linux-toradex.git/lib/lockref.c, branch v4.9-rc3

locking/lockref: Remove homebrew cmpxchg64_relaxed() macro definition

2015-08-12T09:59:04+00:00

cmpxchg64_relaxed() is now defined by linux/atomic.h, so we can
remove our local definition from the lockref code.

Signed-off-by: Will Deacon 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Waiman.Long@hp.com
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/1438880084-18856-5-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar

locking: Remove ACCESS_ONCE() usage

2015-02-24T07:44:16+00:00

With the new standardized functions, we can replace all
ACCESS_ONCE() calls across relevant locking - this includes
lockref and seqlock while at it.

ACCESS_ONCE() does not work reliably on non-scalar types.
For example gcc 4.6 and 4.7 might remove the volatile tag
for such accesses during the SRA (scalar replacement of
aggregates) step:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145

Update the new calls regardless of if it is a scalar type,
this is cleaner than having three alternatives.

Signed-off-by: Davidlohr Bueso 
Cc: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Cc: Thomas Gleixner 
Cc: Paul E. McKenney 
Link: http://lkml.kernel.org/r/1424662301.6539.18.camel@stgolabs.net
Signed-off-by: Ingo Molnar

dcache: let the dentry count go down to zero without taking d_lock

2015-01-26T04:16:29+00:00

We can be more aggressive about this, if we are clever and careful. This is subtle.

Signed-off-by: Linus Torvalds 
Signed-off-by: Al Viro

arch, locking: Ciao arch_mutex_cpu_relax()

2014-07-17T10:32:47+00:00

The arch_mutex_cpu_relax() function, introduced by 34b133f, is
hacky and ugly. It was added a few years ago to address the fact
that common cpu_relax() calls include yielding on s390, and thus
impact the optimistic spinning functionality of mutexes. Nowadays
we use this function well beyond mutexes: rwsem, qrwlock, mcs and
lockref. Since the macro that defines the call is in the mutex header,
any users must include mutex.h and the naming is misleading as well.

This patch (i) renames the call to cpu_relax_lowlatency  ("relax, but
only if you can do it with very low latency") and (ii) defines it in
each arch's asm/processor.h local header, just like for regular cpu_relax
functions. On all archs, except s390, cpu_relax_lowlatency is simply cpu_relax,
and thus we can take it out of mutex.h. While this can seem redundant,
I believe it is a good choice as it allows us to move out arch specific
logic from generic locking primitives and enables future(?) archs to
transparently define it, similarly to System Z.

Signed-off-by: Davidlohr Bueso 
Signed-off-by: Peter Zijlstra 
Cc: Andrew Morton 
Cc: Anton Blanchard 
Cc: Aurelien Jacquiot 
Cc: Benjamin Herrenschmidt 
Cc: Bharat Bhushan 
Cc: Catalin Marinas 
Cc: Chen Liqin 
Cc: Chris Metcalf 
Cc: Christian Borntraeger 
Cc: Chris Zankel 
Cc: David Howells 
Cc: David S. Miller 
Cc: Deepthi Dharwar 
Cc: Dominik Dingel 
Cc: Fenghua Yu 
Cc: Geert Uytterhoeven 
Cc: Guan Xuetao 
Cc: Haavard Skinnemoen 
Cc: Hans-Christian Egtvedt 
Cc: Heiko Carstens 
Cc: Helge Deller 
Cc: Hirokazu Takata 
Cc: Ivan Kokshaysky 
Cc: James E.J. Bottomley 
Cc: James Hogan 
Cc: Jason Wang 
Cc: Jesper Nilsson 
Cc: Joe Perches 
Cc: Jonas Bonn 
Cc: Joseph Myers 
Cc: Kees Cook 
Cc: Koichi Yasutake 
Cc: Lennox Wu 
Cc: Linus Torvalds 
Cc: Mark Salter 
Cc: Martin Schwidefsky 
Cc: Matt Turner 
Cc: Max Filippov 
Cc: Michael Neuling 
Cc: Michal Simek 
Cc: Mikael Starvik 
Cc: Nicolas Pitre 
Cc: Paolo Bonzini 
Cc: Paul Burton 
Cc: Paul E. McKenney 
Cc: Paul Gortmaker 
Cc: Paul Mackerras 
Cc: Qais Yousef 
Cc: Qiaowei Ren 
Cc: Rafael Wysocki 
Cc: Ralf Baechle 
Cc: Richard Henderson 
Cc: Richard Kuo 
Cc: Russell King 
Cc: Steven Miao 
Cc: Steven Rostedt 
Cc: Stratos Karafotis 
Cc: Tim Chen 
Cc: Tony Luck 
Cc: Vasily Kulikov 
Cc: Vineet Gupta 
Cc: Vineet Gupta 
Cc: Waiman Long 
Cc: Will Deacon 
Cc: Wolfram Sang 
Cc: adi-buildroot-devel@lists.sourceforge.net
Cc: linux390@de.ibm.com
Cc: linux-alpha@vger.kernel.org
Cc: linux-am33-list@redhat.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: linux-cris-kernel@axis.com
Cc: linux-hexagon@vger.kernel.org
Cc: linux-ia64@vger.kernel.org
Cc: linux@lists.openrisc.net
Cc: linux-m32r-ja@ml.linux-m32r.org
Cc: linux-m32r@ml.linux-m32r.org
Cc: linux-m68k@lists.linux-m68k.org
Cc: linux-metag@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: linux-xtensa@linux-xtensa.org
Cc: sparclinux@vger.kernel.org
Link: http://lkml.kernel.org/r/1404079773.2619.4.camel@buesod1.americas.hpqcorp.net
Signed-off-by: Ingo Molnar

lockref: include mutex.h rather than reinvent arch_mutex_cpu_relax

2013-11-28T04:37:33+00:00

arch_mutex_cpu_relax is already conditionally defined in mutex.h, so
simply include that header rather than replicate the code here.

