linux-kernel - Re: [PATCH v2] mm: dmapool: use provided gfp flags for all dma_alloc

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Date:	Tue, 15 Jan 2013 09:50:20 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Jason Cooper <jason@...edaemon.net>
Cc:	Soeren Moch <smoch@....de>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Andrew Lunn <andrew@...n.ch>, Arnd Bergmann <arnd@...db.de>,
	Michal Hocko <mhocko@...e.cz>, linux-kernel@...r.kernel.org,
	linaro-mm-sig@...ts.linaro.org, linux-mm@...ck.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	linux-arm-kernel@...ts.infradead.org,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH v2] mm: dmapool: use provided gfp flags for all
 dma_alloc_coherent() calls

On Tue, Jan 15, 2013 at 11:56:42AM -0500, Jason Cooper wrote:
> Greg,
> 
> I've added you to the this thread hoping for a little insight into USB
> drivers and their use of coherent and GFP_ATOMIC.  Am I barking up the
> wrong tree by looking a the drivers?

I don't understand, which drivers are you referring to?  USB host
controller drivers, or the "normal" drivers?  Most USB drivers use
GFP_ATOMIC if they are creating memory during their URB callback path,
as that is interrupt context.  But it shouldn't be all that bad, and the
USB core hasn't changed in a while, so something else must be causing
this.

greg k-h
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