Move G33 and Pineview higher up in the list. Add a couple of blank lines
for OCD while at it.
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/ef4cc8e6ddf592c8c2769b84d4b88a5422d46ea5.1480520526.git.jani.nikula@intel.com

The platform flags in device info are (mostly) mutually
exclusive. Replace the flags with an enum. Add the platform enum also
for platforms that previously didn't have a flag, and give them codename
logging in dmesg.

Pineview remains an exception, the platform being G33 for that.

v2: Sort enum by gen and date

v3: rebase on geminilake enabling
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480596595-3278-1-git-send-email-jani.nikula@intel.com

The firmware interface file was initially partially autogenerated, but
this is no longer the case.

It was never updated automatically, and a lot manual changes were
introduced since.

>From now on any changes to the firmware interface will be managed by
hand, which gives us flexibility when it comes to structure reuse
(HuC/GuC) and naming conventions.

Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: Jeff Mcgee <jeff.mcgee@intel.com>
Cc: Sagar A. Kamble <sagar.a.kamble@intel.com>
Signed-off-by: NArkadiusz Hiler <arkadiusz.hiler@intel.com>
Reviewed-by: NJeff McGee <jeff.mcgee@intel.com>
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480953869-25267-1-git-send-email-arkadiusz.hiler@intel.com

As it already says in the comment block...
Signed-off-by: NMichel Thierry <michel.thierry@intel.com>
Reviewed-by: NMichał Winiarski <michal.winiarski@intel.com>
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161206015704.12654-1-michel.thierry@intel.com

Instead of being hidden in sanitize_enable_ppgtt.
It also seems to be the place to do so nowadays.
Signed-off-by: NMichel Thierry <michel.thierry@intel.com>
Reviewed-by: NMichał Winiarski <michal.winiarski@intel.com>
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>

On all platforms we now always read the contents of buffers via the GTT,
i.e. using WC cpu access. Reads are slow, but they can be accelerated
with an internal read buffer using sse4.1 (movntqda). This is our
i915_memcpy_from_wc() routine which also checks for sse4.1 support and
so we can fallback to using a regular slow memcpy if we need to.

When compressing the pages, the reads are currently done inside zlib's
fill_window() routine and so we must copy the page into a temporary
which is then already inside the CPU cache and fast for zlib's
compression. When not compressing the pages, we don't need a temporary
and can just use the accelerated read from WC into the destination.

v2: Use zstream locals to reduce diff and allocate the additional
temporary storage only if sse4.1 is supported.
v3: Use length=0 for the sse4.1 support check
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161206124051.17040-1-chris@chris-wilson.co.ukReviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>

Use BUILD_BUG_ON_INVALID(expr) in GEM_BUG_ON when building without
DEBUG_GEM. This means the compiler can now check the validity of expr
without generating any code, in turn preventing us from inadvertently
breaking the build when DEBUG_GEM is not enabled.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161202184750.3843-1-matthew.auld@intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

list.h provides a macro for updating the next element in a safe
list-iter, so let's use it so that it is hopefully clearer to the reader
about the unusual behaviour, and also easier to grep.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161205142941.21965-6-chris@chris-wilson.co.uk

Only once the debugobject symbols are exported can we enable support for
debugging swfences when i915 is built as a module. Requires commit
2617fdca3f68 ("lib/debugobjects: export for use in modules")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161205142941.21965-5-chris@chris-wilson.co.uk

As we use debugobjects to track the lifetime of fences within our atomic
state, we ideally want to mark those objects as freed along with their
containers. This merits us hookin into config->funcs->atomic_state_free
for this purpose.

This allows us to enable debugobjects for sw-fences without triggering
known issues.

Fixes: fc158405 ("drm/i915: Integrate i915_sw_fence with debugobjects")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161205142941.21965-4-chris@chris-wilson.co.uk

We can replace a couple of tests with an assertion that the passed in
node is already allocated (as matches the existing call convention) and
by a small bit of refactoring we can bring the line lengths to under
80cols.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161205142941.21965-3-chris@chris-wilson.co.uk

Soft-pinning depends upon being able to check for availabilty of an
interval and evict overlapping object from a drm_mm range manager very
quickly. Currently it uses a linear list, and so performance is dire and
not suitable as a general replacement. Worse, the current code will oops
if it tries to evict an active buffer.

