This code is ancient, and goes back to when we only had a single page
for the pipe buffers.  The exact history is hidden in the mists of time
(ie "before git", and in fact predates the BK repository too).

At that long-ago point in time, it actually helped to try to merge big
back-and-forth pipe reads and writes, and not limit pipe reads to the
single pipe buffer in length just because that was all we had at a time.

However, since then we've expanded the pipe buffers to multiple pages,
and this logic really doesn't seem to make sense.  And a lot of it is
somewhat questionable (ie "hmm, the user asked for a non-blocking read,
but we see that there's a writer pending, so let's wait anyway to get
the extra data that the writer will have").

But more importantly, it makes the "go to sleep" logic much less
obvious, and considering the wakeup issues we've had, I want to make for
less of those kinds of things.

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This is the read side version of the previous commit: it simplifies the
logic to only wake up waiting writers when necessary, and makes sure to
use a synchronous wakeup.  This time not so much for GNU make jobserver
reasons (that pipe never fills up), but simply to get the writer going
quickly again.

A bit less verbose commentary this time, if only because I assume that
the write side commentary isn't going to be ignored if you touch this
code.

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The pipe rework ends up having been extra painful, partly becaused of
actual bugs with ordering and caching of the pipe state, but also
because of subtle performance issues.

In particular, the pipe rework caused the kernel build to inexplicably
slow down.

The reason turns out to be that the GNU make jobserver (which limits the
parallelism of the build) uses a pipe to implement a "token" system: a
parallel submake will read a character from the pipe to get the job
token before starting a new job, and will write a character back to the
pipe when it is done.  The overall job limit is thus easily controlled
by just writing the appropriate number of initial token characters into
the pipe.

But to work well, that really means that the old behavior of write
wakeups being synchronous (WF_SYNC) is very important - when the pipe
writer wakes up a reader, we want the reader to actually get scheduled
immediately.  Otherwise you lose the parallelism of the build.

The pipe rework lost that synchronous wakeup on write, and we had
clearly all forgotten the reasons and rules for it.

This rewrites the pipe write wakeup logic to do the required Wsync
wakeups, but also clarifies the logic and avoids extraneous wakeups.

It also ends up addign a number of comments about what oit does and why,
so that we hopefully don't end up forgetting about this next time we
change this code.

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The kernel wait queues have a basic rule to them: you add yourself to
the wait-queue first, and then you check the things that you're going to
wait on.  That avoids the races with the event you're waiting for.

The same goes for poll/select logic: the "poll_wait()" goes first, and
then you check the things you're polling for.

Of course, if you use locking, the ordering doesn't matter since the
lock will serialize with anything that changes the state you're looking
at. That's not the case here, though.

So move the poll_wait() first in pipe_poll(), before you start looking
at the pipe state.

Fixes: 8cefc107 ("pipe: Use head and tail pointers for the ring, not cursor and length")
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull ARM fixes from Russell King:

 - fix CPU topology setup for SCHED_MC case

 - fix VDSO regression

* tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm:
  ARM: 8947/1: Fix __arch_get_hw_counter() access to CNTVCT
  ARM: 8943/1: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC

Pull ARM SoC fixes from Olof Johansson:
 "A set of fixes that we've merged late, but for the most part that have
  been sitting in -next for a while through platform maintainer trees:

   - Fixes to suspend/resume on Tegra, caused by the added features this
     merge window

   - Cleanups and minor fixes to TI additions this merge window

   - Tee fixes queued up late before the merge window, included here.

   - A handful of other fixlets

  There's also a refresh of the shareed config files (multi_v* on
  32-bit, and defconfig on 64-bit), to avoid conflicts when we get new
  contributions"

* tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc: (32 commits)
  ARM: multi_v7_defconfig: Restore debugfs support
  ARM: defconfig: re-run savedefconfig on multi_v* configs
  arm64: defconfig: re-run savedefconfig
  ARM: pxa: Fix resource properties
  soc: mediatek: cmdq: fixup wrong input order of write api
  soc: aspeed: Fix snoop_file_poll()'s return type
  MAINTAINERS: Switch to Marvell addresses
  MAINTAINERS: update Cavium ThunderX drivers
  Revert "arm64: dts: juno: add dma-ranges property"
  MAINTAINERS: Make Nicolas Saenz Julienne the new bcm2835 maintainer
  firmware: arm_scmi: Avoid double free in error flow
  arm64: dts: juno: Fix UART frequency
  ARM: dts: Fix sgx sysconfig register for omap4
  arm: socfpga: execute cold reboot by default
  ARM: dts: Fix vcsi regulator to be always-on for droid4 to prevent hangs
  ARM: dts: dra7: fix cpsw mdio fck clock
  ARM: dts: am57xx-beagle-x15: Update pinmux name to ddr_3_3v
  ARM: dts: omap3-tao3530: Fix incorrect MMC card detection GPIO polarity
  soc/tegra: pmc: Add reset sources and levels on Tegra194
  soc/tegra: pmc: Add missing IRQ callbacks on Tegra194
  ...

