This adds support for the VGA/LCD core available from OpenCores:
http://opencores.org/project,vga_lcd

The driver have been tested together with both OpenRISC and
ARM (socfpga) processors.
Signed-off-by: NStefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

Since commit 41702d9a ("logo.c: get rid of
mips_machgroup") there's no longer a need to include <asm/bootinfo.h> on
MIPS.
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Acked-by: NRalf Baechle <ralf@linux-mips.org>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

Static checkers complain that there are paths where "tga_type_name" can
be NULL.  I've re-arranged the code slightly so that's impossible.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

Sparse complains here:

	drivers/video/mmp/core.c:33:16:
		warning: Using plain integer as NULL pointer
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

We aren't holding the disp_lock so we shouldn't release it.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NHaojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

The CLCD driver is used on ARM reference models for ARMv8 so add ARM64
to the list of dependencies. The driver also has no build time dependencies
on ARM (stubs are provided for ARM-specific DMA functions in the code) so
make it available with COMPILE_TEST in order to maximise build coverage.
Signed-off-by: NMark Brown <broonie@linaro.org>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

Replace local macro TGA_BUS_PCI with PCI standard
marco dev_is_pci().
Signed-off-by: NYijing Wang <wangyijing@huawei.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

Documentation/fb/modedb.txt states that video=option should be
considered a global option. But video_setup and fb_get_options are not
coded that way. Instead its required to boot with video=driver:option to
set a given option in drvier.  This is cumbersome because it requires to
know in advance which driver will be active for a given board/kernel.

The following patch implements the documented catchall for the fbdev
drivers. It is now possible to boot with video=XxY without the need to
know the active driver in advance. The specific case it tries to fix is
syslinux in the SUSE installer which offers a menu to set a display
resolution. Right now this just appends the vga= option the kernel. But
in addition to vga= it should be possible to pass a generic video=XxY
for all framebuffer/drm drivers. With this change forcing a certain
window size of VM displays is now much easier.

Today the video= option is stored in a global fb_mode_option. But
unfortunately only drm uses it.

Note: this change introduces a small memleak if video=option is actually
used because fb_mode_option is const. Most drivers use strsep to get to
individual options. This could be fixed in a followup patch which always
releases the option string in every caller of fb_get_options.
Signed-off-by: NOlaf Hering <olaf@aepfle.de>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

arm64 is unlikely to have a VGA console and does not export screen_info
causing build failures if the driver is build, for example in all*config.
Add a dependency on !ARM64 to prevent this.

This list is getting quite long, it may be easier to depend on a symbol
which architectures that do support the driver can select.
Signed-off-by: NMark Brown <broonie@linaro.org>
[tomi.valkeinen@ti.com: moved && to first modified line]
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

No need to allocate the framebuffer from the atomic pool, we are not
in interrupt context. Adding GFP_KERNEL to the framebuffer allocation
allows to use the much bigger CMA pool to allocate the framebuffer.
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: linux-fbdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

kmemleak reported a memory leak as below.

unreferenced object 0xffff880036ca84c0 (size 16):
  comm "swapper/0", pid 1, jiffies 4294877407 (age 4434.633s)
  hex dump (first 16 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 ff ff  ................
  backtrace:
    [<ffffffff814ed01e>] kmemleak_alloc+0x4e/0xb0
    [<ffffffff8118913c>] __kmalloc+0x1fc/0x290
    [<ffffffff81302c9e>] bit_cursor+0x24e/0x6c0
    [<ffffffff812ff2f4>] fbcon_cursor+0x154/0x1d0
    [<ffffffff813675d8>] hide_cursor+0x28/0xa0
    [<ffffffff81368acf>] update_region+0x6f/0x90
    [<ffffffff81300268>] fbcon_switch+0x518/0x550
    [<ffffffff813695b9>] redraw_screen+0x189/0x240
    [<ffffffff8136a0e0>] do_bind_con_driver+0x360/0x380
    [<ffffffff8136a6e4>] do_take_over_console+0x114/0x1c0
    [<ffffffff812fdc83>] do_fbcon_takeover+0x63/0xd0
    [<ffffffff813023e5>] fbcon_event_notify+0x605/0x720
    [<ffffffff81501dcc>] notifier_call_chain+0x4c/0x70
    [<ffffffff81087f8d>] __blocking_notifier_call_chain+0x4d/0x70
    [<ffffffff81087fc6>] blocking_notifier_call_chain+0x16/0x20
    [<ffffffff812f201b>] fb_notifier_call_chain+0x1b/0x20

