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Date: Sun, 26 Mar 2006 11:16:45 -0800
From: Andrew Morton <akpm@osdl.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, torvalds@osdl.org,
       arjan@infradead.org, simlo@phys.au.dk
Subject: Re: [patch] PI-futex: -V2
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In-Reply-To: <20060326160353.GA13282@elte.hu>
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	<20060326160353.GA13282@elte.hu>
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Ingo Molnar <mingo@elte.hu> wrote:
>
> > > +	for (;;) {
>  > > +		if (top_waiter)
>  > > +			plist_del(&top_waiter->pi_list_entry,
>  > > +				  &owner->pi_waiters);
>  > > +
>  > > +		if (waiter && waiter == rt_mutex_top_waiter(lock)) {
>  > 
>  > rt_mutex_top_waiter() can never return NULL, so the test for NULL 
>  > could be removed.
> 
>  it might be NULL if adjust_pi_chain() is called from remove_waiter(), 
>  and next_waiter there is NULL (because !rt_mutex_has_waiters() after the 
>  removal of the current waiter).

Yes, `waiter' might be NULL.  But rt_mutex_top_waiter() will never return
NULL.  So it might be possible to just do

	if (waiter == rt_mutex_top_waiter(lock))

Which might actually be less efficient, and more obscure.  Just pointing it
out.