Pull arm64 fixes from Catalin Marinas:

 - ZONE_DMA32 initialisation fix when memblocks fall entirely within the
   first GB (used by ZONE_DMA in 5.5 for Raspberry Pi 4).

 - Couple of ftrace fixes following the FTRACE_WITH_REGS patchset.

 - access_ok() fix for the Tagged Address ABI when called from from a
   kernel thread (asynchronous I/O): the kthread does not have the TIF
   flags of the mm owner, so untag the user address unconditionally.

 - KVM compute_layout() called before the alternatives code patching.

 - Minor clean-ups.

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: entry: refine comment of stack overflow check
  arm64: ftrace: fix ifdeffery
  arm64: KVM: Invoke compute_layout() before alternatives are applied
  arm64: Validate tagged addresses in access_ok() called from kernel threads
  arm64: mm: Fix column alignment for UXN in kernel_page_tables
  arm64: insn: consistently handle exit text
  arm64: mm: Fix initialisation of DMA zones on non-NUMA systems

Fix the iteration end check in fuse_dev_splice_write().  The iterator
position can only be compared with == or != since wrappage may be involved.

Fixes: 8cefc107 ("pipe: Use head and tail pointers for the ring, not cursor and length")
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull more powerpc updates from Michael Ellerman:
 "A few commits splitting the KASAN instrumented bitops header in three,
  to match the split of the asm-generic bitops headers.

  This is needed on powerpc because we use the generic bitops for the
  non-atomic case only, whereas the existing KASAN instrumented bitops
  assume all the underlying operations are provided by the arch as
  arch_foo() versions.

  Thanks to: Daniel Axtens & Christophe Leroy"

* tag 'powerpc-5.5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  docs/core-api: Remove possibly confusing sub-headings from Bit Operations
  powerpc: support KASAN instrumentation of bitops
  kasan: support instrumented bitops combined with generic bitops

Pull powerpc fixes from Michael Ellerman:
 "One fix for a regression introduced by our recent rework of cache
  flushing on memory hotunplug.

  Like several other arches, our VDSO clock_getres() needed a fix to
  match the semantics of posix_get_hrtimer_res().

  A fix for a boot crash on Power9 LPARs using PCI LSI interrupts.

  A commit disabling use of the trace_imc PMU (not the core PMU) on
  Power9 systems, because it can lead to checkstops, until a workaround
  is developed.

  A handful of other minor fixes.

  Thanks to: Aneesh Kumar K.V, Anju T Sudhakar, Ard Biesheuvel,
  Christophe Leroy, Cédric Le Goater, Madhavan Srinivasan, Vincenzo
  Frascino"

* tag 'powerpc-5.5-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/perf: Disable trace_imc pmu
  powerpc/powernv: Avoid re-registration of imc debugfs directory
  powerpc/pmem: Convert to EXPORT_SYMBOL_GPL
  powerpc/archrandom: fix arch_get_random_seed_int()
  powerpc: Fix vDSO clock_getres()
  powerpc/pmem: Fix kernel crash due to wrong range value usage in flush_dcache_range
  powerpc/xive: Skip ioremap() of ESB pages for LSI interrupts
  powerpc/kasan: Fix boot failure with RELOCATABLE && FSL_BOOKE

Pull more sound updates from Takashi Iwai:
 "A few last-minute updates, most of them are the regression fixes:

   - AMD HD-audio HDMI runtime PM improvements

   - Fixes for HD-audio HDMI regressions wrt DP-MST

   - A regression fix for the previous aloop enhancement

   - A fix for a long-time problem in PCM OSS layer that was spotted by
     fuzzer now

   - A few HD-audio quirks"

* tag 'sound-fix-5.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound:
  ALSA: pcm: oss: Avoid potential buffer overflows
  ALSA: hda: hdmi - Keep old slot assignment behavior for Intel platforms
  ALSA: hda: Modify stream stripe mask only when needed
  ALSA: hda - fixup for the bass speaker on Lenovo Carbon X1 7th gen
  ALSA: hda: hdmi - preserve non-MST PCM routing for Intel platforms
  ALSA: hda: hdmi - fix kernel oops caused by invalid PCM idx
  ALSA: hda/realtek - Fix inverted bass GPIO pin on Acer 8951G
  ALSA: hda/realtek - Dell headphone has noise on unmute for ALC236
  ALSA: hda: hdmi - fix regression in connect list handling
  ALSA: aloop: Avoid pointer dereference before null-check
  ALSA: hda/hdmi - enable automatic runtime pm for AMD HDMI codecs by default
  ALSA: hda/hdmi - enable runtime pm for newer AMD display audio
  ALSA: hda/hdmi - Add new pci ids for AMD GPU display audio
  ALSA: hda/hdmi - fix vgaswitcheroo detection for AMD

Similarly to commit 8f868d68 ("pipe: Fix missing mask update after
pipe_wait()") this fixes a case where the pipe rewrite ended up caching
the pipe state incorrectly over a pipe lock drop event.