In this case ops->cursor_state.mask is allocated in bit_cursor() but
not freed in fbcon_exit(). So, fbcon_exit() needs to free buffer in its
process.
In the case, fbcon_exit() was called from fbcon_deinit() when driver
called remove_conflicting_framebuffers().
Signed-off-by: NMasami Ichikawa <masami256@gmail.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

Break out as soon as we find a mapped entry con2fb_map.
Signed-off-by: NWang YanQing <udknight@gmail.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

Currently the driver re-implements the code found in of_get_videomode()
except for the fact that the latter honors the 'native-mode' property
to select a spcific video timing from the list of possible timings.
The driver builds up a list of all video timings, but uses only the
last mode from the list anyway. While building the list it incorrectly
OR's the 'pixelclk-active' and 'de-active' flags of all modes into
single flags, possibly leading to a wrong pixelclock or data-enable
polarity setting.

Fix this by using the of_get_videomode() directly with the
OF_USE_NATIVE_MODE flag.

Since all current dts files only have one entry in their
display-timings node, this bug was not apparent and the fix does not
change the driver's behaviour for the current users.
Signed-off-by: NLothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

Make the messages that are printed in case of fatal errors actually
visible to the user without having to recompile the driver with
debugging enabled.
Signed-off-by: NLothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

The driver core clears the driver data to NULL after device_release
or on probe failure. Thus, it is not needed to manually clear the
device driver data to NULL.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

The driver core clears the driver data to NULL after device_release
or on probe failure. Thus, it is not needed to manually clear the
device driver data to NULL.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

The driver core clears the driver data to NULL after device_release
or on probe failure. Thus, it is not needed to manually clear the
device driver data to NULL.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

The driver core clears the driver data to NULL after device_release
or on probe failure. Thus, it is not needed to manually clear the
device driver data to NULL.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

This fixes a sparse warning.

Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: linux-fbdev@vger.kernel.org
Signed-off-by: NLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>

Commit "drm/ttm: Don't move non-existing data" didn't take the
swapped-out corner case into account. This patch corrects that.
Fixes blank screen after attempted suspend / hibernate on vmwgfx.
Signed-off-by: NThomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Fix build error: qxl uses crc32 functions so it needs to select
CRC32.

Also use angle quotes around a kernel header file name.

drivers/built-in.o: In function `qxl_display_read_client_monitors_config':
(.text+0x19d754): undefined reference to `crc32_le'
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NDave Airlie <airlied@redhat.com>

This patch adds support for RAPL on Intel ValleyView based SoC
platforms, such as Baytrail.

Besides adding CPU ID, special energy unit encoding is handled
for ValleyView.
Signed-off-by: NJacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

When configuring a default governor (via CONFIG_CPU_FREQ_DEFAULT_*) with the
intel_pstate driver, the desired default policy is not properly set. For
example, setting 'CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE' ends up with the
'powersave' policy being set.

Fix by configuring the correct default policy, if either 'powersave' or
'performance' are requested. Otherwise, fallback to what the driver originally
set via its 'init' routine.
Signed-off-by: NJason Baron <jbaron@akamai.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

There are cases where cpufreq_add_dev() may fail for some CPUs
during system resume. With the current code we will still have
sysfs cpufreq files for those CPUs and struct cpufreq_policy
would be already freed for them. Hence any operation on those
sysfs files would result in kernel warnings.

Example of problems resulting from resume errors (from Bjørn Mork):

WARNING: CPU: 0 PID: 6055 at fs/sysfs/file.c:343 sysfs_open_file+0x77/0x212()
missing sysfs attribute operations for kobject: (null)
Modules linked in: [stripped as irrelevant]
CPU: 0 PID: 6055 Comm: grep Tainted: G      D      3.13.0-rc2 #153
Hardware name: LENOVO 2776LEG/2776LEG, BIOS 6EET55WW (3.15 ) 12/19/2011
 0000000000000009 ffff8802327ebb78 ffffffff81380b0e 0000000000000006
 ffff8802327ebbc8 ffff8802327ebbb8 ffffffff81038635 0000000000000000
 ffffffff811823c7 ffff88021a19e688 ffff88021a19e688 ffff8802302f9310
Call Trace:
 [<ffffffff81380b0e>] dump_stack+0x55/0x76
 [<ffffffff81038635>] warn_slowpath_common+0x7c/0x96
 [<ffffffff811823c7>] ? sysfs_open_file+0x77/0x212
 [<ffffffff810386e3>] warn_slowpath_fmt+0x41/0x43
 [<ffffffff81182dec>] ? sysfs_get_active+0x6b/0x82
 [<ffffffff81182382>] ? sysfs_open_file+0x32/0x212
 [<ffffffff811823c7>] sysfs_open_file+0x77/0x212
 [<ffffffff81182350>] ? sysfs_schedule_callback+0x1ac/0x1ac
 [<ffffffff81122562>] do_dentry_open+0x17c/0x257
 [<ffffffff8112267e>] finish_open+0x41/0x4f
 [<ffffffff81130225>] do_last+0x80c/0x9ba
 [<ffffffff8112dbbd>] ? inode_permission+0x40/0x42
 [<ffffffff81130606>] path_openat+0x233/0x4a1
 [<ffffffff81130b7e>] do_filp_open+0x35/0x85
 [<ffffffff8113b787>] ? __alloc_fd+0x172/0x184
 [<ffffffff811232ea>] do_sys_open+0x6b/0xfa
 [<ffffffff811233a7>] SyS_openat+0xf/0x11
 [<ffffffff8138c812>] system_call_fastpath+0x16/0x1b

