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Date: Tue, 15 Jan 2013 09:50:20 -0800
From: Greg KH <gregkh@linuxfoundation.org>
To: Jason Cooper <jason@lakedaemon.net>
Cc: Soeren Moch <smoch@web.de>, Marek Szyprowski <m.szyprowski@samsung.com>,
        Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
        Andrew Lunn <andrew@lunn.ch>, Arnd Bergmann <arnd@arndb.de>,
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        linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org,
        Kyungmin Park <kyungmin.park@samsung.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@suse.de>, linux-arm-kernel@lists.infradead.org,
        Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Subject: Re: [PATCH v2] mm: dmapool: use provided gfp flags for all
 dma_alloc_coherent() calls
Message-ID: <20130115175020.GA3764@kroah.com>
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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