It also helps if the routine reports the correct error codes as expected
by its callers and emits a tracepoint upon use.

For posterity since the wrong patch was pushed (i.e. that missed these
key points and had known bugs), this is the changelog that should have
been on commit 506a8e87 ("drm/i915: Add soft-pinning API for
execbuffer"):

Userspace can pass in an offset that it presumes the object is located
at. The kernel will then do its utmost to fit the object into that
location. The assumption is that userspace is handling its own object
locations (for example along with full-ppgtt) and that the kernel will
rarely have to make space for the user's requests.

This extends the DRM_IOCTL_I915_GEM_EXECBUFFER2 to do the following:
* if the user supplies a virtual address via the execobject->offset
  *and* sets the EXEC_OBJECT_PINNED flag in execobject->flags, then
  that object is placed at that offset in the address space selected
  by the context specifier in execbuffer.
* the location must be aligned to the GTT page size, 4096 bytes
* as the object is placed exactly as specified, it may be used by this
  execbuffer call without relocations pointing to it

It may fail to do so if:
* EINVAL is returned if the object does not have a 4096 byte aligned
  address
* the object conflicts with another pinned object (either pinned by
  hardware in that address space, e.g. scanouts in the aliasing ppgtt)
  or within the same batch.
  EBUSY is returned if the location is pinned by hardware
  EINVAL is returned if the location is already in use by the batch
* EINVAL is returned if the object conflicts with its own alignment (as meets
  the hardware requirements) or if the placement of the object does not fit
  within the address space

All other execbuffer errors apply.

Presence of this execbuf extension may be queried by passing
I915_PARAM_HAS_EXEC_SOFTPIN to DRM_IOCTL_I915_GETPARAM and checking for
a reported value of 1 (or greater).

v2: Combine the hole/adjusted-hole ENOSPC checks
v3: More color, more splitting, more blurb.

Fixes: 506a8e87 ("drm/i915: Add soft-pinning API for execbuffer")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161205142941.21965-2-chris@chris-wilson.co.uk

We need to distinguish between full i915_vma structs and simple
drm_mm_nodes when considering eviction (i.e. we must be careful not to
treat a mere drm_mm_node as a much larger i915_vma causing memory
corruption, if we are lucky). To do this, color these not-a-vma with -1
(I915_COLOR_UNEVICTABLE).

v2...v200: New name for -1.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161205142941.21965-1-chris@chris-wilson.co.uk

On my Cherrytrail CUBE iwork8 Air tablet PIPE-A would get stuck on loading
i915 at boot 1 out of every 3 boots, resulting in a non functional LCD.
Once the i915 driver has successfully loaded, the panel can be disabled /
enabled without hitting this issue.

The getting stuck is caused by vlv_init_display_clock_gating() clearing
the DPOUNIT_CLOCK_GATE_DISABLE bit in DSPCLK_GATE_D when called from
chv_pipe_power_well_ops.enable() on driver load, while a pipe is enabled
driving the DSI LCD by the BIOS.

Clearing this bit while DSI is in use is a known issue and
intel_dsi_pre_enable() / intel_dsi_post_disable() already set / clear it
as appropriate.

This commit modifies vlv_init_display_clock_gating() to leave the
DPOUNIT_CLOCK_GATE_DISABLE bit alone fixing the pipe getting stuck.

