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SubjectRe: [PATCH -v2 1/9] rtmutex: Deboost before waking up the top waiter
On Wed, Sep 28, 2016 at 11:07:40AM +0200, Sebastian Andrzej Siewior wrote:
> On 2016-09-26 14:32:14 [+0200], Peter Zijlstra wrote:
> > --- a/kernel/futex.c
> > +++ b/kernel/futex.c
> > @@ -1374,9 +1374,8 @@ static int wake_futex_pi(u32 __user *uad
> > * scheduled away before the wake up can take place.
> > */
> > spin_unlock(&hb->lock);
> > - wake_up_q(&wake_q);
> > - if (deboost)
> > - rt_mutex_adjust_prio(current);
> > +
> > + rt_mutex_postunlock(&wake_q, deboost);
>
> This breaks -RT. Before that spin_unlock() you do a preempt_disable()
> which means you had one spinlock with enabled preemption and now you get
> one unlock with disabled preemption. And this breaks migrate_disable() /
> enable (because we take the fast path in the in_atomic() case).

Oh crud, the hb lock is not raw :/

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