Expose a new system call allowing each thread to register one userspace
memory area to be used as an ABI between kernel and user-space for two
purposes: user-space restartable sequences and quick access to read the
current CPU number value from user-space.

* Restartable sequences (per-cpu atomics)

Restartables sequences allow user-space to perform update operations on
per-cpu data without requiring heavy-weight atomic operations.

The restartable critical sections (percpu atomics) work has been started
by Paul Turner and Andrew Hunter. It lets the kernel handle restart of
critical sections. [1] [2] The re-implementation proposed here brings a
few simplifications to the ABI which facilitates porting to other
architectures and speeds up the user-space fast path.

Here are benchmarks of various rseq use-cases.

Test hardware:

arm32: ARMv7 Processor rev 4 (v7l) "Cubietruck", 2-core
x86-64: Intel E5-2630 v3@2.40GHz, 16-core, hyperthreading

The following benchmarks were all performed on a single thread.

* Per-CPU statistic counter increment

                getcpu+atomic (ns/op)    rseq (ns/op)    speedup
arm32:                344.0                 31.4          11.0
x86-64:                15.3                  2.0           7.7

* LTTng-UST: write event 32-bit header, 32-bit payload into tracer
             per-cpu buffer

                getcpu+atomic (ns/op)    rseq (ns/op)    speedup
arm32:               2502.0                 2250.0         1.1
x86-64:               117.4                   98.0         1.2

* liburcu percpu: lock-unlock pair, dereference, read/compare word

                getcpu+atomic (ns/op)    rseq (ns/op)    speedup
arm32:                751.0                 128.5          5.8
x86-64:                53.4                  28.6          1.9

* jemalloc memory allocator adapted to use rseq

Using rseq with per-cpu memory pools in jemalloc at Facebook (based on
rseq 2016 implementation):

The production workload response-time has 1-2% gain avg. latency, and
the P99 overall latency drops by 2-3%.

* Reading the current CPU number

Speeding up reading the current CPU number on which the caller thread is
running is done by keeping the current CPU number up do date within the
cpu_id field of the memory area registered by the thread. This is done
by making scheduler preemption set the TIF_NOTIFY_RESUME flag on the
current thread. Upon return to user-space, a notify-resume handler
updates the current CPU value within the registered user-space memory
area. User-space can then read the current CPU number directly from
memory.

Keeping the current cpu id in a memory area shared between kernel and
user-space is an improvement over current mechanisms available to read
the current CPU number, which has the following benefits over
alternative approaches:

- 35x speedup on ARM vs system call through glibc
- 20x speedup on x86 compared to calling glibc, which calls vdso
  executing a "lsl" instruction,
- 14x speedup on x86 compared to inlined "lsl" instruction,
- Unlike vdso approaches, this cpu_id value can be read from an inline
  assembly, which makes it a useful building block for restartable
  sequences.
- The approach of reading the cpu id through memory mapping shared
  between kernel and user-space is portable (e.g. ARM), which is not the
  case for the lsl-based x86 vdso.

On x86, yet another possible approach would be to use the gs segment
selector to point to user-space per-cpu data. This approach performs
similarly to the cpu id cache, but it has two disadvantages: it is
not portable, and it is incompatible with existing applications already
using the gs segment selector for other purposes.

Benchmarking various approaches for reading the current CPU number:

ARMv7 Processor rev 4 (v7l)
Machine model: Cubietruck
- Baseline (empty loop):                                    8.4 ns
- Read CPU from rseq cpu_id:                               16.7 ns
- Read CPU from rseq cpu_id (lazy register):               19.8 ns
- glibc 2.19-0ubuntu6.6 getcpu:                           301.8 ns
- getcpu system call:                                     234.9 ns

x86-64 Intel(R) Xeon(R) CPU E5-2630 v3 @ 2.40GHz:
- Baseline (empty loop):                                    0.8 ns
- Read CPU from rseq cpu_id:                                0.8 ns
- Read CPU from rseq cpu_id (lazy register):                0.8 ns
- Read using gs segment selector:                           0.8 ns
- "lsl" inline assembly:                                   13.0 ns
- glibc 2.19-0ubuntu6 getcpu:                              16.6 ns
- getcpu system call:                                      53.9 ns

- Speed (benchmark taken on v8 of patchset)

Running 10 runs of hackbench -l 100000 seems to indicate, contrary to
expectations, that enabling CONFIG_RSEQ slightly accelerates the
scheduler:

Configuration: 2 sockets * 8-core Intel(R) Xeon(R) CPU E5-2630 v3 @
2.40GHz (directly on hardware, hyperthreading disabled in BIOS, energy
saving disabled in BIOS, turboboost disabled in BIOS, cpuidle.off=1
kernel parameter), with a Linux v4.6 defconfig+localyesconfig,
restartable sequences series applied.

* CONFIG_RSEQ=n

avg.:      41.37 s
std.dev.:   0.36 s

* CONFIG_RSEQ=y

avg.:      40.46 s
std.dev.:   0.33 s

- Size

On x86-64, between CONFIG_RSEQ=n/y, the text size increase of vmlinux is
567 bytes, and the data size increase of vmlinux is 5696 bytes.

[1] https://lwn.net/Articles/650333/
[2] http://www.linuxplumbersconf.org/2013/ocw/system/presentations/1695/original/LPC%20-%20PerCpu%20Atomics.pdfSigned-off-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Watson <davejwatson@fb.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Chris Lameter <cl@linux.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Andrew Hunter <ahh@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Maurer <bmaurer@fb.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-api@vger.kernel.org
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20151027235635.16059.11630.stgit@pjt-glaptop.roam.corp.google.com
Link: http://lkml.kernel.org/r/20150624222609.6116.86035.stgit@kitami.mtv.corp.google.com
Link: https://lkml.kernel.org/r/20180602124408.8430-3-mathieu.desnoyers@efficios.com

Provide helper macros for fields which represent pointers in
kernel-userspace ABI. This facilitates handling of 32-bit
user-space by 64-bit kernels by defining those fields as
32-bit 0-padding and 32-bit integer on 32-bit architectures,
which allows the kernel to treat those as 64-bit integers.
The order of padding and 32-bit integer depends on the
endianness.
Signed-off-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Watson <davejwatson@fb.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Chris Lameter <cl@linux.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Andrew Hunter <ahh@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Maurer <bmaurer@fb.com>
Cc: linux-api@vger.kernel.org
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lkml.kernel.org/r/20180602124408.8430-2-mathieu.desnoyers@efficios.com

Pull x86 hyperv updates from Thomas Gleixner:
 "A set of commits to enable APIC enlightenment when running as a guest
  on Microsoft HyperV.

