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Date: Mon, 27 Mar 2006 01:30:00 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Andrew Morton <akpm@osdl.org>
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
Message-ID: <20060326233000.GA21711@elte.hu>
References: <20060325184612.GF16724@elte.hu> <20060325220728.3d5c8d36.akpm@osdl.org> <20060326160353.GA13282@elte.hu> <20060326111645.3cf2c206.akpm@osdl.org>
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* Andrew Morton <akpm@osdl.org> wrote:

> 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))

ah, indeed, you are right.

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

ok, i left it as-is for now.

	Ingo