linux.git/kernel/Kconfig.locks, branch v5.2-rc1

Merge tag 'arm64-mmiowb' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

2019-05-06T23:57:52+00:00

Pull mmiowb removal from Will Deacon:
 "Remove Mysterious Macro Intended to Obscure Weird Behaviours (mmiowb())

  Remove mmiowb() from the kernel memory barrier API and instead, for
  architectures that need it, hide the barrier inside spin_unlock() when
  MMIO has been performed inside the critical section.

  The only relatively recent changes have been addressing review
  comments on the documentation, which is in a much better shape thanks
  to the efforts of Ben and Ingo.

  I was initially planning to split this into two pull requests so that
  you could run the coccinelle script yourself, however it's been plain
  sailing in linux-next so I've just included the whole lot here to keep
  things simple"

* tag 'arm64-mmiowb' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (23 commits)
  docs/memory-barriers.txt: Update I/O section to be clearer about CPU vs thread
  docs/memory-barriers.txt: Fix style, spacing and grammar in I/O section
  arch: Remove dummy mmiowb() definitions from arch code
  net/ethernet/silan/sc92031: Remove stale comment about mmiowb()
  i40iw: Redefine i40iw_mmiowb() to do nothing
  scsi/qla1280: Remove stale comment about mmiowb()
  drivers: Remove explicit invocations of mmiowb()
  drivers: Remove useless trailing comments from mmiowb() invocations
  Documentation: Kill all references to mmiowb()
  riscv/mmiowb: Hook up mmwiob() implementation to asm-generic code
  powerpc/mmiowb: Hook up mmwiob() implementation to asm-generic code
  ia64/mmiowb: Add unconditional mmiowb() to arch_spin_unlock()
  mips/mmiowb: Add unconditional mmiowb() to arch_spin_unlock()
  sh/mmiowb: Add unconditional mmiowb() to arch_spin_unlock()
  m68k/io: Remove useless definition of mmiowb()
  nds32/io: Remove useless definition of mmiowb()
  x86/io: Remove useless definition of mmiowb()
  arm64/io: Remove useless definition of mmiowb()
  ARM/io: Remove useless definition of mmiowb()
  mmiowb: Hook up mmiowb helpers to spinlocks and generic I/O accessors
  ...

asm-generic/mmiowb: Add generic implementation of mmiowb() tracking

2019-04-08T10:59:39+00:00

In preparation for removing all explicit mmiowb() calls from driver
code, implement a tracking system in asm-generic based loosely on the
PowerPC implementation. This allows architectures with a non-empty
mmiowb() definition to have the barrier automatically inserted in
spin_unlock() following a critical section containing an I/O write.

Acked-by: Linus Torvalds 
Signed-off-by: Will Deacon

locking/rwsem: Remove rwsem-spinlock.c & use rwsem-xadd.c for all archs

2019-04-03T12:50:52+00:00

Currently, we have two different implementation of rwsem:

 1) CONFIG_RWSEM_GENERIC_SPINLOCK (rwsem-spinlock.c)
 2) CONFIG_RWSEM_XCHGADD_ALGORITHM (rwsem-xadd.c)

As we are going to use a single generic implementation for rwsem-xadd.c
and no architecture-specific code will be needed, there is no point
in keeping two different implementations of rwsem. In most cases, the
performance of rwsem-spinlock.c will be worse. It also doesn't get all
the performance tuning and optimizations that had been implemented in
rwsem-xadd.c over the years.

For simplication, we are going to remove rwsem-spinlock.c and make all
architectures use a single implementation of rwsem - rwsem-xadd.c.

All references to RWSEM_GENERIC_SPINLOCK and RWSEM_XCHGADD_ALGORITHM
in the code are removed.

Suggested-by: Peter Zijlstra 
Signed-off-by: Waiman Long 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Linus Torvalds 
Cc: Andrew Morton 
Cc: Arnd Bergmann 
Cc: Borislav Petkov 
Cc: Davidlohr Bueso 
Cc: H. Peter Anvin 
Cc: Paul E. McKenney 
Cc: Thomas Gleixner 
Cc: Tim Chen 
Cc: Will Deacon 
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: linux-m68k@lists.linux-m68k.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-um@lists.infradead.org
Cc: linux-xtensa@linux-xtensa.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: nios2-dev@lists.rocketboards.org
Cc: openrisc@lists.librecores.org
Cc: uclinux-h8-devel@lists.sourceforge.jp
Link: https://lkml.kernel.org/r/20190322143008.21313-3-longman@redhat.com
Signed-off-by: Ingo Molnar

bpf: introduce bpf_spin_lock

2019-02-01T19:55:38+00:00

Introduce 'struct bpf_spin_lock' and bpf_spin_lock/unlock() helpers to let
bpf program serialize access to other variables.