  This accelerates the APIC access with paravirtualization techniques,
  which are called enlightenments on Hyper-V"

* 'x86-hyperv-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/Hyper-V/hv_apic: Build the Hyper-V APIC conditionally
  x86/Hyper-V/hv_apic: Include asm/apic.h
  X86/Hyper-V: Consolidate the allocation of the hypercall input page
  X86/Hyper-V: Consolidate code for converting cpumask to vpset
  X86/Hyper-V: Enhanced IPI enlightenment
  X86/Hyper-V: Enable IPI enlightenments
  X86/Hyper-V: Enlighten APIC access

Pull x86 cache resource controller updates from Thomas Gleixner:
 "An update for the Intel Resource Director Technolgy (RDT) which adds a
  feedback driven software controller to runtime adjust the bandwidth
  allocation MSRs.

  This makes the allocations more accurate and allows to use bandwidth
  values in understandable units (MB/s) instead of using percentage
  based allocations as the original, still available, interface.

  The software controller can be enabled with a new mount option for the
  resctrl filesystem"

* 'x86-cache-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/intel_rdt/mba_sc: Feedback loop to dynamically update mem bandwidth
  x86/intel_rdt/mba_sc: Prepare for feedback loop
  x86/intel_rdt/mba_sc: Add schemata support
  x86/intel_rdt/mba_sc: Add initialization support
  x86/intel_rdt/mba_sc: Enable/disable MBA software controller
  x86/intel_rdt/mba_sc: Documentation for MBA software controller(mba_sc)

Pull time/Y2038 updates from Thomas Gleixner:

 - Consolidate SySV IPC UAPI headers

 - Convert SySV IPC to the new COMPAT_32BIT_TIME mechanism

 - Cleanup the core interfaces and standardize on the ktime_get_* naming
   convention.

 - Convert the X86 platform ops to timespec64

 - Remove the ugly temporary timespec64 hack

* 'timers-2038-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits)
  x86: Convert x86_platform_ops to timespec64
  timekeeping: Add more coarse clocktai/boottime interfaces
  timekeeping: Add ktime_get_coarse_with_offset
  timekeeping: Standardize on ktime_get_*() naming
  timekeeping: Clean up ktime_get_real_ts64
  timekeeping: Remove timespec64 hack
  y2038: ipc: Redirect ipc(SEMTIMEDOP, ...) to compat_ksys_semtimedop
  y2038: ipc: Enable COMPAT_32BIT_TIME
  y2038: ipc: Use __kernel_timespec
  y2038: ipc: Report long times to user space
  y2038: ipc: Use ktime_get_real_seconds consistently
  y2038: xtensa: Extend sysvipc data structures
  y2038: powerpc: Extend sysvipc data structures
  y2038: sparc: Extend sysvipc data structures
  y2038: parisc: Extend sysvipc data structures
  y2038: mips: Extend sysvipc data structures
  y2038: arm64: Extend sysvipc compat data structures
  y2038: s390: Remove unneeded ipc uapi header files
  y2038: ia64: Remove unneeded ipc uapi header files
  y2038: alpha: Remove unneeded ipc uapi header files
  ...

Pull timers and timekeeping updates from Thomas Gleixner:

 - Core infrastucture work for Y2038 to address the COMPAT interfaces:

     + Add a new Y2038 safe __kernel_timespec and use it in the core
       code

     + Introduce config switches which allow to control the various
       compat mechanisms

     + Use the new config switch in the posix timer code to control the
       32bit compat syscall implementation.

 - Prevent bogus selection of CPU local clocksources which causes an
   endless reselection loop

 - Remove the extra kthread in the clocksource code which has no value
   and just adds another level of indirection

 - The usual bunch of trivial updates, cleanups and fixlets all over the
   place

 - More SPDX conversions

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
  clocksource/drivers/mxs_timer: Switch to SPDX identifier
  clocksource/drivers/timer-imx-tpm: Switch to SPDX identifier
  clocksource/drivers/timer-imx-gpt: Switch to SPDX identifier
  clocksource/drivers/timer-imx-gpt: Remove outdated file path
  clocksource/drivers/arc_timer: Add comments about locking while read GFRC
  clocksource/drivers/mips-gic-timer: Add pr_fmt and reword pr_* messages
  clocksource/drivers/sprd: Fix Kconfig dependency
  clocksource: Move inline keyword to the beginning of function declarations
  timer_list: Remove unused function pointer typedef
  timers: Adjust a kernel-doc comment
  tick: Prefer a lower rating device only if it's CPU local device
  clocksource: Remove kthread
  time: Change nanosleep to safe __kernel_* types
  time: Change types to new y2038 safe __kernel_* types
  time: Fix get_timespec64() for y2038 safe compat interfaces
  time: Add new y2038 safe __kernel_timespec
  posix-timers: Make compat syscalls depend on CONFIG_COMPAT_32BIT_TIME
  time: Introduce CONFIG_COMPAT_32BIT_TIME
  time: Introduce CONFIG_64BIT_TIME in architectures
  compat: Enable compat_get/put_timespec64 always
  ...

Pull x86 RAS updates from Thomas Gleixner:

 - Fix a stack out of bounds write in the MCE error injection code.

 - Avoid IPIs during CPU hotplug to read the MCx_MISC block address from
   a remote CPU. That's fragile and pointless because the block
   addresses are the same on all CPUs. So they can be read once and
   local.

 - Add support for MCE broadcasting on newer VIA Centaur CPUs.

* 'ras-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/MCE/AMD: Read MCx_MISC block addresses on any CPU
  x86/MCE: Fix stack out-of-bounds write in mce-inject.c: Flags_read()
  x86/MCE: Enable MCE broadcasting on new Centaur CPUs

Pull irq updates from Thomas Gleixner:

 - Consolidation of softirq pending:

   The softirq mask and its accessors/mutators have many implementations
   scattered around many architectures. Most do the same things
   consisting in a field in a per-cpu struct (often irq_cpustat_t)
   accessed through per-cpu ops. We can provide instead a generic
   efficient version that most of them can use. In fact s390 is the only
   exception because the field is stored in lowcore.

 - Support for level!?! triggered MSI (ARM)

   Over the past couple of years, we've seen some SoCs coming up with
   ways of signalling level interrupts using a new flavor of MSIs, where
   the MSI controller uses two distinct messages: one that raises a
   virtual line, and one that lowers it. The target MSI controller is in
   charge of maintaining the state of the line.

   This allows for a much simplified HW signal routing (no need to have
   hundreds of discrete lines to signal level interrupts if you already
   have a memory bus), but results in a departure from the current idea
   the kernel has of MSIs.