It wasn't quite as obvious, because you needed to splice data from a
pipe to a file, which is a fairly unusual operation, but it's completely
wrong.

Make sure we load the pipe head/tail/size information only after we've
waited for there to be data in the pipe.

While in that file, also make one of the splice helper functions use the
canonical arghument order for pipe_empty().  That's syntactic - pipe
emptiness is just that head and tail are equal, and thus mixing up head
and tail doesn't really matter.  It's still wrong, though.
Reported-by: David Sterba <dsterba@suse.cz>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull more drm updates from Dave Airlie:
 "Rob pointed out I missed his pull request for msm-next, it's been in
  next for a while outside of my tree so shouldn't cause any unexpected
  issues, it has some OCMEM support in drivers/soc that is acked by
  other maintainers as it's outside my tree.

  Otherwise it's a usual fixes pull, i915, amdgpu, the main ones, with
  some tegra, omap, mgag200 and one core fix.

  Summary:

  msm-next:
   - OCMEM support for a3xx and a4xx GPUs.
   - a510 support + display support

  core:
   - mst payload deletion fix

  i915:
   - uapi alignment fix
   - fix for power usage regression due to security fixes
   - change default preemption timeout to 640ms from 100ms
   - EHL voltage level display fixes
   - TGL DGL PHY fix
   - gvt - MI_ATOMIC cmd parser fix, CFL non-priv warning
   - CI spotted deadlock fix
   - EHL port D programming fix

  amdgpu:
   - VRAM lost fixes on BACO for CI/VI
   - navi14 DC fixes
   - misc SR-IOV, gfx10 fixes
   - XGMI fixes for arcturus
   - SRIOV fixes

  amdkfd:
   - KFD on ppc64le enabled
   - page table optimisations

  radeon:
   - fix for r1xx/2xx register checker.

  tegra:
   - displayport regression fixes
   - DMA API regression fixes

  mgag200:
   - fix devices that can't scanout except at 0 addr

  omap:
   - fix dma_addr refcounting"

* tag 'drm-next-2019-12-06' of git://anongit.freedesktop.org/drm/drm: (100 commits)
  drm/dp_mst: Correct the bug in drm_dp_update_payload_part1()
  drm/omap: fix dma_addr refcounting
  drm/tegra: Run hub cleanup on ->remove()
  drm/tegra: sor: Make the +5V HDMI supply optional
  drm/tegra: Silence expected errors on IOMMU attach
  drm/tegra: vic: Export module device table
  drm/tegra: sor: Implement system suspend/resume
  drm/tegra: Use proper IOVA address for cursor image
  drm/tegra: gem: Remove premature import restrictions
  drm/tegra: gem: Properly pin imported buffers
  drm/tegra: hub: Remove bogus connection mutex check
  ia64: agp: Replace empty define with do while
  agp: Add bridge parameter documentation
  agp: remove unused variable num_segments
  agp: move AGPGART_MINOR to include/linux/miscdevice.h
  agp: remove unused variable size in agp_generic_create_gatt_table
  drm/dp_mst: Fix build on systems with STACKTRACE_SUPPORT=n
  drm/radeon: fix r1xx/r2xx register checker for POT textures
  drm/amdgpu: fix GFX10 missing CSIB set(v3)
  drm/amdgpu: should stop GFX ring in hw_fini
  ...

Pull more block and io_uring updates from Jens Axboe:
 "I wasn't expecting this to be so big, and if I was, I would have used
  separate branches for this. Going forward I'll be doing separate
  branches for the current tree, just like for the next kernel version
  tree. In any case, this contains:

   - Series from Christoph that fixes an inherent race condition with
     zoned devices and revalidation.

   - null_blk zone size fix (Damien)

   - Fix for a regression in this merge window that caused busy spins by
     sending empty disk uevents (Eric)

   - Fix for a regression in this merge window for bfq stats (Hou)

   - Fix for io_uring creds allocation failure handling (me)

   - io_uring -ERESTARTSYS send/recvmsg fix (me)

   - Series that fixes the need for applications to retain state across
     async request punts for io_uring. This one is a bit larger than I
     would have hoped, but I think it's important we get this fixed for
     5.5.

   - connect(2) improvement for io_uring, handling EINPROGRESS instead
     of having applications needing to poll for it (me)

   - Have io_uring use a hash for poll requests instead of an rbtree.
     This turned out to work much better in practice, so I think we
     should make the switch now. For some workloads, even with a fair
     amount of cancellations, the insertion sort is just too expensive.
     (me)

   - Various little io_uring fixes (me, Jackie, Pavel, LimingWu)

   - Fix for brd unaligned IO, and a warning for the future (Ming)

   - Fix for a bio integrity data leak (Justin)

   - bvec_iter_advance() improvement (Pavel)

   - Xen blkback page unmap fix (SeongJae)

  The major items in here are all well tested, and on the liburing side
  we continue to add regression and feature test cases. We're up to 50
  topic cases now, each with anywhere from 1 to more than 10 cases in
  each"

