linux-kernel - Re: [PATCH] Generic percpu refcounting

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Date:	Mon, 3 Jun 2013 15:39:31 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Kent Overstreet <koverstreet@...gle.com>
Cc:	linux-kernel@...r.kernel.org, Zach Brown <zab@...hat.com>,
	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mark Fasheh <mfasheh@...e.com>,
	Joel Becker <jlbec@...lplan.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jens Axboe <axboe@...nel.dk>,
	Asai Thambi S P <asamymuthupa@...ron.com>,
	Selvan Mani <smani@...ron.com>,
	Sam Bradshaw <sbradshaw@...ron.com>,
	Jeff Moyer <jmoyer@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] Generic percpu refcounting

On Fri, May 31, 2013 at 03:26:45PM -0700, Kent Overstreet wrote:
> This implements a refcount with similar semantics to
> atomic_get()/atomic_dec_and_test() - but percpu.
> 
> It also implements two stage shutdown, as we need it to tear down the
> percpu counts.  Before dropping the initial refcount, you must call
> percpu_ref_kill(); this puts the refcount in "shutting down mode" and
> switches back to a single atomic refcount with the appropriate barriers
> (synchronize_rcu()).
> 
> It's also legal to call percpu_ref_kill() multiple times - it only returns
> true once, so callers don't have to reimplement shutdown synchronization.
> 
> [akpm@...ux-foundation.org: fix build]
> [akpm@...ux-foundation.org: coding-style tweak]
> Signed-off-by: Kent Overstreet <koverstreet@...gle.com>
> Cc: Zach Brown <zab@...hat.com>
> Cc: Felipe Balbi <balbi@...com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Mark Fasheh <mfasheh@...e.com>
> Cc: Joel Becker <jlbec@...lplan.org>
> Cc: Rusty Russell <rusty@...tcorp.com.au>
> Cc: Jens Axboe <axboe@...nel.dk>
> Cc: Asai Thambi S P <asamymuthupa@...ron.com>
> Cc: Selvan Mani <smani@...ron.com>
> Cc: Sam Bradshaw <sbradshaw@...ron.com>
> Cc: Jeff Moyer <jmoyer@...hat.com>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: Benjamin LaHaise <bcrl@...ck.org>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: Christoph Lameter <cl@...ux-foundation.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Reviewed-by: "Theodore Ts'o" <tytso@....edu>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>

Applied to percpu/for-3.11.  Andrew, I removed your SOB as the patch
is routed outside -mm.  Please let me know if you want
reviewed/ackd-by added.

 git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu.git for-3.11

Thanks a lot!

-- 
tejun
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