 - Support for Meson-AXG GPIO irqchip

 - Large stm32 irqchip rework (suspend/resume, hierarchical domains)

 - More SPDX conversions

* 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
  ARM: dts: stm32: Add exti support to stm32mp157 pinctrl
  ARM: dts: stm32: Add exti support for stm32mp157c
  pinctrl/stm32: Add irq_eoi for stm32gpio irqchip
  irqchip/stm32: Add suspend/resume support for hierarchy domain
  irqchip/stm32: Add stm32mp1 support with hierarchy domain
  irqchip/stm32: Prepare common functions
  irqchip/stm32: Add host and driver data structures
  irqchip/stm32: Add suspend support
  irqchip/stm32: Add falling pending register support
  irqchip/stm32: Checkpatch fix
  irqchip/stm32: Optimizes and cleans up stm32-exti irq_domain
  irqchip/meson-gpio: Add support for Meson-AXG SoCs
  dt-bindings: interrupt-controller: New binding for Meson-AXG SoC
  dt-bindings: interrupt-controller: Fix the double quotes
  softirq/s390: Move default mutators of overwritten softirq mask to s390
  softirq/x86: Switch to generic local_softirq_pending() implementation
  softirq/sparc: Switch to generic local_softirq_pending() implementation
  softirq/powerpc: Switch to generic local_softirq_pending() implementation
  softirq/parisc: Switch to generic local_softirq_pending() implementation
  softirq/ia64: Switch to generic local_softirq_pending() implementation
  ...

Pull x86 dax updates from Ingo Molnar:
 "This contains x86 memcpy_mcsafe() fault handling improvements the
  nvdimm tree would like to make more use of"

* 'x86-dax-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/asm/memcpy_mcsafe: Define copy_to_iter_mcsafe()
  x86/asm/memcpy_mcsafe: Add write-protection-fault handling
  x86/asm/memcpy_mcsafe: Return bytes remaining
  x86/asm/memcpy_mcsafe: Add labels for __memcpy_mcsafe() write fault handling
  x86/asm/memcpy_mcsafe: Remove loop unrolling

Pull x86 debug updates from Ingo Molnar:
 "This contains the x86 oops code printing reorganization and cleanups
  from Borislav Betkov, with a particular focus in enhancing opcode
  dumping all around"

* 'x86-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/dumpstack: Explain the reasoning for the prologue and buffer size
  x86/dumpstack: Save first regs set for the executive summary
  x86/dumpstack: Add a show_ip() function
  x86/fault: Dump user opcode bytes on fatal faults
  x86/dumpstack: Add loglevel argument to show_opcodes()
  x86/dumpstack: Improve opcodes dumping in the code section
  x86/dumpstack: Carve out code-dumping into a function
  x86/dumpstack: Unexport oops_begin()
  x86/dumpstack: Remove code_bytes

Pull x86 cleanups from Ingo Molnar:
 "Misc cleanups"

* 'x86-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/apm: Fix spelling mistake: "caculate" -> "calculate"
  x86/mtrr: Rename main.c to mtrr.c and remove duplicate prefixes
  x86: Remove pr_fmt duplicate logging prefixes
  x86/early-quirks: Rename duplicate define of dev_err
  x86/bpf: Clean up non-standard comments, to make the code more readable

Pull x86 build updates from Ingo Molnar:
 "A handful of build system (Makefile, linker script) cleanups by
  Masahiro Yamada"

* 'x86-build-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/build/vdso: Put generated linker scripts to $(obj)/
  x86/build/vdso: Remove unnecessary export in Makefile
  x86/build/vdso: Remove unused $(vobjs-nox32) in Makefile
  x86/build: Remove no-op macro VMLINUX_SYMBOL()

Pull x86 asm updates from Ingo Molnar:

 - better support (non-atomic) 64-bit readq()/writeq() variants (Andy
   Shevchenko)

 - __clear_user() micro-optimization (Alexey Dobriyan)

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/io: Define readq()/writeq() to use 64-bit type
  x86/asm/64: Micro-optimize __clear_user() - Use immediate constants

Pull x86 boot updates from Ingo Molnar:

 - Centaur CPU updates (David Wang)

 - AMD and other CPU topology enumeration improvements and fixes
   (Borislav Petkov, Thomas Gleixner, Suravee Suthikulpanit)

 - Continued 5-level paging work (Kirill A. Shutemov)

* 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/mm: Mark __pgtable_l5_enabled __initdata
  x86/mm: Mark p4d_offset() __always_inline
  x86/mm: Introduce the 'no5lvl' kernel parameter
  x86/mm: Stop pretending pgtable_l5_enabled is a variable
  x86/mm: Unify pgtable_l5_enabled usage in early boot code
  x86/boot/compressed/64: Fix trampoline page table address calculation
  x86/CPU: Move x86_cpuinfo::x86_max_cores assignment to detect_num_cpu_cores()
  x86/Centaur: Report correct CPU/cache topology
  x86/CPU: Move cpu_detect_cache_sizes() into init_intel_cacheinfo()
  x86/CPU: Make intel_num_cpu_cores() generic
  x86/CPU: Move cpu local function declarations to local header
  x86/CPU/AMD: Derive CPU topology from CPUID function 0xB when available
  x86/CPU: Modify detect_extended_topology() to return result
  x86/CPU/AMD: Calculate last level cache ID from number of sharing threads
  x86/CPU: Rename intel_cacheinfo.c to cacheinfo.c
  perf/events/amd/uncore: Fix amd_uncore_llc ID to use pre-defined cpu_llc_id
  x86/CPU/AMD: Have smp_num_siblings and cpu_llc_id always be present
  x86/Centaur: Initialize supported CPU features properly

Pull scheduler updates from Ingo Molnar:

 - power-aware scheduling improvements (Patrick Bellasi)

 - NUMA balancing improvements (Mel Gorman)

 - vCPU scheduling fixes (Rohit Jain)

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Update util_est before updating schedutil
  sched/cpufreq: Modify aggregate utilization to always include blocked FAIR utilization
  sched/deadline/Documentation: Add overrun signal and GRUB-PA documentation
  sched/core: Distinguish between idle_cpu() calls based on desired effect, introduce available_idle_cpu()
  sched/wait: Include <linux/wait.h> in <linux/swait.h>
  sched/numa: Stagger NUMA balancing scan periods for new threads
  sched/core: Don't schedule threads on pre-empted vCPUs
  sched/fair: Avoid calling sync_entity_load_avg() unnecessarily
  sched/fair: Rearrange select_task_rq_fair() to optimize it

Pull perf updates from Ingo Molnar:
 "Kernel side changes:

   - x86 Intel uncore driver cleanups and enhancements (Kan Liang)

   - group scheduling and other fixes (Song Liu

   - store frame pointer in the sample traces for better profiling
     (Alexey Budankov)

   - compat fixes/enhancements (Eugene Syromiatnikov)

  Tooling side changes, which you can build and install in a single step
  via:

      make -C tools/perf clean install

  perf annotate:

   - Support 'perf annotate --group' for non-explicit recorded event
     "groups", showing multiple columns, one for each event, just like
     when dealing with explicit event groups (those enclosed with {})
     (Jin Yao)

   - Record min/max LBR cycles (>= Skylake) and add 'perf annotate' TUI
     hotkey to show it (c) (Jin Yao)

  perf bpf:

