Pull TIF_NOTIFY_SIGNAL updates from Jens Axboe:
 "This sits on top of of the core entry/exit and x86 entry branch from
  the tip tree, which contains the generic and x86 parts of this work.

  Here we convert the rest of the archs to support TIF_NOTIFY_SIGNAL.

  With that done, we can get rid of JOBCTL_TASK_WORK from task_work and
  signal.c, and also remove a deadlock work-around in io_uring around
  knowing that signal based task_work waking is invoked with the sighand
  wait queue head lock.

  The motivation for this work is to decouple signal notify based
  task_work, of which io_uring is a heavy user of, from sighand. The
  sighand lock becomes a huge contention point, particularly for
  threaded workloads where it's shared between threads. Even outside of
  threaded applications it's slower than it needs to be.

  Roman Gershman <romger@amazon.com> reported that his networked
  workload dropped from 1.6M QPS at 80% CPU to 1.0M QPS at 100% CPU
  after io_uring was changed to use TIF_NOTIFY_SIGNAL. The time was all
  spent hammering on the sighand lock, showing 57% of the CPU time there
  [1].

  There are further cleanups possible on top of this. One example is
  TIF_PATCH_PENDING, where a patch already exists to use
  TIF_NOTIFY_SIGNAL instead. Hopefully this will also lead to more
  consolidation, but the work stands on its own as well"

[1] https://github.com/axboe/liburing/issues/215

* tag 'tif-task_work.arch-2020-12-14' of git://git.kernel.dk/linux-block: (28 commits)
  io_uring: remove 'twa_signal_ok' deadlock work-around
  kernel: remove checking for TIF_NOTIFY_SIGNAL
  signal: kill JOBCTL_TASK_WORK
  io_uring: JOBCTL_TASK_WORK is no longer used by task_work
  task_work: remove legacy TWA_SIGNAL path
  sparc: add support for TIF_NOTIFY_SIGNAL
  riscv: add support for TIF_NOTIFY_SIGNAL
  nds32: add support for TIF_NOTIFY_SIGNAL
  ia64: add support for TIF_NOTIFY_SIGNAL
  h8300: add support for TIF_NOTIFY_SIGNAL
  c6x: add support for TIF_NOTIFY_SIGNAL
  alpha: add support for TIF_NOTIFY_SIGNAL
  xtensa: add support for TIF_NOTIFY_SIGNAL
  arm: add support for TIF_NOTIFY_SIGNAL
  microblaze: add support for TIF_NOTIFY_SIGNAL
  hexagon: add support for TIF_NOTIFY_SIGNAL
  csky: add support for TIF_NOTIFY_SIGNAL
  openrisc: add support for TIF_NOTIFY_SIGNAL
  sh: add support for TIF_NOTIFY_SIGNAL
  um: add support for TIF_NOTIFY_SIGNAL
  ...

Pull regset updates from Al Viro:
 "Dead code removal, mostly.

  The only exception is a bit of cleanups on itanic (getting rid of
  redundant stack unwinds - each access_uarea() call does it and we call
  that 7 times in a row in ptrace_[sg]etregs(), *after* having done it
  ourselves in the caller; location where the user registers have been
  spilled won't change under us, and we can bloody well just call
  access_elf_reg() directly, giving it the unw_frame_info we'd
  calculated for our own purposes)"

* 'regset.followup' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  c6x: kill ELF_CORE_COPY_FPREGS
  whack-a-mole: USE_ELF_CORE_DUMP
  [ia64] ptrace_[sg]etregs(): use access_elf_reg() instead of access_uarea()
  [ia64] missed cleanups from switch to regset coredumps
  arm: kill dump_task_regs()

Wire up TIF_NOTIFY_SIGNAL handling for ia64.

Cc: linux-ia64@vger.kernel.org
[axboe: added fixes from Mike Rapoport <rppt@kernel.org>]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

We call arch_cpu_idle() with RCU disabled, but then use
local_irq_{en,dis}able(), which invokes tracing, which relies on RCU.

Switch all arch_cpu_idle() implementations to use
raw_local_irq_{en,dis}able() and carefully manage the
lockdep,rcu,tracing state like we do in entry.

(XXX: we really should change arch_cpu_idle() to not return with
interrupts enabled)

Reported-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lkml.kernel.org/r/20201120114925.594122626@infradead.org

a bunch of function could've been made static back in 2008 when
ia64 switched to regset-based coredumps

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

All the callers currently do this, clean it up and move the clearing
into tracehook_notify_resume() instead.

Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull kernel_clone() updates from Christian Brauner:
 "During the v5.9 merge window we reworked the process creation
  codepaths across multiple architectures. After this work we were only
  left with the _do_fork() helper based on the struct kernel_clone_args
  calling convention. As was pointed out _do_fork() isn't valid
  kernelese especially for a helper that isn't just static.

  This series removes the _do_fork() helper and introduces the new
  kernel_clone() helper. The process creation cleanup didn't change the
  name to something more reasonable mainly because _do_fork() was used
  in quite a few places. So sending this as a separate series seemed the
  better strategy.

  I originally intended to send this early in the v5.9 development cycle
  after the merge window had closed but given that this was touching
  quite a few places I decided to defer this until the v5.10 merge
  window"

* tag 'kernel-clone-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  sched: remove _do_fork()
  tracing: switch to kernel_clone()
  kgdbts: switch to kernel_clone()
  kprobes: switch to kernel_clone()
  x86: switch to kernel_clone()
  sparc: switch to kernel_clone()
  nios2: switch to kernel_clone()
  m68k: switch to kernel_clone()
  ia64: switch to kernel_clone()
  h8300: switch to kernel_clone()
  fork: introduce kernel_clone()

perfmon has been marked broken and thus been disabled for all builds
for more than two years.  Remove it entirely.

Cc: Anant Thazhemadam <anant.thazhemadam@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Enthusiastically-ACKed-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20200911094920.1173631-1-hch@lst.de

The old _do_fork() helper is removed in favor of the new kernel_clone() helper.
The latter adheres to naming conventions for kernel internal syscall helpers.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: linux-ia64@vger.kernel.org
Link: https://lore.kernel.org/r/20200819104655.436656-4-christian.brauner@ubuntu.com

Pull locking updates from Thomas Gleixner:
 "A set of locking fixes and updates:

   - Untangle the header spaghetti which causes build failures in
     various situations caused by the lockdep additions to seqcount to
     validate that the write side critical sections are non-preemptible.

   - The seqcount associated lock debug addons which were blocked by the
     above fallout.

     seqcount writers contrary to seqlock writers must be externally
     serialized, which usually happens via locking - except for strict
     per CPU seqcounts. As the lock is not part of the seqcount, lockdep
     cannot validate that the lock is held.

     This new debug mechanism adds the concept of associated locks.
     sequence count has now lock type variants and corresponding
     initializers which take a pointer to the associated lock used for
     writer serialization. If lockdep is enabled the pointer is stored
     and write_seqcount_begin() has a lockdep assertion to validate that
     the lock is held.

     Aside of the type and the initializer no other code changes are
     required at the seqcount usage sites. The rest of the seqcount API
     is unchanged and determines the type at compile time with the help
     of _Generic which is possible now that the minimal GCC version has
     been moved up.

     Adding this lockdep coverage unearthed a handful of seqcount bugs
     which have been addressed already independent of this.

     While generally useful this comes with a Trojan Horse twist: On RT
     kernels the write side critical section can become preemtible if
     the writers are serialized by an associated lock, which leads to
     the well known reader preempts writer livelock. RT prevents this by
     storing the associated lock pointer independent of lockdep in the
     seqcount and changing the reader side to block on the lock when a
     reader detects that a writer is in the write side critical section.

   - Conversion of seqcount usage sites to associated types and
     initializers"

* tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
  locking/seqlock, headers: Untangle the spaghetti monster
  locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header
  x86/headers: Remove APIC headers from <asm/smp.h>
  seqcount: More consistent seqprop names
  seqcount: Compress SEQCNT_LOCKNAME_ZERO()
  seqlock: Fold seqcount_LOCKNAME_init() definition
  seqlock: Fold seqcount_LOCKNAME_t definition
  seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g
  hrtimer: Use sequence counter with associated raw spinlock
  kvm/eventfd: Use sequence counter with associated spinlock
  userfaultfd: Use sequence counter with associated spinlock
  NFSv4: Use sequence counter with associated spinlock
  iocost: Use sequence counter with associated spinlock
  raid5: Use sequence counter with associated spinlock
  vfs: Use sequence counter with associated spinlock
  timekeeping: Use sequence counter with associated raw spinlock
  xfrm: policy: Use sequence counters with associated lock
  netfilter: nft_set_rbtree: Use sequence counter with associated rwlock
  netfilter: conntrack: Use sequence counter with associated spinlock
  sched: tasks: Use sequence counter with associated spinlock
  ...