > > URL Clas-3286    2d.h.    3us : perf_ibs_handle_irq <-perf_ibs_nmi_handler
> > > URL Clas-3286    2d.h.    4us : perf_ibs_handle_irq <-perf_ibs_nmi_handler
> > > URL Clas-3286    2d.h.    4us!: rcu_nmi_exit <-do_nmi
> > 
> > What's cute is that the trace starts when the NMI handler does
> > local_irq_save(), _not_ when the NMI starts, which is where the hardware
> > actually disabled interrupts.
> 
> Yeah, the NMI can be messing with the tracer. It's built on top of
> lockdep, which does not handle NMIs. Perhaps we can add NMI handling to
> the latency tracer, but that may need a bit of work to do that.

Do you have any suggestions with regard to the two questions in my 
previous email?

Alan Stern

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