Example:
struct hash_elem {
    int cnt;
    struct bpf_spin_lock lock;
};
struct hash_elem * val = bpf_map_lookup_elem(&hash_map, &key);
if (val) {
    bpf_spin_lock(&val->lock);
    val->cnt++;
    bpf_spin_unlock(&val->lock);
}

Restrictions and safety checks:
- bpf_spin_lock is only allowed inside HASH and ARRAY maps.
- BTF description of the map is mandatory for safety analysis.
- bpf program can take one bpf_spin_lock at a time, since two or more can
  cause dead locks.
- only one 'struct bpf_spin_lock' is allowed per map element.
  It drastically simplifies implementation yet allows bpf program to use
  any number of bpf_spin_locks.
- when bpf_spin_lock is taken the calls (either bpf2bpf or helpers) are not allowed.
- bpf program must bpf_spin_unlock() before return.
- bpf program can access 'struct bpf_spin_lock' only via
  bpf_spin_lock()/bpf_spin_unlock() helpers.
- load/store into 'struct bpf_spin_lock lock;' field is not allowed.
- to use bpf_spin_lock() helper the BTF description of map value must be
  a struct and have 'struct bpf_spin_lock anyname;' field at the top level.
  Nested lock inside another struct is not allowed.
- syscall map_lookup doesn't copy bpf_spin_lock field to user space.
- syscall map_update and program map_update do not update bpf_spin_lock field.
- bpf_spin_lock cannot be on the stack or inside networking packet.
  bpf_spin_lock can only be inside HASH or ARRAY map value.
- bpf_spin_lock is available to root only and to all program types.
- bpf_spin_lock is not allowed in inner maps of map-in-map.
- ld_abs is not allowed inside spin_lock-ed region.
- tracing progs and socket filter progs cannot use bpf_spin_lock due to
  insufficient preemption checks

Implementation details:
- cgroup-bpf class of programs can nest with xdp/tc programs.
  Hence bpf_spin_lock is equivalent to spin_lock_irqsave.
  Other solutions to avoid nested bpf_spin_lock are possible.
  Like making sure that all networking progs run with softirq disabled.
  spin_lock_irqsave is the simplest and doesn't add overhead to the
  programs that don't use it.
- arch_spinlock_t is used when its implemented as queued_spin_lock
- archs can force their own arch_spinlock_t
- on architectures where queued_spin_lock is not available and
  sizeof(arch_spinlock_t) != sizeof(__u32) trivial lock is used.
- presence of bpf_spin_lock inside map value could have been indicated via
  extra flag during map_create, but specifying it via BTF is cleaner.
  It provides introspection for map key/value and reduces user mistakes.

Next steps:
- allow bpf_spin_lock in other map types (like cgroup local storage)
- introduce BPF_F_LOCK flag for bpf_map_update() syscall and helper
  to request kernel to grab bpf_spin_lock before rewriting the value.
  That will serialize access to map elements.

Acked-by: Peter Zijlstra (Intel) 
Signed-off-by: Alexei Starovoitov 
Signed-off-by: Daniel Borkmann

locking/mutex: Allow MUTEX_SPIN_ON_OWNER when DEBUG_MUTEXES

2016-10-25T09:31:51+00:00

Now that mutex::count and mutex::owner are the same field, we can
allow SPIN_ON_OWNER while DEBUG_MUTEX.

Tested-by: Jason Low 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

locking/qrwlock: Rename QUEUE_RWLOCK to QUEUED_RWLOCKS

2015-05-12T07:46:00+00:00

To be consistent with the queued spinlocks which use
CONFIG_QUEUED_SPINLOCKS config parameter, the one for the queued
rwlocks is now renamed to CONFIG_QUEUED_RWLOCKS.

