linux-kernel - Re: [PATCH 3/4] locking: Introduce smp_cond

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Message-ID: <20151203203159.GW17308@twins.programming.kicks-ass.net>
Date:	Thu, 3 Dec 2015 21:31:59 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Davidlohr Bueso <dave@...olabs.net>
Cc:	mingo@...nel.org, oleg@...hat.com, linux-kernel@...r.kernel.org,
	paulmck@...ux.vnet.ibm.com, boqun.feng@...il.com, corbet@....net,
	mhocko@...nel.org, dhowells@...hat.com,
	torvalds@...ux-foundation.org, will.deacon@....com,
	waiman.long@....com, pjt@...gle.com
Subject: Re: [PATCH 3/4] locking: Introduce smp_cond_acquire()

On Thu, Dec 03, 2015 at 11:41:39AM -0800, Davidlohr Bueso wrote:

> >+#define smp_cond_acquire(cond)	do {		\
> >+	while (!(cond))				\
> >+		cpu_relax();			\
> >+	smp_rmb(); /* ctrl + rmb := acquire */	\
> >+} while (0)
> 
> So this hides the fact that we actually are waiting on the cond, as opposed
> to conditional acquiring. Could it be renamed to something like smp_waitcond_acquire()?

Right, I'm conflicted about that. On the one hand you're right, on the
other hand we spin-wait so the next person will want it called
smp_spin_wait_cond_acquire(), also it gets terribly long either way :/

bike-shed away I imagine.
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