Exynos4-bus device devfreq driver add DVFS capability for
Exynos4210/4212/4412-Bus (memory). The driver monitors PPMU counters of memory
controllers and adjusts operating frequencies and voltages with OPP.
For Exynos4210, vdd_int is controlled. For exynos4412/4212, vdd_mif and
vdd_int are controlled.

Dependency (CONFIG_EXYNOS_ASV):
Exynos4 ASV driver has been posted in the mailing list; however, it
si not yet upstreamed. Although the current revision of Exynos4 ASV
patch does not contain "CONFIG_EXYNOS_ASV", we have added the symbol
to hide the dependent from compilers for now. As soon as Exynos4 ASV
drivers are merged, the #ifdef statement will be removed or the
name will be changed.

However, enabling ASV is essential in most Exynos4 chips to reduce
the power consumption of Exynos4210 because without ASV, this Devfreq
driver assumes the worst case scenario, which consumes more power.
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

---
Changes from v1
- Support 4212 and 4412 as well as 4210.

* git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-rc-fixes-2.6: (22 commits)
  [SCSI] fcoe: fix fcoe in a DCB environment by adding DCB notifiers to set skb priority
  [SCSI] bnx2i: Fixed kernel panic caused by unprotected task->sc->request deref
  [SCSI] qla4xxx: check for failed conn setup
  [SCSI] qla4xxx: a small loop fix
  [SCSI] qla4xxx: fix flash/ddb support
  [SCSI] zfcp: return early from slave_destroy if slave_alloc returned early
  [SCSI] fcoe: Fix preempt count leak in fcoe_filter_frames()
  [SCSI] qla2xxx: Update version number to 8.03.07.12-k.
  [SCSI] qla2xxx: Submit all chained IOCBs for passthrough commands on request queue 0.
  [SCSI] qla2xxx: Correct fc_host port_state display.
  [SCSI] qla2xxx: Disable generating pause frames when firmware hang detected for ISP82xx.
  [SCSI] qla2xxx: Clear mailbox busy flag during premature mailbox completion for ISP82xx.
  [SCSI] qla2xxx: Encapsulate prematurely completing mailbox commands during ISP82xx firmware hang.
  [SCSI] qla2xxx: Display IPE error message for ISP82xx.
  [SCSI] qla2xxx: Return the correct value for a mailbox command if 82xx is in reset recovery.
  [SCSI] qla2xxx: Enable Minidump by default with default capture mask 0x1f.
  [SCSI] qla2xxx: Stop unconditional completion of mailbox commands issued in interrupt mode during firmware hang.
  [SCSI] qla2xxx: Revert back the request queue mapping to request queue 0.
  [SCSI] qla2xxx: Don't call alloc_fw_dump for ISP82XX.
  [SCSI] qla2xxx: Check for SCSI status on underruns.
  ...

* 'for-linus/i2c-32-rc6' of git://git.fluff.org/bjdooks/linux:
  i2c-eg20t: correct the driver init order of pch_i2c_probe()
  I2C: OMAP: fix FIFO usage for OMAP4
  i2c-s3c2410: Fix return code of s3c24xx_i2c_parse_dt_gpio
  i2c: i2c-s3c2410: Add a cpu_relax() to busy wait for bus idle

I noticed that hotplug of one setup does not work with recent change in
pci tree.

After checking the bridge conf setup, I noticed that the bridges get
assigned but do not get enabled.

The reason is the following commit, while simply ignores bridge
resources when enabling a pci device:

| commit bbef98ab
| Author: Ram Pai <linuxram@us.ibm.com>
| Date:   Sun Nov 6 10:33:10 2011 +0800
|
|    PCI: defer enablement of SRIOV BARS
|...
|    NOTE: Note, there is subtle change in the pci_enable_device() API.  Any
|    driver that depends on SRIOV BARS to be enabled in pci_enable_device()
|    can fail.

Put back bridge resource and ROM resource checking to fix the problem.

That should fix regression like BIOS does not assign correct resource to
bridge.