   - Add infrastructure to help in writing eBPF C programs to be used
     with '-e name.c' type events in tools such as 'record' and 'trace',
     with headers for common constructs and an examples directory that
     will get populated as we add more such helpers and the 'perf bpf'
     (Arnaldo Carvalho de Melo)

  perf stat:

   - Display time in precision based on std deviation (Jiri Olsa)

   - Add --table option to display time of each run (Jiri Olsa)

   - Display length strings of each run for --table option (Jiri Olsa)

  perf buildid-cache:

   - Add --list and --purge-all options (Ravi Bangoria)

  perf test:

   - Let 'perf test list' display subtests (Hendrik Brueckner)

  perf pti:

   - Create extra kernel maps to help in decoding samples in x86 PTI
     entry trampolines (Adrian Hunter)

   - Copy x86 PTI entry trampoline sections in the kcore copy used for
     annotation and intel_pt CPU traces decoding (Adrian Hunter)

  ... and a lot of other fixes, enhancements and cleanups I did not
  list, see the shortlog and git log for details"

* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (111 commits)
  perf/x86/intel/uncore: Clean up client IMC uncore
  perf/x86/intel/uncore: Expose uncore_pmu_event*() functions
  perf/x86/intel/uncore: Support IIO free-running counters on SKX
  perf/x86/intel/uncore: Add infrastructure for free running counters
  perf/x86/intel/uncore: Add new data structures for free running counters
  perf/x86/intel/uncore: Correct fixed counter index check in generic code
  perf/x86/intel/uncore: Correct fixed counter index check for NHM
  perf/x86/intel/uncore: Introduce customized event_read() for client IMC uncore
  perf/x86: Store user space frame-pointer value on a sample
  perf/core: Wire up compat PERF_EVENT_IOC_QUERY_BPF, PERF_EVENT_IOC_MODIFY_ATTRIBUTES
  perf/core: Fix bad use of igrab()
  perf/core: Fix group scheduling with mixed hw and sw events
  perf kcore_copy: Amend the offset of sections that remap kernel text
  perf kcore_copy: Copy x86 PTI entry trampoline sections
  perf kcore_copy: Get rid of kernel_map
  perf kcore_copy: Iterate phdrs
  perf kcore_copy: Layout sections
  perf kcore_copy: Calculate offset from phnum
  perf kcore_copy: Keep a count of phdrs
  perf kcore_copy: Keep phdr data in a list
  ...

Pull perf tooling fixes from Ingo Molnar:
 "Leftover perf tooling fixes from the v4.17 cycle: they sync up updated
  ABI headers with their tooling versions"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf tools intel-pt-decoder: Update insn.h from the kernel sources
  tools headers: Sync x86 cpufeatures.h with the kernel sources
  tools headers: Synchronize prctl.h ABI header
  perf trace beauty prctl: Default header_dir to cwd to work without parms

Pull locking updates from Ingo Molnar:

 - Lots of tidying up changes all across the map for Linux's formal
   memory/locking-model tooling, by Alan Stern, Akira Yokosawa, Andrea
   Parri, Paul E. McKenney and SeongJae Park.

   Notable changes beyond an overall update in the tooling itself is the
   tidying up of spin_is_locked() semantics, which spills over into the
   kernel proper as well.

 - qspinlock improvements: the locking algorithm now guarantees forward
   progress whereas the previous implementation in mainline could starve
   threads indefinitely in cmpxchg() loops. Also other related cleanups
   to the qspinlock code (Will Deacon)

 - misc smaller improvements, cleanups and fixes all across the locking
   subsystem

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (51 commits)
  locking/rwsem: Simplify the is-owner-spinnable checks
  tools/memory-model: Add reference for 'Simplifying ARM concurrency'
  tools/memory-model: Update ASPLOS information
  MAINTAINERS, tools/memory-model: Update e-mail address for Andrea Parri
  tools/memory-model: Fix coding style in 'lock.cat'
  tools/memory-model: Remove out-of-date comments and code from lock.cat
  tools/memory-model: Improve mixed-access checking in lock.cat
  tools/memory-model: Improve comments in lock.cat
  tools/memory-model: Remove duplicated code from lock.cat
  tools/memory-model: Flag "cumulativity" and "propagation" tests
  tools/memory-model: Add model support for spin_is_locked()
  tools/memory-model: Add scripts to test memory model
  tools/memory-model: Fix coding style in 'linux-kernel.def'
  tools/memory-model: Model 'smp_store_mb()'
  tools/memory-order: Update the cheat-sheet to show that smp_mb__after_atomic() orders later RMW operations
  tools/memory-order: Improve key for SELF and SV
  tools/memory-model: Fix cheat sheet typo
  tools/memory-model: Update required version of herdtools7
  tools/memory-model: Redefine rb in terms of rcu-fence
  tools/memory-model: Rename link and rcu-path to rcu-link and rb
  ...

Pull EFI updates from Ingo Molnar:

 - decode x86 CPER data (Yazen Ghannam)

 - ignore unrealistically large option ROMs (Hans de Goede)

 - initialize UEFI secure boot state during Xen dom0 boot (Daniel Kiper)

 - additional minor tweaks and fixes.

* 'efi-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  efi/capsule-loader: Don't output reset log when reset flags are not set
  efi/x86: Ignore unrealistically large option ROMs
  efi/x86: Fold __setup_efi_pci32() and __setup_efi_pci64() into one function
  efi: Align efi_pci_io_protocol typedefs to type naming convention
  efi/libstub/tpm: Make function efi_retrieve_tpm2_eventlog_1_2() static
  efi: Decode IA32/X64 Context Info structure
  efi: Decode IA32/X64 MS Check structure
  efi: Decode additional IA32/X64 Bus Check fields
  efi: Decode IA32/X64 Cache, TLB, and Bus Check structures
  efi: Decode UEFI-defined IA32/X64 Error Structure GUIDs
  efi: Decode IA32/X64 Processor Error Info Structure
  efi: Decode IA32/X64 Processor Error Section
  efi: Fix IA32/X64 Processor Error Record definition
  efi/cper: Remove the INDENT_SP silliness
  x86/xen/efi: Initialize UEFI secure boot state during dom0 boot

Pull RCU updates from Ingo Molnar:

 - updates to the handling of expedited grace periods

 - updates to reduce lock contention in the rcu_node combining tree

   [ These are in preparation for the consolidation of RCU-bh,
     RCU-preempt, and RCU-sched into a single flavor, which was
     requested by Linus in response to a security flaw whose root cause
     included confusion between the multiple flavors of RCU ]