* tag 'for-linus-20191205' of git://git.kernel.dk/linux-block: (33 commits)
  block: fix memleak of bio integrity data
  io_uring: fix a typo in a comment
  bfq-iosched: Ensure bio->bi_blkg is valid before using it
  io_uring: hook all linked requests via link_list
  io_uring: fix error handling in io_queue_link_head
  io_uring: use hash table for poll command lookups
  io-wq: clear node->next on list deletion
  io_uring: ensure deferred timeouts copy necessary data
  io_uring: allow IO_SQE_* flags on IORING_OP_TIMEOUT
  null_blk: remove unused variable warning on !CONFIG_BLK_DEV_ZONED
  brd: warn on un-aligned buffer
  brd: remove max_hw_sectors queue limit
  xen/blkback: Avoid unmapping unmapped grant pages
  io_uring: handle connect -EINPROGRESS like -EAGAIN
  block: set the zone size in blk_revalidate_disk_zones atomically
  block: don't handle bio based drivers in blk_revalidate_disk_zones
  block: allocate the zone bitmaps lazily
  block: replace seq_zones_bitmap with conv_zones_bitmap
  block: simplify blkdev_nr_zones
  block: remove the empty line at the end of blk-zoned.c
  ...

Pull vfs d_inode/d_flags memory ordering fixes from Al Viro:
 "Fallout from tree-wide audit for ->d_inode/->d_flags barriers use.
  Basically, the problem is that negative pinned dentries require
  careful treatment - unless ->d_lock is locked or parent is held at
  least shared, another thread can make them positive right under us.

  Most of the uses turned out to be safe - the main surprises as far as
  filesystems are concerned were

   - race in dget_parent() fastpath, that might end up with the caller
     observing the returned dentry _negative_, due to insufficient
     barriers. It is positive in memory, but we could end up seeing the
     wrong value of ->d_inode in CPU cache. Fixed.

   - manual checks that result of lookup_one_len_unlocked() is positive
     (and rejection of negatives). Again, insufficient barriers (we
     might end up with inconsistent observed values of ->d_inode and
     ->d_flags). Fixed by switching to a new primitive that does the
     checks itself and returns ERR_PTR(-ENOENT) instead of a negative
     dentry. That way we get rid of boilerplate converting negatives
     into ERR_PTR(-ENOENT) in the callers and have a single place to
     deal with the barrier-related mess - inside fs/namei.c rather than
     in every caller out there.

  The guts of pathname resolution *do* need to be careful - the race
  found by Ritesh is real, as well as several similar races.
  Fortunately, it turns out that we can take care of that with fairly
  local changes in there.

  The tree-wide audit had not been fun, and I hate the idea of repeating
  it. I think the right approach would be to annotate the places where
  we are _not_ guaranteed ->d_inode/->d_flags stability and have sparse
  catch regressions. But I'm still not sure what would be the least
  invasive way of doing that and it's clearly the next cycle fodder"

* 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fs/namei.c: fix missing barriers when checking positivity
  fix dget_parent() fastpath race
  new helper: lookup_positive_unlocked()
  fs/namei.c: pull positivity check into follow_managed()

This pull request contains the second batch of changes for Broadcom
ARM-based SoCs, please pull the following:

- Nicolas declares a CMA area within the first 1GB of DRAM in order for
  it to be guaranteed to reside there, otherwise ARM64's memory
  initialization will pick up a CMA area within ZONE_DMA32

- Stefan adds the Device Tree node for the built-in Ethernet controller
  (GENET) on the Raspberry Pi 4 model B board

* tag 'arm-soc/for-5.5/devicetree-part2' of https://github.com/Broadcom/stblinux:
  ARM: dts: bcm2711-rpi-4: Enable GENET support
  ARM: dts: bcm2711: force CMA into first GB of memory

Link: https://lore.kernel.org/r/20191118182931.11884-1-f.fainelli@gmail.comSigned-off-by: Olof Johansson <olof@lixom.net>

Merge tag 'tegra-for-5.5-memory-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux into arm/fixes

memory: tegra: Fixes for v5.5-rc1

This contains a fix for a kernel panic that can occur on suspend if EMC
timings are not available in device tree.

* tag 'tegra-for-5.5-memory-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux:
  memory: tegra30-emc: Fix panic on suspend

Link: https://lore.kernel.org/r/20191204130753.3614278-1-thierry.reding@gmail.comSigned-off-by: Olof Johansson <olof@lixom.net>

Merge tag 'tegra-for-5.5-soc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux into arm/fixes

soc/tegra: Fixes for v5.5-rc1

Fixes a regression for wake events on Tegra194 caused by the Tegra210
support that was added in v5.5-rc1 as well as wrong reset sources and
levels on Tegra194.

* tag 'tegra-for-5.5-soc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux:
  soc/tegra: pmc: Add reset sources and levels on Tegra194
  soc/tegra: pmc: Add missing IRQ callbacks on Tegra194
  soc/tegra: pmc: Use lower-case for hexadecimal literals

Link: https://lore.kernel.org/r/20191204130753.3614278-2-thierry.reding@gmail.comSigned-off-by: Olof Johansson <olof@lixom.net>

Merge tag 'tegra-for-5.5-cpufreq' of git://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux into arm/fixes

cpufreq: tegra: Changes for v5.5-rc1

Implements support for suspend/resume on Tegra124.