Discussion can be found at:
	http://www.spinics.net/lists/linux-pci/msg12874.htmlSigned-off-by: Yinghai Lu <yinghai@kernel.org>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Before registering an adapter to i2c subsystem, we need make sure
driver is ready for incoming i2c xfer, becasue the i2c_add_adapter()
may trigger a i2c device driver's proble function which may start
some real i2c xfer. I met this issue when integrating a TSC2007 i2c
touch screen device with the i2c-eg20t driver.

This patch will call request_irq() and hw init before calling
i2c_add_adapter().
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

Currently the fifo depth is set to zero for OMAP4 which disables
the FIFO usage. This patch enables the FIFO usage for I2C transactions
on OMAP4 also.

Tested on omap4430 and 3430.
Tested-and-Reported-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

s3c24xx_i2c_parse_dt_gpio is called when cfg_gpio is not defined
in the platform data of the i2c device. When DT is not enabled,
the above function always returns -EINVAL. Since there can be
some i2c devices which don't need to configure any gpio lines,
the probe of such devices would fail here. Changing the default
return value to success would fix this issue.
Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

Be a bit more friendly.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

Merge branches 'perf-urgent-for-linus' and 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf events: Fix ring_buffer_wakeup() brown paperbag bug

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Fix select_idle_sibling() regression in selecting an idle SMT sibling
  MAINTAINERS: Update tip.git related git trees

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci:
  PCI: Set device power state to PCI_D0 for device without native PM support
  PCI hotplug: Always allow acpiphp to handle non-PCIe bridges
  PCI: fix ats compile failure
  PCI: defer enablement of SRIOV BARS

This reverts commit eb1711bb.

It blows up the i915 seqno tracking, resulting in the

	BUG_ON(seqno == 0);

in i915_wait_request() triggering, which will cause lock-ups.

See for example
  https://bugs.launchpad.net/ubuntu/+source/linux/+bug/903010
  https://lkml.org/lkml/2011/12/14/395Reported-requested-and-tested-by: Dirk Hohndel <dirk@hohndel.org>
Reported-by: Richard Eames <Richard.Eames@flinders.edu.au>
Reported-by: Rocko Requin <rockorequin@hotmail.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Keith Packard <keithp@keithp.com>
Cc: Eric Anholt <eric@anholt.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc:
  sparc32: Be less strict in matching %lo part of relocation.
  sbus: convert drivers/sbus/char/* to use module_platform_driver()
  bbc_i2c: Remove unneeded err variable
  sparc: Use kmemdup rather than duplicating its implementation

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net:
  ipv6: Check dest prefix length on original route not copied one in rt6_alloc_cow().
  sch_gred: should not use GFP_KERNEL while holding a spinlock
  ipip, sit: copy parms.name after register_netdevice
  ipv6: Fix for adding multicast route for loopback device automatically.
  ssb: fix init regression with SoCs
  rtl8192{ce,cu,de,se}: avoid problems because of possible ERFOFF -> ERFSLEEP transition
  mac80211: fix another race in aggregation start
  fsl_pq_mdio: Clean up tbi address configuration
  ppp: fix pptp double release_sock in pptp_bind()
  net/fec: fix the use of pdev->id
  ath9k: fix check for antenna diversity support
  batman-adv: delete global entry in case of roaming
  batman-adv: in case of roaming mark the client with TT_CLIENT_ROAM
  Bluetooth: Correct version check in hci_setup
  btusb: fix a memory leak in btusb_send_frame()
  Bluetooth: bnep: Fix module reference
  Bluetooth: cmtp: Fix module reference
  Bluetooth: btmrvl: support Marvell Bluetooth device SD8797

Merge branches 'for-linus' and 'for-linus-3.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
  Btrfs: unplug every once and a while
  Btrfs: deal with NULL srv_rsv in the delalloc inode reservation code
  Btrfs: only set cache_generation if we setup the block group
  Btrfs: don't panic if orphan item already exists
  Btrfs: fix leaked space in truncate
  Btrfs: fix how we do delalloc reservations and how we free reservations on error
  Btrfs: deal with enospc from dirtying inodes properly
  Btrfs: fix num_workers_starting bug and other bugs in async thread
  BTRFS: Establish i_ops before calling d_instantiate
  Btrfs: add a cond_resched() into the worker loop
  Btrfs: fix ctime update of on-disk inode
  btrfs: keep orphans for subvolume deletion
  Btrfs: fix inaccurate available space on raid0 profile
  Btrfs: fix wrong disk space information of the files
  Btrfs: fix wrong i_size when truncating a file to a larger size
  Btrfs: fix btrfs_end_bio to deal with write errors to a single mirror