 - torture-test updates that save their users some time and effort

 - miscellaneous fixes

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits)
  rcu/x86: Provide early rcu_cpu_starting() callback
  torture: Make kvm-find-errors.sh find build warnings
  rcutorture: Abbreviate kvm.sh summary lines
  rcutorture: Print end-of-test state in kvm.sh summary
  rcutorture: Print end-of-test state
  torture: Fold parse-torture.sh into parse-console.sh
  torture: Add a script to edit output from failed runs
  rcu: Update list of rcu_future_grace_period() trace events
  rcu: Drop early GP request check from rcu_gp_kthread()
  rcu: Simplify and inline cpu_needs_another_gp()
  rcu: The rcu_gp_cleanup() function does not need cpu_needs_another_gp()
  rcu: Make rcu_start_this_gp() check for out-of-range requests
  rcu: Add funnel locking to rcu_start_this_gp()
  rcu: Make rcu_start_future_gp() caller select grace period
  rcu: Inline rcu_start_gp_advanced() into rcu_start_future_gp()
  rcu: Clear request other than RCU_GP_FLAG_INIT at GP end
  rcu: Cleanup, don't put ->completed into an int
  rcu: Switch __rcu_process_callbacks() to rcu_accelerate_cbs()
  rcu: Avoid __call_rcu_core() root rcu_node ->lock acquisition
  rcu: Make rcu_migrate_callbacks wake GP kthread when needed
  ...

Pull m68k updates from Geert Uytterhoeven:

 - a few time-related fixes:
     - off-by-one calendar month on some classes of machines
     - Y2038 preparation

 - build fix for ndelay() being called with a 64-bit type

 - revive 64-bit get_user(), which is used by some Android code

 - defconfig updates

 - fix for a long-standing fatal bug in iounmap() on '020/030, which was
   actually fixed in 2.4.23, but never in 2.5.x and later

 - default DMA mask to avoid warning splats

 - minor fixes and cleanups

* tag 'm68k-for-v4.18-tag1' of git://git.kernel.org/pub/scm/linux/kernel/git/geert/linux-m68k:
  m68k: Set default dma mask for platform devices
  m68k/mm: Adjust VM area to be unmapped by gap size for __iounmap()
  m68k/defconfig: Update defconfigs for v4.17-rc3
  m68k/uaccess: Revive 64-bit get_user()
  m68k: Implement ndelay() as an inline function to force type checking/casting
  zorro: Add a blank line after declarations
  m68k: Use read_persistent_clock64() consistently
  m68k: Fix off-by-one calendar month
  m68k: Fix style, spelling, and grammar in siginfo_build_tests()
  m68k/mac: Fix SWIM memory resource end address

Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull siginfo updates from Eric Biederman:
 "This set of changes close the known issues with setting si_code to an
  invalid value, and with not fully initializing struct siginfo. There
  remains work to do on nds32, arc, unicore32, powerpc, arm, arm64, ia64
  and x86 to get the code that generates siginfo into a simpler and more
  maintainable state. Most of that work involves refactoring the signal
  handling code and thus careful code review.

  Also not included is the work to shrink the in kernel version of
  struct siginfo. That depends on getting the number of places that
  directly manipulate struct siginfo under control, as it requires the
  introduction of struct kernel_siginfo for the in kernel things.

  Overall this set of changes looks like it is making good progress, and
  with a little luck I will be wrapping up the siginfo work next
  development cycle"

* 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (46 commits)
  signal/sh: Stop gcc warning about an impossible case in do_divide_error
  signal/mips: Report FPE_FLTUNK for undiagnosed floating point exceptions
  signal/um: More carefully relay signals in relay_signal.
  signal: Extend siginfo_layout with SIL_FAULT_{MCEERR|BNDERR|PKUERR}
  signal: Remove unncessary #ifdef SEGV_PKUERR in 32bit compat code
  signal/signalfd: Add support for SIGSYS
  signal/signalfd: Remove __put_user from signalfd_copyinfo
  signal/xtensa: Use force_sig_fault where appropriate
  signal/xtensa: Consistenly use SIGBUS in do_unaligned_user
  signal/um: Use force_sig_fault where appropriate
  signal/sparc: Use force_sig_fault where appropriate
  signal/sparc: Use send_sig_fault where appropriate
  signal/sh: Use force_sig_fault where appropriate
  signal/s390: Use force_sig_fault where appropriate
  signal/riscv: Replace do_trap_siginfo with force_sig_fault
  signal/riscv: Use force_sig_fault where appropriate
  signal/parisc: Use force_sig_fault where appropriate
  signal/parisc: Use force_sig_mceerr where appropriate
  signal/openrisc: Use force_sig_fault where appropriate
  signal/nios2: Use force_sig_fault where appropriate
  ...

Merge branch 'userns-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull userns updates from Eric Biederman:
 "This is the last couple of vfs bits to enable root in a user namespace
  to mount and manipulate a filesystem with backing store (AKA not a
  virtual filesystem like proc, but a filesystem where the unprivileged
  user controls the content). The target filesystem for this work is
  fuse, and Miklos should be sending you the pull request for the fuse
  bits this merge window.

  The two key patches are "evm: Don't update hmacs in user ns mounts"
  and "vfs: Don't allow changing the link count of an inode with an
  invalid uid or gid". Those close small gaps in the vfs that would be a
  problem if an unprivileged fuse filesystem is mounted.

  The rest of the changes are things that are now safe to allow a root
  user in a user namespace to do with a filesystem they have mounted.
  The most interesting development is that remount is now safe"

* 'userns-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  fs: Allow CAP_SYS_ADMIN in s_user_ns to freeze and thaw filesystems
  capabilities: Allow privileged user in s_user_ns to set security.* xattrs
  fs: Allow superblock owner to access do_remount_sb()
  fs: Allow superblock owner to replace invalid owners of inodes
  vfs: Allow userns root to call mknod on owned filesystems.
  vfs: Don't allow changing the link count of an inode with an invalid uid or gid
  evm: Don't update hmacs in user ns mounts

Pull cifs updates from Steve French:

 - smb3 fixes for stable

 - addition of ftrace hooks for cifs.ko

 - improvements in compounding and smbdirect (rdma)

* tag '4.18-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6: (38 commits)
  CIFS: Add support for direct pages in wdata
  CIFS: Use offset when reading pages
  CIFS: Add support for direct pages in rdata
  cifs: update multiplex loop to handle compounded responses
  cifs: remove header_preamble_size where it is always 0
  cifs: remove struct smb2_hdr
  CIFS: 511c54a2 adds a check for session expiry, status STATUS_NETWORK_SESSION_EXPIRED, however the server can also respond with STATUS_USER_SESSION_DELETED in cases where the session has been idle for some time and the server reaps the session to recover resources.
  cifs: change smb2_get_data_area_len to take a smb2_sync_hdr as argument
  cifs: update smb2_calc_size to use smb2_sync_hdr instead of smb2_hdr
  cifs: remove struct smb2_oplock_break_rsp
  cifs: remove rfc1002 header from all SMB2 response structures
  smb3: on reconnect set PreviousSessionId field
  smb3: Add posix create context for smb3.11 posix mounts
  smb3: add tracepoints for smb2/smb3 open
  cifs: add debug output to show nocase mount option
  smb3: add define for id for posix create context and corresponding struct
  cifs: update smb2_check_message to handle PDUs without a 4 byte length header
  smb3: allow "posix" mount option to enable new SMB311 protocol extensions
  smb3: add support for posix negotiate context
  cifs: allow disabling less secure legacy dialects
  ...