Changes in v2:
-Replace PIPE-A with "a pipe" or "the pipe" in the commit msg and
comment

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97330
Cc: stable@vger.kernel.org
Signed-off-by: NHans de Goede <hdegoede@redhat.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161202142904.25613-1-hdegoede@redhat.comSigned-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>

Rather than accessing crtc->config in vlv_compute_wm_level() let's
pass in the crtc state explicitly. One step closer to atomic.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-16-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Add small helpers to make the intent of the staggered enable/disable
sequence in vlv_program_watermarks() easier on the eyes.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-15-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

We'll want to decouple the vlv/chv wm register reprogramming from any
single pipe. So let's just write all the DDL registers in one go. We
already write all the wm registers anyway since the bits are sprinkled
all over the place and so writing them for just a single pipe would have
been too messy anyway.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-14-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

On VLV/CHV some of the watermark values are split across two registers:
low order bits in one, and high order bits in another. So we may not be
able to update a single watermark value atomically, and thus we must be
careful that we don't temporarily introduce out of bounds values during
the reprogramming. To prevent this we can simply zero out all the high
order bits initially, then we update the low order bits, and finally
we update the high order bits with the final value.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-13-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Before we attempt to turn any planes on or off we must first exit
csxr. That's due to cxsr effectively making the plane enable bits
read-only. Currently we achieve that with a vblank wait right after
toggling the cxsr enable bit. We do the vblank wait even if cxsr was
already off, which seems wasteful, so let's try to only do it when
absolutely necessary.

We could start tracking the cxsr state fully somewhere, but for now
it seems easiest to just have intel_set_memory_cxsr() return the
previous cxsr state.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-11-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Let's protect the cxsr state with the wm_mutex, since it might
get poked from multiple places if there's a parallel plane update
happening with a pipe getting enable/disabled.

It's still pretty racy for the old platforms, but for vlv/chv it
should work, I think. If not, we'll improve it later anyway.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-10-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Passing dev_priv instead of dev is the future. Let's make the vlv/chv wm
functions respect that idea.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-9-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Add a small helper to do invert the vlv/chv values. Less fragile
perhaps, and let's us clearly mark all overlarge wateramarks as
disabled (by just making them all USHRT_MAX).
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-8-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Store the vlv/chv watermark values in straight up arrays indexed by
enum plane_id. Avoids a lot of useless checks for the plane type when
we don't have to think which structure member we need to access.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-7-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

The code for vlv and chv wm latency/function pointer setup is
identical. Drop one of the copies.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-6-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Let's compute the maxfifo watermarks using max() instead of min().
Can't even recall why I did it the other way originally. Anyways
using max() avoids having to initialize the watermarks to the max
value first.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-5-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

The watermark should never exceed the FIFO size, so we need to
check against the current FIFO size instead of the theoretical
maximum when we clamp the level 0 watermark.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-4-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

ilk_disable_lp_wm() will tell us whether the LP1+ watermarks were
disabled or not, and hence whether we need to for the vblank wait or
not. Let's use that information to eliminate some useless vblank
waits.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-3-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

HSW+ all use the .initial_watermarks() hook, so there's no point in
calling intel_update_watermarks() from HSW+ specific code. We'll still
hang on to the .initial_watermarks NULL check since theoretically if the
memory latencies are not populated we would not populate the function
pointer either.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480354637-14209-2-git-send-email-ville.syrjala@linux.intel.comReviewed-by: NMaarten Lankhorst <maarten.lankhorst@linux.intel.com>

Not validating the mode rate against max. link rate results in not pruning
invalid modes. For e.g, a HBR2 5.4 Gbps 2-lane configuration does not
support 4k@60Hz. But, we do not reject this mode.

So, make use of the helpers in intel_dp to validate mode data rate against
max. link data rate of a configuration.

v3: Renamed local variables again for consistency (Manasi)
v2: Renamed mode data rate local variable to be more explanatory.
Signed-off-by: NDhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1479243546-17189-1-git-send-email-dhinakaran.pandiyan@intel.comSigned-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>

We store DP link rates as link clock frequencies in kHz, just like all
other clock values. But, DP link rates in the DP Spec. are expressed in
Gbps/lane, which seems to have led to some confusion.