* 'for-linus-3.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
  btrfs: lower the dirty balance poll interval

* 'drm-intel-fixes' of git://people.freedesktop.org/~keithp/linux:
  drm/i915/dp: Dither down to 6bpc if it makes the mode fit
  drm/i915: enable semaphores on per-device defaults
  drm/i915: don't set unpin_work if vblank_get fails
  drm/i915: By default, enable RC6 on IVB and SNB when reasonable
  iommu: Export intel_iommu_enabled to signal when iommu is in use
  drm/i915/sdvo: Include LVDS panels for the IS_DIGITAL check
  drm/i915: prevent division by zero when asking for chipset power
  drm/i915: add PCH info to i915_capabilities
  drm/i915: set the right SDVO transcoder for CPT
  drm/i915: no-lvds quirk for ASUS AT5NM10T-I
  drm/i915: Treat pre-gen4 backlight duty cycle value consistently
  drm/i915: Hook up Ivybridge eDP
  drm/i915: add multi-threaded forcewake support

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound:
  ALSA: HDA: Use LPIB Position fix for Intel SCH Poulsbo
  ALSA: hda: fix mute led polarity for HP laptops with buggy BIOS
  ALSA: HDA: Set position fix to LPIB for an Atom/Poulsbo based device
  ASoC: Fix hx4700 error handling to free gpios if snd_soc_register_card fails
  ASoC: WM8958: correctly show firmware magic on mismatch
  ASoC: mxs: Add appropriate MODULE_ALIAS()
  ASoC: mxs: Add missing MODULE_LICENSE("GPL")
  ASoC: Fix WM8996 24.576MHz clock operation
  ASoC: Include linux/module.h for smdk2443_wm9710
  ASoC: Fix a typo in jive_wm8750
  ASoC: Fix build dependency for SND_SOC_JZ4740_CODEC
  ASoC: Include linux/io.h for jz4740 codec

* 'gpio/merge' of git://git.secretlab.ca/git/linux-2.6:
  gpio: Fix DA9052 GPIO build errors.
  gpio: mpc8xxx: don't allow input-only pins to be output for MPC5121
  gpio-ml-ioh: Add the irq_disable/irq_enable hooks for ml-ioh irq chip
  gpio-ml-ioh: fix a bug in the interrupt handler
  gpio: pl061: drop extra check for NULL platform_data

* 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc:
  ARM: OMAP: rx51: fix USB
  ARM: OMAP: mcbsp: Fix possible memory corruption
  arm/imx: fix power button on imx51 babbage board
  ARM: imx: fix cpufreq build errors
  ARM: mx5: add __initconst for fec pdata
  MXC PWM: should active during DOZE/WAIT/DBG mode
  ARM: EXYNOS: Fix build error without CONFIG_LOCAL_TIMERS
  ARM: EXYNOS: Fix for stall in case of cpu hotplug or sleep
  ARM: S5PV210: Set 1000ns as PWM backlight period on SMDKV210
  ARM: SAMSUNG: remove duplicated header include

* 'for-linus' of git://git.kernel.dk/linux-block:
  block: don't kick empty queue in blk_drain_queue()
  block/swim3: Locking fixes
  loop: Fix discard_alignment default setting
  cfq-iosched: fix cfq_cic_link() race confition
  cfq-iosched: free cic_index if blkio_alloc_blkg_stats fails
  cciss: fix flush cache transfer length
  cciss: Add IRQF_SHARED back in for the non-MSI(X) interrupt handler
  loop: fix loop block driver discard and encryption comment
  block: initialize request_queue's numa node during

Tests show that the original large intervals can easily make the dirty
limit exceeded on 100 concurrent dd's. So adapt to as large as the
next check point selected by the dirty throttling algorithm.
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

Some active adaptors (VGA usually) only have two lanes at 2.7GHz.
That's a maximum pixel clock of 144MHz at 8bpc, but 192MHz at 6bpc.