To fix this, remove those sysfs files or put the associated kobject
in case of such errors. Also, to make it simple, remove the cpufreq
sysfs links from all the CPUs (except for the policy->cpu) during
suspend, as that operation won't result in a loss of sysfs file
permissions and we can create those links during resume just fine.

Fixes: 5302c3fb ("cpufreq: Perform light-weight init/teardown during suspend/resume")
Reported-and-tested-by: NBjørn Mork <bjorn@mork.no>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Cc: 3.12+ <stable@vger.kernel.org> # 3.12+
[rjw: Changelog]
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

In the case of both the submit_queues param and use_per_node_hctx param
are used. We limit the number af submit_queues to the number of online
nodes.

If the submit_queues is a multiple of nr_online_nodes, its trivial. Simply map
them to the nodes. For example: 8 submit queues are mapped as node0[0,1],
node1[2,3], ...
If uneven, we are left with an uneven number of submit_queues that must be
mapped. These are mapped toward the first node and onward. E.g. 5
submit queues mapped onto 4 nodes are mapped as node0[0,1], node1[2], ...
Signed-off-by: NMatias Bjorling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The defaults for the module is to instantiate itself with blk-mq and a
submit queue for each CPU node in the system.

To save resources, initialize instead with a single submit queue.
Signed-off-by: NMatias Bjorling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Some pstore backing devices use on board flash as persistent
storage. These have limited numbers of write cycles so it
is a poor idea to use them from high frequency operations.
Signed-off-by: NTony Luck <tony.luck@intel.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch adds a check on the output buffer with access_ok(VERIFY_WRITE, ...)
to ensure the whole buffer is in userspace memory before using the
pointer in uverbs functions.  If the buffer or a subset of it is not
valid, returns -EFAULT to the caller.

This will also catch invalid buffer before the final call to
copy_to_user() which happen late in most uverb functions.

Just like the check in read(2) syscall, it's a sanity check to detect
invalid parameters provided by userspace. This particular check was added
in vfs_read() by Linus Torvalds for v2.6.12 with following commit message:

https://git.kernel.org/cgit/linux/kernel/git/tglx/history.git/commit/?id=fd770e66c9a65b14ce114e171266cf6f393df502

  Make read/write always do the full "access_ok()" tests.

  The actual user copy will do them too, but only for the
  range that ends up being actually copied. That hides
  bugs when the range has been clamped by file size or other
  issues.

Note: there's no need to check input buffer since vfs_write() already does
access_ok(VERIFY_READ, ...) as part of write() syscall.

Link: http://marc.info/?i=cover.1387273677.git.ydroneaud@opteya.comSigned-off-by: NYann Droneaud <ydroneaud@opteya.com>
Signed-off-by: NRoland Dreier <roland@purestorage.com>

Since ib_copy_from_udata() doesn't check yet the available input data
length before accessing userspace memory, an explicit check of this
length is required to prevent:

- reading past the user provided buffer,
- underflow when subtracting the expected command size from the input
  length.

This will ensure the newly added flow steering uverbs don't try to
process truncated commands.

Link: http://marc.info/?i=cover.1386798254.git.ydroneaud@opteya.com>
Signed-off-by: NYann Droneaud <ydroneaud@opteya.com>
Signed-off-by: NRoland Dreier <roland@purestorage.com>

If the flow_spec items parsed count does not match the number of items
declared in the flow_attr command, or if not all bytes are used for
flow_spec items (eg. trailing garbage), a log message is reported and
the function leave through the error path. Unfortunately the error
code is currently not set.

