linux-kernel - Re: [PATCH 2/3] rcu: Create rcu

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Message-ID: <20131004194126.GW15690@laptop.programming.kicks-ass.net>
Date:	Fri, 4 Oct 2013 21:41:26 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] rcu: Create rcu_sync infrastructure

On Fri, Oct 04, 2013 at 09:06:53PM +0200, Oleg Nesterov wrote:
> However, yes-yes-yes, I do think that we need the non-exclusive mode
> too, at least for percpu_down_write_nonexclusive() which I think we
> need as well.

I just need to disagree with the write_nonexclusive() name; the
construct I quite understand and could even agree with.

How about something like:

State excluding 'writers', but not itself:
	percpu_read_lock()
	percpu_read_unlock()

State excluding readers, but not itself:
	percpu_non_read_lock();
	percpu_non_read_unlock();

Full exclusive state:
	percpu_write_lock();
	percpu_write_unlock();

At which point I start to have doubts about the percpu prefix.. ;-)
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