Re: [tip:sched/core] cpu: Remove incorrect BUG_ON

Peter Zijlstra
2010-11-23T15:05:06Z

On Tue, 2010-11-23 at 15:39 +0100, Oleg Nesterov wrote:
> On 11/23, tip-bot for Peter Zijlstra wrote:
> >
> > --- a/kernel/cpu.c
> > +++ b/kernel/cpu.c
> > @@ -249,8 +249,11 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
> > * The migration_call() CPU_DYING callback will have removed all
> > * runnable tasks from the cpu, there's only the idle task left now
> > * that the migration thread is done doing the stop_machine thing.
> > + *
> > + * Wait for the stop thread to go away.
> > */
> > - BUG_ON(!idle_cpu(cpu));
> > + while (!idle_cpu(cpu))
> > + cpu_relax();
>
> Yes... but I still can't understand why should we wait at all.
>
> Peter, I am just curious, help ;)

Ah,. uhm,. you mean, not do anything at all?

Dunno, really, let me try and read the code there.