E.g., for HBR2
Max. data rate = 5.4 Gbps/lane x 4 lane x 8/10 x 1/8 = 2160000 kBps
where, 8/10 is for channel encoding and 1/8 is for bit to Byte conversion

Using link clock frequency, like we do
Max. data rate = 540000 kHz * 4 lanes = 2160000 kSymbols/s
Because, each symbol has 8 bit of data, this is 2160000 kBps
and there is no need to account for channel encoding here.

But, currently we do 540000 kHz * 4 lanes * (8/10) = 1728000 kBps

Similarly, while computing the required link bandwidth for a mode,
there is a mysterious 1/10 term.
This should simply be pixel_clock kHz * (bpp/8) to give the final result in
kBps

v2: Changed to DIV_ROUND_UP() and comment changes (Ville)
Signed-off-by: NDhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1479160220-17794-1-git-send-email-dhinakaran.pandiyan@intel.comSigned-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>

These char devices exposing the driver's I2C and DP-AUX adapters for
user space tools are useful to debug display output related issues.
Enable them with the rest of additional driver debug options.
Suggested-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480696541-13697-1-git-send-email-imre.deak@intel.com

Resync, and we need all the fancy new drm_mm stuff to implement more
efficient evict algorithms for softpin.
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

Linux 4.9-rc8

Daniel requested this so we could apply some follow on fixes cleanly to -next.

Pull drm fixes from Dave Airlie:
 "A pretty small pull request: a couple of AMD powerxpress regression
  fixes and a power management fix, a couple of i915 fixes and one hdlcd
  fix, along with one core don't oops because of incorrect API usage fix"

* tag 'drm-fixes-for-v4.9-rc8' of git://people.freedesktop.org/~airlied/linux:
  drm/i915: drop the struct_mutex when wedged or trying to reset
  drm/i915: Don't touch NULL sg on i915_gem_object_get_pages_gtt() error
  drm: Don't call drm_for_each_crtc with a non-KMS driver
  drm/radeon: fix check for port PM availability
  drm/amdgpu: fix check for port PM availability
  drm/amd/powerplay: initialize the soft_regs offset in struct smu7_hwmgr
  drm: hdlcd: Fix cleanup order

Merge tag 'drm-intel-fixes-2016-12-01' of git://anongit.freedesktop.org/git/drm-intel into drm-fixes

2 intel fixes.

* tag 'drm-intel-fixes-2016-12-01' of git://anongit.freedesktop.org/git/drm-intel:
  drm/i915: drop the struct_mutex when wedged or trying to reset
  drm/i915: Don't touch NULL sg on i915_gem_object_get_pages_gtt() error

Merge more fixes from Andrew Morton:
 "2 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm, vmscan: add cond_resched() into shrink_node_memcg()
  mm: workingset: fix NULL ptr in count_shadow_nodes

Boris Zhmurov has reported RCU stalls during the kswapd reclaim:

  INFO: rcu_sched detected stalls on CPUs/tasks:
   23-...: (22 ticks this GP) idle=92f/140000000000000/0 softirq=2638404/2638404 fqs=23
   (detected by 4, t=6389 jiffies, g=786259, c=786258, q=42115)
  Task dump for CPU 23:
  kswapd1         R  running task        0   148      2 0x00000008
  Call Trace:
    shrink_node+0xd2/0x2f0
    kswapd+0x2cb/0x6a0
    mem_cgroup_shrink_node+0x160/0x160
    kthread+0xbd/0xe0
    __switch_to+0x1fa/0x5c0
    ret_from_fork+0x1f/0x40
    kthread_create_on_node+0x180/0x180

a closer code inspection has shown that we might indeed miss all the
scheduling points in the reclaim path if no pages can be isolated from
the LRU list.  This is a pathological case but other reports from Donald
Buczek have shown that we might indeed hit such a path:

        clusterd-989   [009] .... 118023.654491: mm_vmscan_direct_reclaim_end: nr_reclaimed=193
         kswapd1-86    [001] dN.. 118023.987475: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239830 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118024.320968: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239844 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118024.654375: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239858 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118024.987036: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239872 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118025.319651: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239886 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118025.652248: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239900 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118025.984870: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239914 nr_taken=0 file=1
  [...]
         kswapd1-86    [001] dN.. 118084.274403: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4241133 nr_taken=0 file=1

this is minute long snapshot which didn't take a single page from the
LRU.  It is not entirely clear why only 1303 pages have been scanned
during that time (maybe there was a heavy IRQ activity interfering).