Pull gfs2 updates from Bob Peterson:
 "We've got nine more patches for this merge window.

   - remove sd_jheightsize to greatly simplify some code (Andreas
     Gruenbacher)

   - fix some comments (Andreas)

   - fix a glock recursion bug when allocation errors occur (Andreas)

   - improve the hole_size function so it returns the entire hole rather
     than figuring it out piecemeal (Andreas)

   - clean up gfs2_stuffed_write_end to remove a lot of redundancy
     (Andreas)

   - clarify code with regard to the way ordered writes are processed
     (Andreas)

   - a bunch of improvements and cleanups of the iomap code to pave the
     way for iomap writes, which is a future patch set (Andreas)

   - fix a bug where block reservations can run off the end of a bitmap
     (Bob Peterson)

   - add Andreas to the MAINTAINERS file (Bob Peterson)"

* tag 'gfs2-4.18.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2:
  MAINTAINERS: Add Andreas Gruenbacher as a maintainer for gfs2
  gfs2: Iomap cleanups and improvements
  gfs2: Remove ordered write mode handling from gfs2_trans_add_data
  gfs2: gfs2_stuffed_write_end cleanup
  gfs2: hole_size improvement
  GFS2: gfs2_free_extlen can return an extent that is too long
  GFS2: Fix allocation error bug with recursive rgrp glocking
  gfs2: Update find_metapath comment
  gfs2: Remove sdp->sd_jheightsize

Pull dlm updates from David Teigland:
 "These three commits fix and clean up the flags dlm was using on its
  SCTP sockets. This improves performance and fixes some bad connection
  delays"

* tag 'dlm-4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/teigland/linux-dlm:
  dlm: remove O_NONBLOCK flag in sctp_connect_to_sock
  dlm: make sctp_connect_to_sock() return in specified time
  dlm: fix a clerical error when set SCTP_NODELAY

Pull btrfs updates from David Sterba:
 "User visible features:

   - added support for the ioctl FS_IOC_FSGETXATTR, per-inode flags,
     successor of GET/SETFLAGS; now supports only existing flags:
     append, immutable, noatime, nodump, sync

   - 3 new unprivileged ioctls to allow users to enumerate subvolumes

   - dedupe syscall implementation does not restrict the range to 16MiB,
     though it still splits the whole range to 16MiB chunks

   - on user demand, rmdir() is able to delete an empty subvolume,
     export the capability in sysfs

   - fix inode number types in tracepoints, other cleanups

   - send: improved speed when dealing with a large removed directory,
     measurements show decrease from 2000 minutes to 2 minutes on a
     directory with 2 million entries

   - pre-commit check of superblock to detect a mysterious in-memory
     corruption

   - log message updates

  Other changes:

   - orphan inode cleanup improved, does no keep long-standing
     reservations that could lead up to early ENOSPC in some cases

   - slight improvement of handling snapshotted NOCOW files by avoiding
     some unnecessary tree searches

   - avoid OOM when dealing with many unmergeable small extents at flush
     time

   - speedup conversion of free space tree representations from/to
     bitmap/tree

   - code refactoring, deletion, cleanups:
      + delayed refs
      + delayed iput
      + redundant argument removals
      + memory barrier cleanups
      + remove a redundant mutex supposedly excluding several ioctls to
        run in parallel

   - new tracepoints for blockgroup manipulation

   - more sanity checks of compressed headers"

* tag 'for-4.18-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (183 commits)
  btrfs: Add unprivileged version of ino_lookup ioctl
  btrfs: Add unprivileged ioctl which returns subvolume's ROOT_REF
  btrfs: Add unprivileged ioctl which returns subvolume information
  Btrfs: clean up error handling in btrfs_truncate()
  btrfs: Factor out write portion of btrfs_get_blocks_direct
  btrfs: Factor out read portion of btrfs_get_blocks_direct
  btrfs: return ENOMEM if path allocation fails in btrfs_cross_ref_exist
  btrfs: raid56: Remove VLA usage
  btrfs: return error value if create_io_em failed in cow_file_range
  btrfs: drop useless member qgroup_reserved of btrfs_pending_snapshot
  btrfs: drop unused parameter qgroup_reserved
  btrfs: balance dirty metadata pages in btrfs_finish_ordered_io
  btrfs: lift some btrfs_cross_ref_exist checks in nocow path
  btrfs: Remove fs_info argument from btrfs_uuid_tree_rem
  btrfs: Remove fs_info argument from btrfs_uuid_tree_add
  Btrfs: remove unused check of skip_locking
  Btrfs: remove always true check in unlock_up
  Btrfs: grab write lock directly if write_lock_level is the max level
  Btrfs: move get root out of btrfs_search_slot to a helper
  Btrfs: use more straightforward extent_buffer_uptodate check
  ...

Pull affs fix from David Sterba:
 "A potential memory leak fix for AFFS"

* tag 'affs-for-4.18-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  affs: fix potential memory leak when parsing option 'prefix'

Pull aio updates from Al Viro:
 "Majority of AIO stuff this cycle. aio-fsync and aio-poll, mostly.

  The only thing I'm holding back for a day or so is Adam's aio ioprio -
  his last-minute fixup is trivial (missing stub in !CONFIG_BLOCK case),
  but let it sit in -next for decency sake..."

* 'work.aio-1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (46 commits)
  aio: sanitize the limit checking in io_submit(2)
  aio: fold do_io_submit() into callers
  aio: shift copyin of iocb into io_submit_one()
  aio_read_events_ring(): make a bit more readable
  aio: all callers of aio_{read,write,fsync,poll} treat 0 and -EIOCBQUEUED the same way
  aio: take list removal to (some) callers of aio_complete()
  aio: add missing break for the IOCB_CMD_FDSYNC case
  random: convert to ->poll_mask
  timerfd: convert to ->poll_mask
  eventfd: switch to ->poll_mask
  pipe: convert to ->poll_mask
  crypto: af_alg: convert to ->poll_mask
  net/rxrpc: convert to ->poll_mask
  net/iucv: convert to ->poll_mask
  net/phonet: convert to ->poll_mask
  net/nfc: convert to ->poll_mask
  net/caif: convert to ->poll_mask
  net/bluetooth: convert to ->poll_mask
  net/sctp: convert to ->poll_mask
  net/tipc: convert to ->poll_mask
  ...