* tag 'tegra-for-5.5-cpufreq' of git://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux:
  cpufreq: tegra124: Add suspend and resume support

Link: https://lore.kernel.org/r/20191204130753.3614278-3-thierry.reding@gmail.comSigned-off-by: Olof Johansson <olof@lixom.net>

Merge tag 'socfpga_update_for_v5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/dinguyen/linux into arm/fixes

SoCFPGA updates for v5.5
- Issue COLD reboot by default for SoCFPGA platforms

* tag 'socfpga_update_for_v5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/dinguyen/linux:
  arm: socfpga: execute cold reboot by default

Link: https://lore.kernel.org/r/20191122182106.822-1-dinguyen@kernel.orgSigned-off-by: Olof Johansson <olof@lixom.net>

Merge tag 'omap-for-v5.5/dt-fixes-merge-window-signed' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap into arm/fixes

Device tree fixes for omap variants for for v5.5 merge window

This series of changes contains fixes for few SoC and board specific
issues that would be good to have merged for v5.5-rc1:

- Fix incorrect MMC card detection polarity for omap3-tao3530

- Fix wrong am57xx-beagle-x15 pinmux named states for eMMC

- Fix dra7 cpsw mdio clock that causes wrong speed

- Fix vcsi for droid4 so it won't get turned off after init

- Fix rev and sysconfig register offsets for omap4 sgx so it can idle

Then there are also two minor late changes to logicpd-torpedo-baseboard
to configure 1-wire HDQ for battery stats, and remove out of date
workaround comments no longer needed.

* tag 'omap-for-v5.5/dt-fixes-merge-window-signed' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap:
  ARM: dts: Fix sgx sysconfig register for omap4
  ARM: dts: Fix vcsi regulator to be always-on for droid4 to prevent hangs
  ARM: dts: dra7: fix cpsw mdio fck clock
  ARM: dts: am57xx-beagle-x15: Update pinmux name to ddr_3_3v
  ARM: dts: omap3-tao3530: Fix incorrect MMC card detection GPIO polarity
  ARM: dts: logicpd-torpedo: Remove unnecessary notes/comments
  ARM: dts: logicpd-torpedo-baseboard:  Enable HDQ

Link: https://lore.kernel.org/r/pull-1574870758-237468@atomide.comSigned-off-by: Olof Johansson <olof@lixom.net>

Merge tag 'omap-for-v5.5/ti-sysc-late-signed' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap into arm/fixes

Few ti-sysc related fixes for v5.5 merge window

Just few minor changes that can be merged when suitable, but would
be good to have these in v5.5-rc1 to remove dependencies between branches
for more changes later on in v5.6:

- Add quirk handling for AESS (Audio Engine Sub System)

- We want to drop the useless gptimer option for omap4 as there are local
  timers

- A minor error path handling improvment for sysc_child_add_named_clock()
  that will make further patching a bit easier

* tag 'omap-for-v5.5/ti-sysc-late-signed' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap:
  bus: ti-sysc: Adjust exception handling in sysc_child_add_named_clock()
  ARM: OMAP2+: Drop useless gptimer option for omap4
  bus: ti-sysc: Add module enable quirk for audio AESS

Link: https://lore.kernel.org/r/pull-1574273726-31367@atomide.comSigned-off-by: Olof Johansson <olof@lixom.net>

Commit fd7d58f0 ("ARM: multi_v7_defconfig: renormalize based on recent
additions") removed explicit enable line for CONFIG_DEBUG_FS, because
that feature has been selected by other enabled options: CONFIG_TRACING,
which were enabled by CONFIG_PERF_EVENTS.

In meantime, commit 0e4a459f ("tracing: Remove unnecessary DEBUG_FS
dependency") removed the dependency between CONFIG_DEBUG_FS and
CONFIG_TRACING, so CONFIG_DEBUG_FS is no longer enabled in default builds.

Enable it again explicitly, as debugfs support is essential for various
automated testing tools.

Link: https://lore.kernel.org/r/20191206125112.11006-1-m.szyprowski@samsung.comSigned-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

Stack overflow checking can be done by testing sp & (1 << THREAD_SHIFT)
only for the stacks are aligned to (2 << THREAD_SHIFT) with size of
(1 << THREAD_SIZE), and this is the case when CONFIG_VMAP_STACK is set.

Fix the code comment to avoid confusion.

Cc: Will Deacon <will@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Heyi Guo <guoheyi@huawei.com>
[catalin.marinas@arm.com: Updated comment following Mark's suggestion]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

When I tweaked the ftrace entry assembly in commit:

  3b23e499 ("arm64: implement ftrace with regs")

... my ifdeffery tweaks left ftrace_graph_caller undefined for
CONFIG_DYNAMIC_FTRACE && CONFIG_FUNCTION_GRAPH_TRACER when ftrace is
based on mcount.