In any case it looks like we can really hit long periods without
scheduling on non preemptive kernels so an explicit cond_resched() in
shrink_node_memcg which is independent on the reclaim operation is due.

Link: http://lkml.kernel.org/r/20161202095841.16648-1-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Reported-by: NBoris Zhmurov <bb@kernelpanic.ru>
Tested-by: NBoris Zhmurov <bb@kernelpanic.ru>
Reported-by: NDonald Buczek <buczek@molgen.mpg.de>
Reported-by: N"Christopher S. Aker" <caker@theshore.net>
Reported-by: NPaul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit 0a6b76dd ("mm: workingset: make shadow node shrinker memcg
aware") has made the workingset shadow nodes shrinker memcg aware.  The
implementation is not correct though because memcg_kmem_enabled() might
become true while we are doing a global reclaim when the sc->memcg might
be NULL which is exactly what Marek has seen:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000400
  IP: [<ffffffff8122d520>] mem_cgroup_node_nr_lru_pages+0x20/0x40
  PGD 0
  Oops: 0000 [#1] SMP
  CPU: 0 PID: 60 Comm: kswapd0 Tainted: G           O   4.8.10-12.pvops.qubes.x86_64 #1
  task: ffff880011863b00 task.stack: ffff880011868000
  RIP: mem_cgroup_node_nr_lru_pages+0x20/0x40
  RSP: e02b:ffff88001186bc70  EFLAGS: 00010293
  RAX: 0000000000000000 RBX: ffff88001186bd20 RCX: 0000000000000002
  RDX: 000000000000000c RSI: 0000000000000000 RDI: 0000000000000000
  RBP: ffff88001186bc70 R08: 28f5c28f5c28f5c3 R09: 0000000000000000
  R10: 0000000000006c34 R11: 0000000000000333 R12: 00000000000001f6
  R13: ffffffff81c6f6a0 R14: 0000000000000000 R15: 0000000000000000
  FS:  0000000000000000(0000) GS:ffff880013c00000(0000) knlGS:ffff880013d00000
  CS:  e033 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000000400 CR3: 00000000122f2000 CR4: 0000000000042660
  Call Trace:
    count_shadow_nodes+0x9a/0xa0
    shrink_slab.part.42+0x119/0x3e0
    shrink_node+0x22c/0x320
    kswapd+0x32c/0x700
    kthread+0xd8/0xf0
    ret_from_fork+0x1f/0x40
  Code: 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 3b 35 dd eb b1 00 55 48 89 e5 73 2c 89 d2 31 c9 31 c0 4c 63 ce 48 0f a3 ca 73 13 <4a> 8b b4 cf 00 04 00 00 41 89 c8 4a 03 84 c6 80 00 00 00 83 c1
  RIP  mem_cgroup_node_nr_lru_pages+0x20/0x40
   RSP <ffff88001186bc70>
  CR2: 0000000000000400
  ---[ end trace 100494b9edbdfc4d ]---

This patch fixes the issue by checking sc->memcg rather than
memcg_kmem_enabled() which is sufficient because shrink_slab makes sure
that only memcg aware shrinkers will get non-NULL memcgs and only if
memcg_kmem_enabled is true.

Fixes: 0a6b76dd ("mm: workingset: make shadow node shrinker memcg aware")
Link: http://lkml.kernel.org/r/20161201132156.21450-1-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Reported-by: NMarek Marczykowski-Górecki <marmarek@mimuw.edu.pl>
Tested-by: NMarek Marczykowski-Górecki <marmarek@mimuw.edu.pl>
Acked-by: NVladimir Davydov <vdavydov.dev@gmail.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NBalbir Singh <bsingharora@gmail.com>
Cc: <stable@vger.kernel.org>	[4.6+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>