Pull dcache lookup cleanups from Al Viro:
 "Cleaning ->lookup() instances up - mostly d_splice_alias() conversions"

* 'work.lookup' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (29 commits)
  switch the rest of procfs lookups to d_splice_alias()
  procfs: switch instantiate_t to d_splice_alias()
  don't bother with tid_fd_revalidate() in lookups
  proc_lookupfd_common(): don't bother with instantiate unless the file is open
  procfs: get rid of ancient BS in pid_revalidate() uses
  cifs_lookup(): switch to d_splice_alias()
  cifs_lookup(): cifs_get_inode_...() never returns 0 with *inode left NULL
  9p: unify paths in v9fs_vfs_lookup()
  ncp_lookup(): use d_splice_alias()
  hfsplus: switch to d_splice_alias()
  hfs: don't allow mounting over .../rsrc
  hfs: use d_splice_alias()
  omfs_lookup(): report IO errors, use d_splice_alias()
  orangefs_lookup: simplify
  openpromfs: switch to d_splice_alias()
  xfs_vn_lookup: simplify a bit
  adfs_lookup: do not fail with ENOENT on negatives, use d_splice_alias()
  adfs_lookup_byname: .. *is* taken care of in fs/namei.c
  romfs_lookup: switch to d_splice_alias()
  qnx6_lookup: switch to d_splice_alias()
  ...

Pull fasync fix from Jeff Layton:
 "Just a single fix for a deadlock in the fasync handling code that
  Kirill observed while testing.

  The fix is to change the fa_lock to be rwlock_t, and use a read lock
  in kill_fasync_rcu"

* tag 'locks-v4.18-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
  fasync: Fix deadlock between task-context and interrupt-context kill_fasync()

Pull documentation updates from Jonathan Corbet:
 "There's been a fair amount of work in the docs tree this time around,
  including:

   - Extensive RST conversions and organizational work in the
     memory-management docs thanks to Mike Rapoport.

   - An update of Documentation/features from Andrea Parri and a script
     to keep it updated.

   - Various LICENSES updates from Thomas, along with a script to check
     SPDX tags.

   - Work to fix dangling references to documentation files; this
     involved a fair number of one-liner comment changes outside of
     Documentation/

  ... and the usual list of documentation improvements, typo fixes, etc"

* tag 'docs-4.18' of git://git.lwn.net/linux: (103 commits)
  Documentation: document hung_task_panic kernel parameter
  docs/admin-guide/mm: add high level concepts overview
  docs/vm: move ksm and transhuge from "user" to "internals" section.
  docs: Use the kerneldoc comments for memalloc_no*()
  doc: document scope NOFS, NOIO APIs
  docs: update kernel versions and dates in tables
  docs/vm: transhuge: split userspace bits to admin-guide/mm/transhuge
  docs/vm: transhuge: minor updates
  docs/vm: transhuge: change sections order
  Documentation: arm: clean up Marvell Berlin family info
  Documentation: gpio: driver: Fix a typo and some odd grammar
  docs: ranoops.rst: fix location of ramoops.txt
  scripts/documentation-file-ref-check: rewrite it in perl with auto-fix mode
  docs: uio-howto.rst: use a code block to solve a warning
  mm, THP, doc: Add document for thp_swpout/thp_swpout_fallback
  w1: w1_io.c: fix a kernel-doc warning
  Documentation/process/posting: wrap text at 80 cols
  docs: admin-guide: add cgroup-v2 documentation
  Revert "Documentation/features/vm: Remove arch support status file for 'pte_special'"
  Documentation: refcount-vs-atomic: Update reference to LKMM doc.
  ...

We already earlier discouraged people from using this interface in
commit 88796e7e ("sched/swait: Document it clearly that the swait
facilities are special and shouldn't be used"), but I just got a pull
request with a new broken user.

So make the comment *really* clear.

The swait interfaces are bad, and should not be used unless you have
some *very* strong reasons that include tons of hard performance numbers
on just why you want to use them, and you show that you actually
understand that they aren't at all like the normal wait/wakeup
interfaces.

So far, every single user has been suspect.  The main user is KVM, which
is completely pointless (there is only ever one waiter, which avoids the
interface subtleties, but also means that having a queue instead of a
pointer is counter-productive and certainly not an "optimization").

So make the comments much stronger.

Not that anybody likely reads them anyway, but there's always some
slight hope that it will cause somebody to think twice.

I'd like to remove this interface entirely, but there is the theoretical
possibility that it's actually the right thing to use in some situation,
most likely some deep RT use.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Pull regmap updates from Mark Brown:
 "This is another quiet release for regmap, there's one minor feature
  improvement for the recently added slimbus support and a few minor
  fixes and cleanups"

* tag 'regmap-v4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap:
  regmap: slimbus: allow register offsets up to 16 bits
  regmap: add missing prototype for devm_init_slimbus
  regmap: Skip clk_put for attached clocks when freeing context
  regmap: include <linux/ktime.h> from include/linux/regmap.h

Pull spi updates from Mark Brown:
 "Quite a busy release for SPI, mainly as a result of Boris Brezillon's
  work on improving the integration with MTD for accelerated SPI flash
  controllers. He's added a new spi_mem interface which works a lot
  better with general hardware and converted the users over to it, as a
  result of this work we've got some MTD changes in here as well.

  Other highlights include:

   - Lots of spring cleaning for the s3c64xx driver.

   - Removal of the bcm53xx, the hardware is also supported by the mspi
     driver but SoC naming had caused people to miss the duplication.

   - Conversion of the pxa2xx driver to use the standard message
     processing loop rather than open coding.

   - A bunch of improvements to the runtime PM of the OMAP McSPI driver"

* tag 'spi-v4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi: (47 commits)
  spi: Fix typo on SPI_MEM help text
  spi: sh-msiof: Fix setting SIRMDR1.SYNCAC to match SITMDR1.SYNCAC
  mtd: devices: m25p80: Use spi_mem_set_drvdata() instead of spi_set_drvdata()
  spi: omap2-mcspi: Remove unnecessary pm_runtime_force_suspend()
  spi: Add missing pm_runtime_put_noidle() after failed get
  spi: ti-qspi: Make sure res_mmap != NULL before dereferencing it
  spi: spi-s3c64xx: Fix system resume support
  spi: bcm-qspi: Fix build failure caused by spi_flash_read() API removal
  spi: Get rid of the spi_flash_read() API
  mtd: spi-nor: Use the spi_mem_xx() API
  spi: ti-qspi: Implement the spi_mem interface
  spi: bcm-qspi: Implement the spi_mem interface
  spi: Make support for regular transfers optional when ->mem_ops != NULL
  spi: Extend the core to ease integration of SPI memory controllers
  spi: remove forgotten CONFIG_SPI_BCM53XX
  spi: remove the older/duplicated bcm53xx driver
  spi: pxa2xx: check clk_prepare_enable() return value
  spi: lpspi: Switch to SPDX identifier
  spi: mxs: Switch to SPDX identifier
  spi: imx: Switch to SPDX identifier
  ...