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

lockref: use BLOATED_SPINLOCKS to avoid explicit config dependencies

2013-11-15T00:32:20+00:00

Avoid the fragile Kconfig construct guestimating spinlock_t sizes; use a
friendly compile-time test to determine this.

[kirill.shutemov@linux.intel.com: drop CONFIG_CMPXCHG_LOCKREF]
Signed-off-by: Peter Zijlstra 
Signed-off-by: Kirill A. Shutemov 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge tag 'gfs2-merge-window' of git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-3.0-nmw

2013-11-10T22:11:00+00:00

Pull gfs2 updates from Steven Whitehouse:
 "The main feature of interest this time is quota updates.  There are
  some clean ups and some patches to use the new generic lru list code.

  There is still plenty of scope for some further changes in due course -
  faster lookups of quota structures is very much on the todo list.
  Also, a start has been made towards the more tricky issue of using the
  generic lru code with glocks, but that will have to be completed in a
  subsequent merge window.

  The other, more minor feature, is that there have been a number of
  performance patches which relate to block allocation.  In particular
  they will improve performance when the disk is nearly full"

* tag 'gfs2-merge-window' of git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-3.0-nmw:
  GFS2: Use generic list_lru for quota
  GFS2: Rename quota qd_lru_lock qd_lock
  GFS2: Use reflink for quota data cache
  GFS2: Use lockref for glocks
  GFS2: Protect quota sync generation
  GFS2: Inline qd_trylock into gfs2_quota_unlock
  GFS2: Make two similar quota code fragments into a function
  GFS2: Remove obsolete quota tunable
  GFS2: Move gfs2_icbit_munge into quota.c
  GFS2: Speed up starting point selection for block allocation
  GFS2: Add allocation parameters structure
  GFS2: Clean up reservation removal
  GFS2: fix dentry leaks
  GFS2: new function gfs2_rbm_incr
  GFS2: Introduce rbm field bii
  GFS2: Do not reset flags on active reservations
  GFS2: introduce bi_blocks for optimization
  GFS2: optimize rbm_from_block wrt bi_start
  GFS2: d_splice_alias() can't return error

GFS2: Use lockref for glocks

2013-10-15T14:18:08+00:00

Currently glocks have an atomic reference count and also a spinlock
which covers various internal fields, such as the state. This intent of
this patch is to replace the spinlock and the atomic reference count
with a lockref structure. This contains a spinlock which we can continue
to use as before, and a reference counter which is used in conjuction
with the spinlock to replace the previous atomic counter.

As a result of this there are some new rules for reference counting on
glocks. We need to distinguish between reference count changes under
gl_spin (which are now just increment or decrement of the new counter,
provided the count cannot hit zero) and those which are outside of
gl_spin, but which now take gl_spin internally.

The conversion is relatively straight forward. There is probably some
further clean up which can be done, but the priority at this stage is to
make the change in as simple a manner as possible.

A consequence of this change is that the reference count is being
decoupled from the lru list processing. This should allow future
adoption of the lru_list code with glocks in due course.

The reason for using the "dead" state and not just relying on 0 being
the "invalid state" is so that in due course 0 ref counts can be
allowable. The intent is to eventually be able to remove the ref count
changes which are currently hidden away in state_change().

Signed-off-by: Steven Whitehouse

lockref: use arch_mutex_cpu_relax() in CMPXCHG_LOOP()

2013-09-28T10:46:24+00:00

Make use of arch_mutex_cpu_relax() so architectures can override the
default cpu_relax() semantics.
This is especially useful for s390, where cpu_relax() means that we
yield() the current (virtual) cpu and therefore is very expensive,
and would contradict the whole purpose of the lockless cmpxchg loop.

Signed-off-by: Heiko Carstens

lockref: allow relaxed cmpxchg64 variant for lockless updates

2013-09-27T16:15:01+00:00

The 64-bit cmpxchg operation on the lockref is ordered by virtue of
hazarding between the cmpxchg operation and the reference count
manipulation. On weakly ordered memory architectures (such as ARM), it
can be of great benefit to omit the barrier instructions where they are
not needed.

This patch moves the lockless lockref code over to a cmpxchg64_relaxed
operation, which doesn't provide barrier semantics. If the operation
isn't defined, we simply #define it as the usual 64-bit cmpxchg macro.

Cc: Waiman Long 
Signed-off-by: Will Deacon 
Signed-off-by: Linus Torvalds