The kbuild test robot reported that this issue is detected at link time:

| arch/arm64/kernel/entry-ftrace.o: In function `skip_ftrace_call':
| arch/arm64/kernel/entry-ftrace.S:238: undefined reference to `ftrace_graph_caller'
| arch/arm64/kernel/entry-ftrace.S:238:(.text+0x3c): relocation truncated to fit: R_AARCH64_CONDBR19 against undefined symbol
| `ftrace_graph_caller'
| arch/arm64/kernel/entry-ftrace.S:243: undefined reference to `ftrace_graph_caller'
| arch/arm64/kernel/entry-ftrace.S:243:(.text+0x54): relocation truncated to fit: R_AARCH64_CONDBR19 against undefined symbol
| `ftrace_graph_caller'

This patch fixes the ifdeffery so that the mcount version of
ftrace_graph_caller doesn't depend on CONFIG_DYNAMIC_FTRACE. At the same
time, a redundant #else is removed from the ifdeffery for the
patchable-function-entry version of ftrace_graph_caller.

Fixes: 3b23e499 ("arm64: implement ftrace with regs")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Torsten Duwe <duwe@lst.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

compute_layout() is invoked as part of an alternative fixup under
stop_machine(). This function invokes get_random_long() which acquires a
sleeping lock on -RT which can not be acquired in this context.

Rename compute_layout() to kvm_compute_layout() and invoke it before
stop_machine() applies the alternatives. Add a __init prefix to
kvm_compute_layout() because the caller has it, too (and so the code can be
discarded after boot).
Reviewed-by: James Morse <james.morse@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

__range_ok(), invoked from access_ok(), clears the tag of the user
address only if CONFIG_ARM64_TAGGED_ADDR_ABI is enabled and the thread
opted in to the relaxed ABI. The latter sets the TIF_TAGGED_ADDR thread
flag. In the case of asynchronous I/O (e.g. io_submit()), the
access_ok() may be called from a kernel thread. Since kernel threads
don't have TIF_TAGGED_ADDR set, access_ok() will fail for valid tagged
user addresses. Example from the ffs_user_copy_worker() thread:

	use_mm(io_data->mm);
	ret = ffs_copy_to_iter(io_data->buf, ret, &io_data->data);
	unuse_mm(io_data->mm);

Relax the __range_ok() check to always untag the user address if called
in the context of a kernel thread. The user pointers would have already
been checked via aio_setup_rw() -> import_{single_range,iovec}() at the
time of the asynchronous I/O request.

Fixes: 63f0c603 ("arm64: Introduce prctl() options to control the tagged user addresses ABI")
Cc: <stable@vger.kernel.org> # 5.4.x-
Cc: Will Deacon <will@kernel.org>
Reported-by: Evgenii Stepanov <eugenis@google.com>
Tested-by: Evgenii Stepanov <eugenis@google.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

__arch_get_hw_counter() should check clock_mode to see if it can access
CNTVCT. With the conversion to unified vDSO this check has been left out.

This causes on imx v6 and v7 (imx_v6_v7_defconfig) and other platforms to
hang at boot during the execution of the init process as per below:

[   19.976852] Run /sbin/init as init process
[   20.044931] Kernel panic - not syncing: Attempted to kill init!
exitcode=0x00000004

Fix the problem verifying that clock_mode is set coherently before
accessing CNTVCT.
Investigated-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

Commit ca74b316 ("arm: Use common cpu_topology structure and
functions.") changed cpu_coregroup_mask() from the ARM32 specific
implementation in arch/arm/include/asm/topology.h to the one shared
with ARM64 and RISCV in drivers/base/arch_topology.c.

Currently on ARM32 (TC2 w/ CONFIG_SCHED_MC) the task scheduler setup
code (w/ CONFIG_SCHED_DEBUG) shows this during CPU hotplug:

  ERROR: groups don't span domain->span

It happens to CPUs of the cluster of the CPU which gets hot-plugged
out on scheduler domain MC.

Turns out that the shared cpu_coregroup_mask() requires that the
hot-plugged CPU is removed from the core_sibling mask via
remove_cpu_topology(). Otherwise the 'is core_sibling subset of
cpumask_of_node()' doesn't work. In this case the task scheduler has to
deal with cpumask_of_node instead of core_sibling which is wrong on
scheduler domain MC.

e.g. CPU3 hot-plugged out on TC2 [cluster0: 0,3-4 cluster1: 1-2]:

  cpu_coregroup_mask(): CPU3 cpumask_of_node=0-2,4 core_sibling=0,3-4
                                                                  ^
should be:

  cpu_coregroup_mask(): CPU3 cpumask_of_node=0-2,4 core_sibling=0,4

Add remove_cpu_topology() to __cpu_disable() to remove the CPU from the
topology masks in case of a CPU hotplug out operation.

At the same time tweak store_cpu_topology() slightly so it will call
update_siblings_masks() in case of CPU hotplug in operation via
secondary_start_kernel()->smp_store_cpu_info().

This aligns the ARM32 implementation with the ARM64 one.

