linux-kernel - Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob

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Message-Id: <20160715180140.GM7094@linux.vnet.ibm.com>
Date:	Fri, 15 Jul 2016 11:01:40 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, tj@...nel.org,
	john.stultz@...aro.org, dimitrysh@...gle.com, romlem@...gle.com,
	ccross@...gle.com, tkjos@...gle.com
Subject: Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob

On Fri, Jul 15, 2016 at 06:49:39PM +0200, Oleg Nesterov wrote:
> On 07/15, Paul E. McKenney wrote:
> > On Fri, Jul 15, 2016 at 03:45:24PM +0200, Oleg Nesterov wrote:
> > > On 07/15, Paul E. McKenney wrote:
> > > >
> > > > On Fri, Jul 15, 2016 at 03:27:09PM +0200, Oleg Nesterov wrote:
> > > > >
> > > > > Heh ;) I too think it should be renamed. I'd suggest
> > > > >
> > > > > 	__rcu_sync_enter(rss);
> > > > >
> > > > > although I do not really mind and agree with any name.
> > > >
> > > > Hmmm...  Why not just move the checks out into the caller?  That
> > > > would make the intent much more clear.
> > >
> > > Hmm. which caller?
> >
> > The ones associated with a percpu_rwsem_bias of PERCPU_RWSEM_READER.
> 
> Ah. But if we add __rcu_sync_enter() instead of bias/PERCPU_RWSEM_READER.
> 
> IOW, please ignore 2/2 which adds PERCPU_RWSEM_READER, the new version
> just adds rcu_sync_sabotage() which should be renamed (and use GP_PASSED).

OK, then move the checks out into the callers that would have used
__rcu_sync_enter().  ;-)

							Thanx, Paul