Re: [RFC][PATCH 5/8] rtmutex: Clean up

[Peter Zijlstra]

On Tue, Jun 14, 2016 at 01:08:13PM +0100, Juri Lelli wrote:
> > +	postunlock = rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
> >  
> >  	/*
> >  	 * First unlock HB so the waiter does not spin on it once he got woken
> > +	 * up. Then wakeup the waiter by calling rt_mutex_postunlock(). Priority
> > +	 * is already adjusted and preemption is disabled to avoid inversion.
> >  	 */
> >  	spin_unlock(&hb->lock);
> >  
> > +	if (postunlock)
> > +		rt_mutex_postunlock(&wake_q);
> 
> I'm most probably missing something, but don't we still need to call
> wake_up_q() even when postunlock is false? IIUC, we were always doing
> that, rt_mutex_postunlock(), before this change (only calling
> preempt_enable() was conditional).

Note that rt_mutex_slowunlock() only uses wake_q on the true path. When
it returns false, it will not have placed a task to wake up.