Date: Fri, 29 Jun 2007 13:16:57 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: David Miller <davem@davemloft.net>, clameter@sgi.com, hugh@veritas.com,
       James.Bottomley@steeleye.com, rmk+lkml@arm.linux.org.uk,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Containment measures for slab objects on scatter gather
 lists
Message-ID: <20070629131657.5ecc3baa@the-village.bc.nu>
In-Reply-To: <20070628224519.1a3319c3.akpm@linux-foundation.org>
References: <Pine.LNX.4.64.0706282128570.11739@schroedinger.engr.sgi.com>
	<20070628.220606.112621271.davem@davemloft.net>
	<20070628222424.4cbae90c.akpm@linux-foundation.org>
	<20070628.223734.21928089.davem@davemloft.net>
	<20070628224519.1a3319c3.akpm@linux-foundation.org>
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> If those operations involve modifying that slab page's pageframe then what
> stops concurrent dma'ers from stomping on each other's changes?  As in:
> why aren't we already buggy?

Or DMA operations falling out with CPU operations in the same memory
area. Not all platforms have hardware consistency and some will blat the
entire page out of cache.

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