Signed-off-by: Waiman Long 
Cc: Borislav Petkov 
Cc: Douglas Hatch 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Scott J Norton 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1431367031-36697-1-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar

locking/pvqspinlock: Rename QUEUED_SPINLOCK to QUEUED_SPINLOCKS

2015-05-11T07:52:09+00:00

Valentin Rothberg reported that we use CONFIG_QUEUED_SPINLOCKS
in arch/x86/kernel/paravirt_patch_32.c, while the symbol is
called CONFIG_QUEUED_SPINLOCK. (Note the extra 'S')

But the typo was natural: the proper English term for such
a generic object would be 'queued spinlocks' - so rename
this and related symbols accordingly to the plural form.

Reported-by: Valentin Rothberg 
Cc: Douglas Hatch 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Scott J Norton 
Cc: Thomas Gleixner 
Cc: Waiman Long 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

locking/pvqspinlock, x86: Enable PV qspinlock for Xen

2015-05-08T10:37:18+00:00

This patch adds the necessary Xen specific code to allow Xen to
support the CPU halting and kicking operations needed by the queue
spinlock PV code.

Signed-off-by: David Vrabel 
Signed-off-by: Waiman Long 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Andrew Morton 
Cc: Boris Ostrovsky 
Cc: Borislav Petkov 
Cc: Daniel J Blueman 
Cc: Douglas Hatch 
Cc: H. Peter Anvin 
Cc: Konrad Rzeszutek Wilk 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Paolo Bonzini 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Raghavendra K T 
Cc: Rik van Riel 
Cc: Scott J Norton 
Cc: Thomas Gleixner 
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-12-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar

locking/pvqspinlock, x86: Enable PV qspinlock for KVM

2015-05-08T10:37:17+00:00

This patch adds the necessary KVM specific code to allow KVM to
support the CPU halting and kicking operations needed by the queue
spinlock PV code.

Signed-off-by: Waiman Long 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Andrew Morton 
Cc: Boris Ostrovsky 
Cc: Borislav Petkov 
Cc: Daniel J Blueman 
Cc: David Vrabel 
Cc: Douglas Hatch 
Cc: H. Peter Anvin 
Cc: Konrad Rzeszutek Wilk 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Paolo Bonzini 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Raghavendra K T 
Cc: Rik van Riel 
Cc: Scott J Norton 
Cc: Thomas Gleixner 
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-11-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar

locking/qspinlock: Introduce a simple generic 4-byte queued spinlock

2015-05-08T10:36:25+00:00

This patch introduces a new generic queued spinlock implementation that
can serve as an alternative to the default ticket spinlock. Compared
with the ticket spinlock, this queued spinlock should be almost as fair
as the ticket spinlock. It has about the same speed in single-thread
and it can be much faster in high contention situations especially when
the spinlock is embedded within the data structure to be protected.

Only in light to moderate contention where the average queue depth
is around 1-3 will this queued spinlock be potentially a bit slower
due to the higher slowpath overhead.

This queued spinlock is especially suit to NUMA machines with a large
number of cores as the chance of spinlock contention is much higher
in those machines. The cost of contention is also higher because of
slower inter-node memory traffic.

Due to the fact that spinlocks are acquired with preemption disabled,
the process will not be migrated to another CPU while it is trying
to get a spinlock. Ignoring interrupt handling, a CPU can only be
contending in one spinlock at any one time. Counting soft IRQ, hard
IRQ and NMI, a CPU can only have a maximum of 4 concurrent lock waiting
activities.  By allocating a set of per-cpu queue nodes and used them
to form a waiting queue, we can encode the queue node address into a
much smaller 24-bit size (including CPU number and queue node index)
leaving one byte for the lock.

Please note that the queue node is only needed when waiting for the
lock. Once the lock is acquired, the queue node can be released to
be used later.

Signed-off-by: Waiman Long 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Andrew Morton 
Cc: Boris Ostrovsky 
Cc: Borislav Petkov 
Cc: Daniel J Blueman 
Cc: David Vrabel 
Cc: Douglas Hatch 
Cc: H. Peter Anvin 
Cc: Konrad Rzeszutek Wilk 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Paolo Bonzini 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Raghavendra K T 
Cc: Rik van Riel 
Cc: Scott J Norton 
Cc: Thomas Gleixner 
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-2-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar