Re: [PATCH 1/2] hrtimer: Consider preemption when migrating hrtimercpu_bases

[Michael Bohan]

On 4/18/2013 2:40 AM, Thomas Gleixner wrote:
> On Wed, 10 Apr 2013, Michael Bohan wrote:
>
> > When switching to a new cpu_base in switch_hrtimer_base(), we
> > briefly enable preemption by unlocking the cpu_base lock in two
> > places. During this interval it's possible for the running thread
> > to be swapped to a different CPU.
> >
> > Consider the following example:
> >
> > CPU #0                                 CPU #1
> > ----                                   ----
> > hrtimer_start()                        ...
> >   lock_hrtimer_base()
> >   switch_hrtimer_base()
> >    this_cpu = 0;
> >    target_cpu_base = 0;
> >    raw_spin_unlock(&cpu_base->lock)
> > <migrate to CPU 1>
>
> Errm. switch_hrtimer_base() is called with interrupts disabled and
> they stay disabled, so how exactly is the task going to be migrated?

My mistake - I missed that important fact. Please disregard this.

Thanks,
Mike

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