linux-toradex.git/kernel/Kconfig.locks, branch v4.13-rc7

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

locking/mcs: Better differentiate between MCS variants

2015-01-14T14:07:32+00:00

We have two flavors of the MCS spinlock: standard and cancelable (OSQ).
While each one is independent of the other, we currently mix and match
them. This patch:

  - Moves the OSQ code out of mcs_spinlock.h (which only deals with the traditional
    version) into include/linux/osq_lock.h. No unnecessary code is added to the
    more global header file, anything locks that make use of OSQ must include
    it anyway.

  - Renames mcs_spinlock.c to osq_lock.c. This file only contains osq code.

  - Introduces a CONFIG_LOCK_SPIN_ON_OWNER in order to only build osq_lock
    if there is support for it.

Signed-off-by: Davidlohr Bueso 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Thomas Gleixner 
Cc: "Paul E. McKenney" 
Cc: Jason Low 
Cc: Linus Torvalds 
Cc: Mikulas Patocka 
Cc: Waiman Long 
Link: http://lkml.kernel.org/r/1420573509-24774-5-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar

locking/rwsem: Add CONFIG_RWSEM_SPIN_ON_OWNER

2014-07-16T12:57:13+00:00

Just like with mutexes (CONFIG_MUTEX_SPIN_ON_OWNER),
encapsulate the dependencies for rwsem optimistic spinning.
No logical changes here as it continues to depend on both
SMP and the XADD algorithm variant.

Signed-off-by: Davidlohr Bueso 
Acked-by: Jason Low 
[ Also make it depend on ARCH_SUPPORTS_ATOMIC_RMW. ]
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1405112406-13052-2-git-send-email-davidlohr@hp.com
Cc: aswin@hp.com
Cc: Chris Mason 
Cc: Davidlohr Bueso 
Cc: Josef Bacik 
Cc: Linus Torvalds 
Cc: Waiman Long 
Signed-off-by: Ingo Molnar 

Signed-off-by: Ingo Molnar

locking/mutex: Disable optimistic spinning on some architectures

2014-07-16T12:57:07+00:00

The optimistic spin code assumes regular stores and cmpxchg() play nice;
this is found to not be true for at least: parisc, sparc32, tile32,
metag-lock1, arc-!llsc and hexagon.

There is further wreckage, but this in particular seemed easy to
trigger, so blacklist this.

Opt in for known good archs.

Signed-off-by: Peter Zijlstra 
Reported-by: Mikulas Patocka 
Cc: David Miller 
Cc: Chris Metcalf 
Cc: James Bottomley 
Cc: Vineet Gupta 
Cc: Jason Low 
Cc: Waiman Long 
Cc: "James E.J. Bottomley" 
Cc: Paul McKenney 
Cc: John David Anglin 
Cc: James Hogan 
Cc: Linus Torvalds 
Cc: Davidlohr Bueso 
Cc: stable@vger.kernel.org
Cc: Benjamin Herrenschmidt 
Cc: Catalin Marinas 
Cc: Russell King 
Cc: Will Deacon 
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: sparclinux@vger.kernel.org
Link: http://lkml.kernel.org/r/20140606175316.GV13930@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar

locking/rwlocks: Introduce 'qrwlocks' - fair, queued rwlocks

2014-06-06T05:58:28+00:00

This rwlock uses the arch_spin_lock_t as a waitqueue, and assuming the
arch_spin_lock_t is a fair lock (ticket,mcs etc..) the resulting
rwlock is a fair lock.

It fits in the same 8 bytes as the regular rwlock_t by folding the
reader and writer count into a single integer, using the remaining 4
bytes for the arch_spinlock_t.

Architectures that can single-copy adress bytes can optimize
queue_write_unlock() with a 0 write to the LSB (the write count).

Performance as measured by Davidlohr Bueso (rwlock_t -> qrwlock_t):

 +--------------+-------------+---------------+
 |   Workload   |   #users    |     delta     |
 +--------------+-------------+---------------+
 | alltests     | > 1400      | -4.83%        |
 | custom       | 0-100,> 100 | +1.43%,-1.57% |
 | high_systime | > 1000      | -2.61         |
 | shared       | all         | +0.32         |
 +--------------+-------------+---------------+

http://www.stgolabs.net/qrwlock-stuff/aim7-results-vs-rwsem_optsin/

Signed-off-by: Waiman Long 
[peterz: near complete rewrite]
Signed-off-by: Peter Zijlstra 
Cc: Arnd Bergmann 
Cc: Linus Torvalds 
Cc: "Paul E.McKenney" 
Cc: linux-arch@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/n/tip-gac1nnl3wvs2ij87zv2xkdzq@git.kernel.org
Signed-off-by: Ingo Molnar