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Jon Hunter 9743a3b62d of: dma: fix protection of DMA controller data stored by DMA helpers 
In the current implementation of the OF DMA helpers, read-copy-update (RCU)
linked lists are being used for storing and accessing the DMA controller data.
This part of implementation is based upon V2 of the DMA helpers by Nicolas [1].
During a recent review of RCU, it became apparent that the code is missing the
required rcu_read_lock()/unlock() calls as well as synchronisation calls before
freeing any memory protected by RCU.

Having looked into adding the appropriate RCU calls to protect the DMA data it
became apparent that with the current DMA helper implementation, using RCU is
not as attractive as it may have been before. The main reasons being that ...

1. We need to protect the DMA data around calls to the xlate function.
2. The of_dma_simple_xlate() function calls the DMA engine function
   dma_request_channel() which employs a mutex and so could sleep.
3. The RCU read-side critical sections must not sleep and so we cannot hold
   an RCU read lock around the xlate function.

Therefore, instead of using RCU, an alternative for this use-case is to employ
a simple spinlock inconjunction with a usage count variable to keep track of
how many current users of the DMA data structure there are. With this
implementation, the DMA data cannot be freed until all current users of the
DMA data are finished.

This patch is based upon the DMA helpers fix for potential deadlock [2].

[1] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[2] http://marc.info/?l=linux-arm-kernel&m=134859982520984&w=2

