linux-kernel - Re: [RFC][PATCH 5/7] jump_label: Rework update logic

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Date:	Tue, 28 Jul 2015 07:54:34 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org,
	jasonbaron0@...il.com, bp@...en8.de, luto@...capital.net,
	tglx@...utronix.de, rostedt@...dmis.org, will.deacon@....com,
	liuj97@...il.com, rabin@....in, ralf@...ux-mips.org,
	ddaney@...iumnetworks.com, benh@...nel.crashing.org,
	michael@...erman.id.au, davem@...emloft.net
Subject: Re: [RFC][PATCH 5/7] jump_label: Rework update logic

On Mon, Jul 27, 2015 at 06:30:05PM +0200, Peter Zijlstra wrote:
> On Mon, Jul 27, 2015 at 12:47:14PM +0200, Peter Zijlstra wrote:
> > @@ -68,13 +63,8 @@ void static_key_slow_inc(struct static_k
> >  		return;
> >  
> >  	jump_label_lock();
> > +	if (atomic_inc_and_test(&key->enabled))
> 
> atomic_inc_return() == 1, works _much_ better.

Confirmed. With this change, the jump_label_init() patch, plus the
changes in s390 inline asm everything works for me.

There are a couple of places in s390 code where the DEFINE_STATIC_KEY_FALSE
and static_branch_likely() combination would make sense.

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