Merge tag 'chrome-platform-for-linus-4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/bleung/chrome-platform

Pull chrome platform updates from Benson Leung:

 - further changes from Dmitry related to the removal of platform data
   from atmel_mxt_ts and chromeos_laptop.

   This time, we have some changes that teach chromeos_laptop how to
   supply acpi properties for some input devices so that the peripheral
   driver doesn't have to do dmi matching on some Chromebook platforms.

 - new Chromebook Tablet switch driver, which is useful for x86
   convertible Chromebooks.

 - other misc cleanup

* tag 'chrome-platform-for-linus-4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/bleung/chrome-platform:
  platform/chrome: Use to_cros_ec_dev more broadly
  platform/chrome: chromeos_laptop: fix touchpad button mapping on Celes
  platform: chrome: Add input dependency for tablet switch driver
  platform/chrome: chromeos_laptop - supply properties for ACPI devices
  platform/chrome: chromeos_tbmc - add SPDX identifier
  platform: chrome: Add Tablet Switch ACPI driver
  platform/chrome: cros_ec_lpc: do not try DMI match when ACPI device found

Merge tag 'hwmon-for-linus-v4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging

Pull hwmon updates from Guenter Roeck:

 - asus_atk0110 driver modified to use new API

 - k10temp supports new CPUs and reports both Tctl and Tdie

 - minor fixes in gpio-fan, ltc2990, fschmd, and mc13783 drivers

* tag 'hwmon-for-linus-v4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging:
  hwmon: (asus_atk0110) Make use of device managed memory
  hwmon: (asus_atk0110) Replace deprecated device register call
  hwmon: (k10temp) Make function get_raw_temp static
  hwmon: (gpio-fan) Fix "#cooling-cells" property name in bindings
  MAINTAINERS: hwmon: Add Documentation/devicetree/bindings/hwmon
  hwmon: (ltc2990) support all measurement modes
  hwmon: (ltc2990) add devicetree binding
  hwmon: (ltc2990) Fix incorrect conversion of negative temperatures
  hwmon: (core) check parent dev != NULL when chip != NULL
  hwmon: (fschmd) fix typo 'can by' to 'can be'
  hwmon: (k10temp) Display both Tctl and Tdie
  hwmon: (k10temp) Add support for Stoney Ridge and Bristol Ridge CPUs
  hwmon: MC13783: Add uid and die temperature sensor inputs

Pull dma-mapping updates from Christoph Hellwig:

 - replace the force_dma flag with a dma_configure bus method. (Nipun
   Gupta, although one patch is іncorrectly attributed to me due to a
   git rebase bug)

 - use GFP_DMA32 more agressively in dma-direct. (Takashi Iwai)

 - remove PCI_DMA_BUS_IS_PHYS and rely on the dma-mapping API to do the
   right thing for bounce buffering.

 - move dma-debug initialization to common code, and apply a few
   cleanups to the dma-debug code.

 - cleanup the Kconfig mess around swiotlb selection

 - swiotlb comment fixup (Yisheng Xie)

 - a trivial swiotlb fix. (Dan Carpenter)

 - support swiotlb on RISC-V. (based on a patch from Palmer Dabbelt)

 - add a new generic dma-noncoherent dma_map_ops implementation and use
   it for arc, c6x and nds32.

 - improve scatterlist validity checking in dma-debug. (Robin Murphy)

 - add a struct device quirk to limit the dma-mask to 32-bit due to
   bridge/system issues, and switch x86 to use it instead of a local
   hack for VIA bridges.

 - handle devices without a dma_mask more gracefully in the dma-direct
   code.

* tag 'dma-mapping-4.18' of git://git.infradead.org/users/hch/dma-mapping: (48 commits)
  dma-direct: don't crash on device without dma_mask
  nds32: use generic dma_noncoherent_ops
  nds32: implement the unmap_sg DMA operation
  nds32: consolidate DMA cache maintainance routines
  x86/pci-dma: switch the VIA 32-bit DMA quirk to use the struct device flag
  x86/pci-dma: remove the explicit nodac and allowdac option
  x86/pci-dma: remove the experimental forcesac boot option
  Documentation/x86: remove a stray reference to pci-nommu.c
  core, dma-direct: add a flag 32-bit dma limits
  dma-mapping: remove unused gfp_t parameter to arch_dma_alloc_attrs
  dma-debug: check scatterlist segments
  c6x: use generic dma_noncoherent_ops
  arc: use generic dma_noncoherent_ops
  arc: fix arc_dma_{map,unmap}_page
  arc: fix arc_dma_sync_sg_for_{cpu,device}
  arc: simplify arc_dma_sync_single_for_{cpu,device}
  dma-mapping: provide a generic dma-noncoherent implementation
  dma-mapping: simplify Kconfig dependencies
  riscv: add swiotlb support
  riscv: only enable ZONE_DMA32 for 64-bit
  ...

Pull misc vfs updates from Al Viro:
 "Misc bits and pieces not fitting into anything more specific"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  vfs: delete unnecessary assignment in vfs_listxattr
  Documentation: filesystems: update filesystem locking documentation
  vfs: namei: use path_equal() in follow_dotdot()
  fs.h: fix outdated comment about file flags
  __inode_security_revalidate() never gets NULL opt_dentry
  make xattr_getsecurity() static
  vfat: simplify checks in vfat_lookup()
  get rid of dead code in d_find_alias()
  it's SB_BORN, not MS_BORN...
  msdos_rmdir(): kill BS comment
  remove rpc_rmdir()
  fs: avoid fdput() after failed fdget() in vfs_dedupe_file_range()

Pull procfs updates from Al Viro:
 "Christoph's proc_create_... cleanups series"

* 'hch.procfs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (44 commits)
  xfs, proc: hide unused xfs procfs helpers
  isdn/gigaset: add back gigaset_procinfo assignment
  proc: update SIZEOF_PDE_INLINE_NAME for the new pde fields
  tty: replace ->proc_fops with ->proc_show
  ide: replace ->proc_fops with ->proc_show
  ide: remove ide_driver_proc_write
  isdn: replace ->proc_fops with ->proc_show
  atm: switch to proc_create_seq_private
  atm: simplify procfs code
  bluetooth: switch to proc_create_seq_data
  netfilter/x_tables: switch to proc_create_seq_private
  netfilter/xt_hashlimit: switch to proc_create_{seq,single}_data
  neigh: switch to proc_create_seq_data
  hostap: switch to proc_create_{seq,single}_data
  bonding: switch to proc_create_seq_data
  rtc/proc: switch to proc_create_single_data
  drbd: switch to proc_create_single
  resource: switch to proc_create_seq_data
  staging/rtl8192u: simplify procfs code
  jfs: simplify procfs code
  ...