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2013-01-07 22:05:01 -08:00
..
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acpi Merge branch 'x86-acpi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-12-14 10:03:23 -08:00
amba Merge tag 'tegra-for-3.8-fixes-for-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/swarren/linux-tegra into fixes 2012-12-17 10:04:27 -08:00
ata 1) More ACPI fixes 2012-12-15 12:37:18 -08:00
atm solos-pci: double lock in geos_gpio_store() 2012-12-21 13:14:00 -08:00
auxdisplay
base vfs: turn is_dir argument to kern_path_create into a lookup_flags arg 2012-12-20 18:50:02 -05:00
bcma MTD pull for 3.8 2012-12-19 12:47:41 -08:00
block Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client 2012-12-20 14:00:13 -08:00
bluetooth Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2012-12-12 18:07:07 -08:00
bus ARM: OMAP: Fix drivers to depend on omap for internal devices 2012-12-16 15:23:37 -08:00
cdrom
char Some nice cleanups, and even a patch my wife did as a "live" demo for 2012-12-20 08:37:05 -08:00
clk MTD pull for 3.8 2012-12-19 12:47:41 -08:00
clocksource ARM: arm-soc: Updates for Marvell mvebu/kirkwood 2012-12-14 14:54:26 -08:00
connector
cpufreq ACPI and power management updates for 3.8-rc1 2012-12-11 12:45:35 -08:00
cpuidle ARM: arm-soc: SoC updates for 3.8 2012-12-12 12:05:15 -08:00
crypto Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2012-12-18 09:58:09 -08:00
dca
devfreq Merge branch 'pm-devfreq' 2012-12-07 23:13:36 +01:00
dio
dma ioat: add missing DMA unmap to ioat_dma_self_test() 2013-01-07 22:04:58 -08:00
edac Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2012-12-14 14:27:45 -08:00
eisa
extcon
firewire Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2012-12-13 12:00:02 -08:00
firmware drivers/firmware/dmi_scan.c: fetch dmi version from SMBIOS if it exists 2012-12-20 17:40:19 -08:00
gpio gpio/mvebu-gpio: Make mvebu-gpio depend on OF_CONFIG 2012-12-19 22:15:14 +00:00
gpu Revert "drm: tegra: protect DC register access with mutex" 2012-12-30 21:58:20 +10:00
hid Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media 2012-12-13 19:22:22 -08:00
hsi
hv
hwmon hwmon: (emc6w201) Fix DIV_ROUND_CLOSEST problem with unsigned divisors 2012-12-22 02:16:40 -08:00
hwspinlock
i2c i2c: remove __dev* attributes from subsystem 2012-12-22 20:13:45 +01:00
ide
idle
iio This is the MFD patch set for the 3.8 merge window. 2012-12-16 18:55:20 -08:00
infiniband Second batch of InfiniBand/RDMA changes for 3.8: 2012-12-21 16:40:26 -08:00
input Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-12-19 12:56:42 -08:00
iommu IOMMU Updates for Linux v3.8 2012-12-20 10:07:25 -08:00
ipack TTY/Serial merge for 3.8-rc1 2012-12-11 14:08:47 -08:00
irqchip ARM: arm-soc: Device-tree updates, take 2 2012-12-14 14:42:53 -08:00
isdn mISDN: fix race in timer canceling on module unloading 2012-12-14 13:14:07 -05:00
leds leds: leds-gpio: set devm_gpio_request_one() flags param correctly 2013-01-02 17:58:41 -08:00
lguest lguest: fix typo 2012-12-18 15:19:06 +10:30
macintosh Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2012-12-18 09:58:09 -08:00
md Miscellaneous device-mapper fixes, cleanups and performance improvements. 2012-12-21 17:08:06 -08:00
media ARM: arm-soc: late cleanups for omap 2012-12-30 09:59:21 -08:00
memory
memstick
message drivers/message/fusion/mptscsih.c: missing break 2012-12-18 15:02:12 -08:00
mfd ARM: arm-soc fixes for 3.8 2012-12-20 07:21:54 -08:00
misc carma-fpga: pass correct flags to ->device_prep_dma_memcpy() 2013-01-07 22:05:00 -08:00
mmc This is the MFD patch set for the 3.8 merge window. 2012-12-16 18:55:20 -08:00
mtd mtd: fsmc_nand: add missing DMA unmap to dma_xfer() 2013-01-07 22:04:59 -08:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2012-12-27 10:40:30 -08:00
nfc
nubus
of of: dma: fix protection of DMA controller data stored by DMA helpers 2013-01-07 22:05:01 -08:00
oprofile
parisc
parport
pci PCI: Reduce Ricoh 0xe822 SD card reader base clock frequency to 50MHz 2012-12-26 10:43:06 -07:00
pcmcia ARM: arm-soc: Header cleanups 2012-12-12 11:45:16 -08:00
pinctrl pinctrl: exynos5440/samsung: Staticize pcfgs 2012-12-18 19:00:25 -08:00
platform Corentin has moved 2012-12-17 17:15:14 -08:00
pnp Driver core updates for 3.8-rc1 2012-12-11 13:13:55 -08:00
power ARM: arm-soc: late cleanups for omap 2012-12-30 09:59:21 -08:00
pps
ps3
ptp Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2012-12-12 18:07:07 -08:00
pwm pwm: Changes for v3.8-rc1 2012-12-19 08:19:07 -08:00
rapidio Driver core updates for 3.8-rc1 2012-12-11 13:13:55 -08:00
regulator Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2012-12-13 12:00:02 -08:00
remoteproc Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2012-12-13 12:00:02 -08:00
rpmsg virtio: rpmsg: make it clear that virtqueue_add_buf() no longer returns > 0 2012-12-18 15:20:36 +10:30
rtc revert "rtc: recycle id when unloading a rtc driver" 2012-12-20 17:40:20 -08:00
s390 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2012-12-13 14:20:19 -08:00
sbus
scsi Second batch of InfiniBand/RDMA changes for 3.8: 2012-12-21 16:40:26 -08:00
sfi
sh
sn
spi spi/sh-hspi: fix return value check in hspi_probe(). 2012-12-19 15:11:41 +00:00
ssb Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2012-12-14 14:27:45 -08:00
staging Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2012-12-17 15:44:47 -08:00
target Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending 2012-12-15 14:25:10 -08:00
tc
thermal Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2012-12-13 12:00:02 -08:00
tty Merge branch 'omap-for-v3.8/fixes-for-merge-window' into omap-for-v3.8/fixes-for-merge-window-v2 2012-12-16 11:28:10 -08:00
uio ARM: arm-soc: SoC updates for 3.8 2012-12-12 12:05:15 -08:00
usb usb: musb: use io{read,write}*_rep accessors 2012-12-17 17:15:13 -08:00
uwb
vfio vfio-pci: Enable device before attempting reset 2012-12-07 13:43:51 -07:00
vhost Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending 2012-12-15 14:25:10 -08:00
video backlight: locomolcd: fix checkpatch error and warning 2012-12-18 15:02:11 -08:00
virt Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2012-12-18 09:58:09 -08:00
virtio Some nice cleanups, and even a patch my wife did as a "live" demo for 2012-12-20 08:37:05 -08:00
vlynq
vme
w1 ARM: OMAP: Fix drivers to depend on omap for internal devices 2012-12-16 15:23:37 -08:00
watchdog watchdog: twl4030_wdt: add DT support 2013-01-02 12:07:05 +01:00
xen Feature: 2012-12-16 17:39:14 -08:00
zorro
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