Fixes Asus UX31 panel being black at startup due to no valid modes since
dc22ee6f.

v2: Rebased to current code, resulting in the fix applying to EDP panels as
    well.  Also changed from spatio-temporal to just spatial dithering on
    pre-ironlake, to be conssitent (and less visual flicker)
Signed-off-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Tested-by: Eric Anholt <eric@anholt.net>
Tested-by: Dirk Hohndel <hohndel@infradead.org>
Signed-off-by: Keith Packard <keithp@keithp.com>

This adds a default setting for semaphores parameter, and enables
semaphores by default on IVB.

For now, as semaphores interaction with VTd causes random issues on
SNB, we do not enable them by default. But they can still be enabled
via the semaphores=1 kernel parameter.

v2: enables semaphores on SNB when IO remapping is disabled, with base
on Keith Packard patch.

CC: Daniel Vetter <daniel.vetter@ffwll.ch>
CC: Ben Widawsky <ben@bwidawsk.net>
CC: Keith Packard <keithp@keithp.com>
CC: Jesse Barnes <jbarnes@virtuousgeek.org>
CC: Chris Wilson <chris@chris-wilson.co.uk>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=42696
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=40564
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=41353
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38862Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

This fixes a race where we may try to finish a page flip and decrement
the refcount even if our vblank_get failed and we ended up with a
spurious flip pending interrupt.

Fixes https://bugs.freedesktop.org/show_bug.cgi?id=34211.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Keith Packard <keithp@keithp.com>

RC6 should always work on IVB, and should work on SNB whenever IO
remapping is disabled. RC6 never works on Ironlake. Make the default
value for the parameter follow these guidelines. Setting the value
to either 0 or 1 will force the specified behavior.
Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38567
Cc: Ted Phelps <phelps@gnusto.com>
Cc: Peter <pab1612@gmail.com>
Cc: Lukas Hejtmanek <xhejtman@fi.muni.cz>
Cc: Andrew Lutomirski <luto@mit.edu>

In i915 driver, we do not enable either rc6 or semaphores on SNB when dmar
is enabled. The new 'intel_iommu_enabled' variable signals when the
iommu code is in operation.

Cc: Ted Phelps <phelps@gnusto.com>
Cc: Peter <pab1612@gmail.com>
Cc: Lukas Hejtmanek <xhejtman@fi.muni.cz>
Cc: Andrew Lutomirski <luto@mit.edu>
CC: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

We were checking whether the supplied edid matched the connector it was
read from. We do this in case a DDC read returns an EDID for another
device on a multifunction or otherwise interesting card. However, we
failed to include LVDS as a digital device and so rejecting an otherwise
valid EDID.

Fixes the detection of the secondary SDVO LVDS panel on the Libretto
W105.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=39216Signed-off-by: Keith Packard <keithp@keithp.com>

This prevents an in-kernel division by zero which happens when we are
asking for i915_chipset_val too quickly, or within a race condition
between the power monitoring thread and userspace accesses via debugfs.

The issue can be reproduced easily via the following command:
while ``; do cat /sys/kernel/debug/dri/0/i915_emon_status; done

This is particularly dangerous because it can be triggered by
a non-privileged user by just reading the debugfs entry.

This issue was also found independently by Konstantin Belousov
<kostikbel@gmail.com>, who proposed a similar patch.
Reported-by: Konstantin Belousov <kostikbel@gmail.com>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Acked-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Eugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

v2: add a CPT-specific macro, make code cleaner
v3: fix commit message

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=41272
Cc: stable@kernel.org
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Keith Packard <keithp@keithp.com>

https://bugzilla.redhat.com/show_bug.cgi?id=750006Signed-off-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

Mike Galbraith reported that this recent commit:

   commit 4dcfe102
   Author: Peter Zijlstra <peterz@infradead.org>
   Date:   Thu Nov 10 13:01:10 2011 +0100

       sched: Avoid SMT siblings in select_idle_sibling() if possible

stopped selecting an idle SMT sibling when there are no idle
cores in a single socket system.

