From: Dan Williams <dan.j.williams@intel.com>
Date: Tue, 21 Jan 2014 23:48:12 +0000 (-0800)
Subject: dma-debug: introduce debug_dma_assert_idle()
X-Git-Tag: v3.14-rc1~134^2~116
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0abdd7a81b7e3fd781d7fabcca49501852bba17e;p=pandora-kernel.git

dma-debug: introduce debug_dma_assert_idle()

Record actively mapped pages and provide an api for asserting a given
page is dma inactive before execution proceeds.  Placing
debug_dma_assert_idle() in cow_user_page() flagged the violation of the
dma-api in the NET_DMA implementation (see commit 77873803363c "net_dma:
mark broken").

The implementation includes the capability to count, in a limited way,
repeat mappings of the same page that occur without an intervening
unmap.  This 'overlap' counter is limited to the few bits of tag space
in a radix tree.  This mechanism is added to mitigate false negative
cases where, for example, a page is dma mapped twice and
debug_dma_assert_idle() is called after the page is un-mapped once.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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