This patch set error code to -EINVAL in such cases, so that the error
is reported to userspace instead of silently fail.

Link: http://marc.info/?i=cover.1386798254.git.ydroneaud@opteya.com>
Signed-off-by: NYann Droneaud <ydroneaud@opteya.com>
Signed-off-by: NRoland Dreier <roland@purestorage.com>

As noted by Daniel Vetter in its article "Botching up ioctls"[1]

  "Check *all* unused fields and flags and all the padding for whether
   it's 0, and reject the ioctl if that's not the case.  Otherwise
   your nice plan for future extensions is going right down the
   gutters since someone *will* submit an ioctl struct with random
   stack garbage in the yet unused parts. Which then bakes in the ABI
   that those fields can never be used for anything else but garbage."

It's important to ensure that reserved fields are set to known value,
so that it will be possible to use them latter to extend the ABI.

The same reasonning apply to comp_mask field present in newer uverbs
command: per commit 22878dbc ("IB/core: Better checking of
userspace values for receive flow steering"), unsupported values in
comp_mask are rejected.

[1] http://blog.ffwll.ch/2013/11/botching-up-ioctls.html

Link: http://marc.info/?i=cover.1386798254.git.ydroneaud@opteya.com>
Signed-off-by: NYann Droneaud <ydroneaud@opteya.com>
Signed-off-by: NRoland Dreier <roland@purestorage.com>

Just like the check added to create_flow in 22878dbc ("IB/core:
Better checking of userspace values for receive flow steering"),
comp_mask must be checked in destroy_flow too.

Since only empty comp_mask is currently supported, any other value
must be rejected.

This check was silently added in a previous patch[1] to move comp_mask
in extended command header, part of previous patchset[2] against
create/destroy_flow uverbs. The idea of moving comp_mask to the header
was discarded for the final patchset[3].

Unfortunately the check added in destroy_flow uverb was not integrated
in the final patchset.

[1] http://marc.info/?i=40175eda10d670d098204da6aa4c327a0171ae5f.1381510045.git.ydroneaud@opteya.com
[2] http://marc.info/?i=cover.1381510045.git.ydroneaud@opteya.com
[3] http://marc.info/?i=cover.1383773832.git.ydroneaud@opteya.com

Cc: Matan Barak <matanb@mellanox.com>
Link: http://marc.info/?i=cover.1386798254.git.ydroneaud@opteya.com>
Signed-off-by: NYann Droneaud <ydroneaud@opteya.com>
Signed-off-by: NRoland Dreier <roland@purestorage.com>

As noted by Daniel Vetter in its article "Botching up ioctls"[1]

  "Check *all* unused fields and flags and all the padding for whether
   it's 0, and reject the ioctl if that's not the case.  Otherwise
   your nice plan for future extensions is going right down the
   gutters since someone *will* submit an ioctl struct with random
   stack garbage in the yet unused parts. Which then bakes in the ABI
   that those fields can never be used for anything else but garbage."

It's important to ensure that reserved fields are set to known value,
so that it will be possible to use them latter to extend the ABI.

The same reasonning apply to comp_mask field present in newer uverbs
command: per commit 22878dbc ("IB/core: Better checking of
userspace values for receive flow steering"), unsupported values in
comp_mask are rejected.

[1] http://blog.ffwll.ch/2013/11/botching-up-ioctls.html

Link: http://marc.info/?i=cover.1386798254.git.ydroneaud@opteya.com>
Signed-off-by: NYann Droneaud <ydroneaud@opteya.com>
Signed-off-by: NRoland Dreier <roland@purestorage.com>

Trying to have a ternary operator to choose between NULL (or 0) and the
real pointer value in invocations leads to an impossible choice between
a sparse error about a literal 0 used as a NULL pointer, and a gcc
warning about "pointer/integer type mismatch in conditional expression."

Rather than clutter the source with more casts, move the ternary
operator into a new INIT_UDATA_BUF_OR_NULL() macro, which makes it
easier to use and simplifies its callers.
Reported-by: NYann Droneaud <ydroneaud@opteya.com>
Signed-off-by: NRoland Dreier <roland@purestorage.com>

Fixes gfx corruption on certain TN/RL parts.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=60389Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

This patch fixes a possible scsi_host reference leak in qlt_lport_register(),
when a non zero return from the passed (*callback) does not call drop the
local reference via scsi_host_put() before returning.

This currently does not effect existing tcm_qla2xxx code as the passed callback
will never fail, but fix this up regardless for future code.