Intent of the select_idle_sibling() was to fallback to an idle
SMT sibling, if it fails to identify an idle core. But this
fallback was not happening on systems where all the scheduler
domains had `SD_SHARE_PKG_RESOURCES' flag set.

Fix it. Slightly bigger patch of cleaning all these goto's etc
is queued up for the next release.
Reported-by: Mike Galbraith <efault@gmx.de>
Reported-by: Alex Shi <alex.shi@intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1323978421.1984.244.camel@sbsiddha-desk.sc.intel.comSigned-off-by: Ingo Molnar <mingo@elte.hu>

Merge branch 'samsung-fixes-3' of git://git.kernel.org/pub/scm/linux/kernel/git/kgene/linux-samsung into fixes

* 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/ibft:
  ibft: Fix finding IBFT ACPI table on UEFI

* 'staging-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
  staging: r8712u: Add new USB ID
  staging: tidspbridge: request dmtimer clocks on init
  staging: tidspbridge: include module.h by default

* 'usb-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
  USB: option: Removing one bogus and adding some new Huawei combinations
  USB: cdc-acm: add IDs for Motorola H24 HSPA USB module.
  usb: option: Add Huawei E398 controlling interfaces
  usb: renesas_usbhs: add hcd->has_tt for low/full speed
  usb: renesas_usbhs: typofix: irq_dtch control DTCHE
  usb: gadget: storage: release superspeed descriptors.

The bisection implemented in unwind_find_origin() stopped to early.  If
there is only a single entry left to check the original code just took
the end point as origin which might be wrong.

This was introduced in commit de66a979 ("ARM: 7187/1: fix unwinding
for XIP kernels").
Reported-and-tested-by: Nick Bowler <nbowler@elliptictech.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The btrfs io submission threads can build up massive plug lists.  This
keeps things more reasonable so we don't hand over huge dumps of IO at
once.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

While probing, fd sets up queue, probes hardware and tears down the
queue if probing fails.  In the process, blk_drain_queue() kicks the
queue which failed to finish initialization and fd is unhappy about
that.

  floppy0: no floppy controllers found
  ------------[ cut here ]------------
  WARNING: at drivers/block/floppy.c:2929 do_fd_request+0xbf/0xd0()
  Hardware name: To Be Filled By O.E.M.
  VFS: do_fd_request called on non-open device
  Modules linked in:
  Pid: 1, comm: swapper Not tainted 3.2.0-rc4-00077-g5983fe2b #2
  Call Trace:
   [<ffffffff81039a6a>] warn_slowpath_common+0x7a/0xb0
   [<ffffffff81039b41>] warn_slowpath_fmt+0x41/0x50
   [<ffffffff813d657f>] do_fd_request+0xbf/0xd0
   [<ffffffff81322b95>] blk_drain_queue+0x65/0x80
   [<ffffffff81322c93>] blk_cleanup_queue+0xe3/0x1a0
   [<ffffffff818a809d>] floppy_init+0xdeb/0xe28
   [<ffffffff818a72b2>] ? daring+0x6b/0x6b
   [<ffffffff810002af>] do_one_initcall+0x3f/0x170
   [<ffffffff81884b34>] kernel_init+0x9d/0x11e
   [<ffffffff810317c2>] ? schedule_tail+0x22/0xa0
   [<ffffffff815dbb14>] kernel_thread_helper+0x4/0x10
   [<ffffffff81884a97>] ? start_kernel+0x2be/0x2be
   [<ffffffff815dbb10>] ? gs_change+0xb/0xb

Avoid it by making blk_drain_queue() kick queue iff dispatch queue has
something on it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Ralf Hildebrandt <Ralf.Hildebrandt@charite.de>
Reported-by: Wu Fengguang <fengguang.wu@intel.com>
Tested-by: Sergei Trofimovich <slyich@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>