Re: [patch 1/2] idle profile hits with NOHZ

Thomas Gleixner
2009-05-28T20:20:04Z

On Thu, 28 May 2009, Martin Schwidefsky wrote:
> --- quilt-2.6.orig/kernel/time/tick-sched.c
> +++ quilt-2.6/kernel/time/tick-sched.c
> @@ -166,6 +166,7 @@ static void tick_nohz_stop_idle(int cpu)
> ts->idle_lastupdate = now;
> ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
> ts->idle_active = 0;
> + ts->idle_pc = profile_pc(get_irq_regs());

Hmm, tick_nohz_stop_idle() is called from
tick_nohz_restart_sched_tick() as well in the context of the idle
task.

I think there is no guarantee that get_irq_regs() will return
anything useful in thread context.

So get_irq_regs() might return a NULL pointer which will explode
some of the profile_pc() implementations. If not it can still feed
total nonsense to the profile_hits() call.

Thanks,

tglx