Guarding remove_cpu_topology() with CONFIG_GENERIC_ARCH_TOPOLOGY is
necessary since some Arm32 defconfigs (aspeed_g5_defconfig,
milbeaut_m10v_defconfig, spear13xx_defconfig) specify an explicit

 # CONFIG_ARM_CPU_TOPOLOGY is not set

w/ ./arch/arm/Kconfig: select GENERIC_ARCH_TOPOLOGY if ARM_CPU_TOPOLOGY

Fixes: ca74b316 ("arm: Use common cpu_topology structure and functions")
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Tested-by: Ondrej Jirman <megous@megous.com>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

Merge tag 'drm-intel-next-fixes-2019-12-05' of git://anongit.freedesktop.org/drm/drm-intel into drm-next

- Includes gvt-next-fixes-2019-12-02 pull
- Fixes for CI spotted eadlock and a race condition in GEM contexts
- Fix for EHL port D programming
Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191205092412.GA8089@jlahtine-desk.ger.corp.intel.com

* io_uring-5.5:
  io_uring: fix a typo in a comment
  io_uring: hook all linked requests via link_list
  io_uring: fix error handling in io_queue_link_head
  io_uring: use hash table for poll command lookups

Pull autofs updates from Al Viro:
 "autofs misuses checks for ->d_subdirs emptiness; the cursors are in
  the same lists, resulting in false negatives. It's not needed anyway,
  since autofs maintains counter in struct autofs_info, containing 0 for
  removed ones, 1 for live symlinks and 1 + number of children for live
  directories, which is precisely what we need for those checks.

  This series switches to use of that counter and untangles the crap
  around its uses (it needs not be atomic and there's a bunch of
  completely pointless "defensive" checks).

  This fell out of dcache_readdir work; the main point is to get rid of
  ->d_subdirs abuses in there. I've more followup cleanups, but I hadn't
  run those by Ian yet, so they can go next cycle"

* 'next.autofs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  autofs: don't bother with atomics for ino->count
  autofs_dir_rmdir(): check ino->count for deciding whether it's empty...
  autofs: get rid of pointless checks around ->count handling
  autofs_clear_leaf_automount_flags(): use ino->count instead of ->d_subdirs

Merge two fixes for the pipe rework from David Howells:
 "Here are a couple of patches to fix bugs syzbot found in the pipe
  changes:

   - An assertion check will sometimes trip when polling a pipe because
     the ring size and indices used are approximate and may be being
     changed simultaneously.

     An equivalent approximate calculation was done previously, but
     without the assertion check, so I've just dropped the check. To
     make it accurate, the pipe mutex would need to be taken or the spin
     lock could be used - but usage of the spinlock would need to be
     rolled out into splice, iov_iter and other places for that.

   - The index mask and the max_usage values cannot be cached across
     pipe_wait() as F_SETPIPE_SZ could have been called during the wait.
     This can cause pipe_write() to break"

* pipe-rework:
  pipe: Fix missing mask update after pipe_wait()
  pipe: Remove assertion from pipe_poll()

Fix pipe_write() to not cache the ring index mask and max_usage as their
values are invalidated by calling pipe_wait() because the latter
function drops the pipe lock, thereby allowing F_SETPIPE_SZ change them.
Without this, pipe_write() may subsequently miscalculate the array
indices and pipe fullness, leading to an oops like the following:

  BUG: KASAN: slab-out-of-bounds in pipe_write+0xc25/0xe10 fs/pipe.c:481
  Write of size 8 at addr ffff8880771167a8 by task syz-executor.3/7987
  ...
  CPU: 1 PID: 7987 Comm: syz-executor.3 Not tainted 5.4.0-rc2-syzkaller #0
  ...
  Call Trace:
    pipe_write+0xc25/0xe10 fs/pipe.c:481
    call_write_iter include/linux/fs.h:1895 [inline]
    new_sync_write+0x3fd/0x7e0 fs/read_write.c:483
    __vfs_write+0x94/0x110 fs/read_write.c:496
    vfs_write+0x18a/0x520 fs/read_write.c:558
    ksys_write+0x105/0x220 fs/read_write.c:611
    __do_sys_write fs/read_write.c:623 [inline]
    __se_sys_write fs/read_write.c:620 [inline]
    __x64_sys_write+0x6e/0xb0 fs/read_write.c:620
    do_syscall_64+0xca/0x5d0 arch/x86/entry/common.c:290
    entry_SYSCALL_64_after_hwframe+0x49/0xbe

This is not a problem for pipe_read() as the mask is recalculated on
each pass of the loop, after pipe_wait() has been called.

Fixes: 8cefc107 ("pipe: Use head and tail pointers for the ring, not cursor and length")
Reported-by: syzbot+838eb0878ffd51f27c41@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Eric Biggers <ebiggers@kernel.org>
[ Changed it to use a temporary variable 'mask' to avoid long lines -Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

An assertion check was added to pipe_poll() to make sure that the ring
occupancy isn't seen to overflow the ring size.  However, since no locks
are held when the three values are read, it is possible for F_SETPIPE_SZ
to intervene and muck up the calculation, thereby causing the oops.

