linux-kernel - Re: [PATCH for-3.3] mempool: clean up and document synchronization and memory barrier usage

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Message-ID: <20111221164459.GA9213@google.com>
Date:	Wed, 21 Dec 2011 08:44:59 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	David Howells <dhowells@...hat.com>
Subject: Re: [PATCH for-3.3] mempool: clean up and document synchronization
 and memory barrier usage

Ooh, missed something.

On Wed, Dec 21, 2011 at 08:37:15AM -0800, Tejun Heo wrote:
> Yes, that's another way to put it.  It's much easier to understand if
> you draw a graph with time on x axis and curr_nr on y and mark which
> curr_nr values are guaranteed to be visible to whom.  If at any point
> of time, a freeing task sees curr_nr == min_nr, it's guaranteed that
> either it's staying that way or, if not, someone else will see the
> newly decremented value.

And there will be enough "someone elses" to restore curr_nr == min_nr.

Thanks.

-- 
tejun
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