Cc: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

lun->lun_ref is also initialized in core_tpg_post_addlun, so it doesn't
need to be done in core_tpg_setup_virtual_lun0.

(nab: Drop left-over percpu_ref_cancel_init in failure path)
Signed-off-by: NAndy Grover <agrover@redhat.com>
Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>

Commit 7ea6c6c1 ("Move cper.c from drivers/acpi/apei to
drivers/firmware/efi") results in CONFIG_EFI being enabled even
when the user doesn't want this. Since ACPI APEI used to build
fine without UEFI (and as far as I know also has no functional
depency on it), at least in that case using a reverse dependency
is wrong (and a straight one isn't needed).

Whether the same is true for ACPI_EXTLOG I don't know - if there
is a functional dependency, it should depend on EFI rather than
selecting it. It certainly has (currently) no build dependency.

Adjust Kconfig and build logic so that the bad dependency gets
avoided.
Signed-off-by: NJan Beulich <jbeulich@suse.com>
Acked-by: NTony Luck <tony.luck@intel.com>
Cc: Matt Fleming <matt.fleming@intel.com>
Link: http://lkml.kernel.org/r/52AF1EBC020000780010DBF9@nat28.tlf.novell.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Linux 3.10 changed the timing of how thread_info->flags is touched:

	x86: Use generic idle loop
	(7d1a9417)

This caused Intel NHM-EX and WSM-EX servers to experience a large number
of immediate MONITOR/MWAIT break wakeups, which caused cpuidle to demote
from deep C-states to shallow C-states, which caused these platforms
to experience a significant increase in idle power.

Note that this issue was already present before the commit above,
however, it wasn't seen often enough to be noticed in power measurements.

Here we extend an errata workaround from the Core2 EX "Dunnington"
to extend to NHM-EX and WSM-EX, to prevent these immediate
returns from MWAIT, reducing idle power on these platforms.

While only acpi_idle ran on Dunnington, intel_idle
may also run on these two newer systems.
As of today, there are no other models that are known
to need this tweak.

Link: http://lkml.kernel.org/r/CAJvTdK=%2BaNN66mYpCGgbHGCHhYQAKx-vB0kJSWjVpsNb_hOAtQ@mail.gmail.comSigned-off-by: NLen Brown <len.brown@intel.com>
Link: http://lkml.kernel.org/r/baff264285f6e585df757d58b17788feabc68918.1387403066.git.len.brown@intel.com
Cc: <stable@vger.kernel.org> # 3.12.x, 3.11.x, 3.10.x
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Freezable kthreads and workqueues are fundamentally problematic in
that they effectively introduce a big kernel lock widely used in the
kernel and have already been the culprit of several deadlock
scenarios.  This is the latest occurrence.

During resume, libata rescans all the ports and revalidates all
pre-existing devices.  If it determines that a device has gone
missing, the device is removed from the system which involves
invalidating block device and flushing bdi while holding driver core
layer locks.  Unfortunately, this can race with the rest of device
resume.  Because freezable kthreads and workqueues are thawed after
device resume is complete and block device removal depends on
freezable workqueues and kthreads (e.g. bdi_wq, jbd2) to make
progress, this can lead to deadlock - block device removal can't
proceed because kthreads are frozen and kthreads can't be thawed
because device resume is blocked behind block device removal.

839a8e86 ("writeback: replace custom worker pool implementation
with unbound workqueue") made this particular deadlock scenario more
visible but the underlying problem has always been there - the
original forker task and jbd2 are freezable too.  In fact, this is
highly likely just one of many possible deadlock scenarios given that
freezer behaves as a big kernel lock and we don't have any debug
mechanism around it.

I believe the right thing to do is getting rid of freezable kthreads
and workqueues.  This is something fundamentally broken.  For now,
implement a funny workaround in libata - just avoid doing block device
hot[un]plug while the system is frozen.  Kernel engineering at its
finest.  :(

v2: Add EXPORT_SYMBOL_GPL(pm_freezing) for cases where libata is built
    as a module.

v3: Comment updated and polling interval changed to 10ms as suggested
    by Rafael.

v4: Add #ifdef CONFIG_FREEZER around the hack as pm_freezing is not
    defined when FREEZER is not configured thus breaking build.
    Reported by kbuild test robot.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: NTomaž Šolc <tomaz.solc@tablix.org>
Reviewed-by: N"Rafael J. Wysocki" <rjw@rjwysocki.net>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=62801
Link: http://lkml.kernel.org/r/20131213174932.GA27070@htj.dyndns.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: stable@vger.kernel.org
Cc: kbuild test robot <fengguang.wu@intel.com>