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Subject: Re: [PATCH] break_lock forever broken
From: Arjan van de Ven <arjan@infradead.org>
To: Hugh Dickins <hugh@veritas.com>
Cc: Andrew Morton <akpm@osdl.org>, mingo@elte.hu, nickpiggin@yahoo.com.au,
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Date: Sun, 13 Mar 2005 14:52:11 +0100
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On Sun, 2005-03-13 at 09:35 +0000, Hugh Dickins wrote:
> On Sun, 13 Mar 2005, Arjan van de Ven wrote:
> > > 							\
> > > +	if ((lock)->break_lock)						\
> > > +		(lock)->break_lock = 0;					\
> > >  }									\
> > if it really worth an conditional there? the cacheline of the lock is
> > made dirty anyway on unlock, so writing an extra 0 is like almost free
> > (maybe half a cycle) while a conditional jump can be 100+....
> 
> I wondered the same, I don't know and would defer to those who do:
> really I was just following the style of where break_lock is set above,
> which follows soon (unless preempted) after a _raw_whatever_trylock.

if the cacheline is dirtied previously it's just free to do the write so
I suggest to remove the conditional...