linux-kernel - Re: Memory allocator semantics

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Message-ID: <alpine.DEB.2.10.1402111242380.28186@nuc>
Date:	Tue, 11 Feb 2014 12:43:35 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Pekka Enberg <penberg@...nel.org>
cc:	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Matt Mackall <mpm@...enic.com>
Subject: Re: Memory allocator semantics

On Tue, 11 Feb 2014, Pekka Enberg wrote:

> So again, there's nothing in (A) that the memory allocator is
> concerned about.  kmalloc() makes no guarantees whatsoever about the
> visibility of "r1" across CPUs.  If you're saying that there's an
> implicit barrier between kmalloc() and kfree(), that's an unintended
> side-effect, not a design decision AFAICT.

I am not sure that this side effect necessarily happens. The SLUB fastpath
does not disable interrupts and only uses a cmpxchg without lock
semantics.

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