Fix this by simply removing the assertion and accepting that the
calculation might be approximate.

Note that the previous code also had a similar issue, though there was
no assertion check, since the occupancy counter and the ring size were
not read with a lock held, so it's possible that the poll check might
have malfunctioned then too.

Also wake up all the waiters so that they can reissue their checks if
there was a competing read or write.

Fixes: 8cefc107 ("pipe: Use head and tail pointers for the ring, not cursor and length")
Reported-by: syzbot+d37abaade33a934f16f2@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This is mostly to reorder the entries as they've moved in the Kconfig
hierarchies. Doing this periodically (but not very often) simplifies
conflict resolution for new options, etc.

Link: https://lore.kernel.org/r/20191205211438.27552-2-olof@lixom.netSigned-off-by: Olof Johansson <olof@lixom.net>

This is mostly to reorder the entries as they've moved in the Kconfig
hierarchies. Doing this periodically (but not very often) simplifies
conflict resolution for new options, etc.

Link: https://lore.kernel.org/r/20191205211438.27552-3-olof@lixom.netSigned-off-by: Olof Johansson <olof@lixom.net>

Pull GFS2 updates from Andreas Gruenbacher:
 "Bob's extensive filesystem withdrawal and recovery testing:
   - don't write log headers after file system withdraw
   - clean up iopen glock mess in gfs2_create_inode
   - close timing window with GLF_INVALIDATE_IN_PROGRESS
   - abort gfs2_freeze if io error is seen
   - don't loop forever in gfs2_freeze if withdrawn
   - fix infinite loop in gfs2_ail1_flush on io error
   - introduce function gfs2_withdrawn
   - fix glock reference problem in gfs2_trans_remove_revoke

  Filesystems with a block size smaller than the page size:
   - fix end-of-file handling in gfs2_page_mkwrite
   - improve mmap write vs. punch_hole consistency

  Other:
   - remove active journal side effect from gfs2_write_log_header
   - multi-block allocations in gfs2_page_mkwrite

  Minor cleanups and coding style fixes:
   - remove duplicate call from gfs2_create_inode
   - make gfs2_log_shutdown static
   - make gfs2_fs_parameters static
   - some whitespace cleanups
   - removed unnecessary semicolon"

* tag 'gfs2-for-5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2:
  gfs2: Don't write log headers after file system withdraw
  gfs2: Remove duplicate call from gfs2_create_inode
  gfs2: clean up iopen glock mess in gfs2_create_inode
  gfs2: Close timing window with GLF_INVALIDATE_IN_PROGRESS
  gfs2: Abort gfs2_freeze if io error is seen
  gfs2: Don't loop forever in gfs2_freeze if withdrawn
  gfs2: fix infinite loop in gfs2_ail1_flush on io error
  gfs2: Introduce function gfs2_withdrawn
  gfs2: fix glock reference problem in gfs2_trans_remove_revoke
  gfs2: make gfs2_log_shutdown static
  gfs2: Remove active journal side effect from gfs2_write_log_header
  gfs2: Fix end-of-file handling in gfs2_page_mkwrite
  gfs2: Multi-block allocations in gfs2_page_mkwrite
  gfs2: Improve mmap write vs. punch_hole consistency
  gfs2: make gfs2_fs_parameters static
  gfs2: Some whitespace cleanups
  gfs2: removed unnecessary semicolon

This brings in the mainline tree right after armsoc contents was merged
this release cycle, so that we can re-run savedefconfig, etc.
Signed-off-by: Olof Johansson <olof@lixom.net>

Pull ceph updates from Ilya Dryomov:
 "The two highlights are a set of improvements to how rbd read-only
  mappings are handled and a conversion to the new mount API (slightly
  complicated by the fact that we had a common option parsing framework
  that called out into rbd and the filesystem instead of them calling
  into it).

  Also included a few scattered fixes and a MAINTAINERS update for rbd,
  adding Dongsheng as a reviewer"

* tag 'ceph-for-5.5-rc1' of git://github.com/ceph/ceph-client:
  libceph, rbd, ceph: convert to use the new mount API
  rbd: ask for a weaker incompat mask for read-only mappings
  rbd: don't query snapshot features
  rbd: remove snapshot existence validation code
  rbd: don't establish watch for read-only mappings
  rbd: don't acquire exclusive lock for read-only mappings
  rbd: disallow read-write partitions on images mapped read-only
  rbd: treat images mapped read-only seriously
  rbd: introduce RBD_DEV_FLAG_READONLY
  rbd: introduce rbd_is_snap()
  ceph: don't leave ino field in ceph_mds_request_head uninitialized
  ceph: tone down loglevel on ceph_mdsc_build_path warning
  rbd: update MAINTAINERS info
  ceph: fix geting random mds from mdsmap
  rbd: fix spelling mistake "requeueing" -> "requeuing"
  ceph: make several helper accessors take const pointers
  libceph: drop unnecessary check from dispatch() in mon_client.c