Commit Graph

137 Commits

Author SHA1 Message Date
Mauro Carvalho Chehab
bff9e34c67 docs: fix broken doc references due to renames
Some files got renamed but probably due to some merge conflicts,
a few references still point to the old locations.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
2019-07-17 06:57:51 -03:00
Linus Torvalds
e9a83bd232 It's been a relatively busy cycle for docs:
- A fair pile of RST conversions, many from Mauro.  These create more
    than the usual number of simple but annoying merge conflicts with other
    trees, unfortunately.  He has a lot more of these waiting on the wings
    that, I think, will go to you directly later on.
 
  - A new document on how to use merges and rebases in kernel repos, and one
    on Spectre vulnerabilities.
 
  - Various improvements to the build system, including automatic markup of
    function() references because some people, for reasons I will never
    understand, were of the opinion that :c:func:``function()`` is
    unattractive and not fun to type.
 
  - We now recommend using sphinx 1.7, but still support back to 1.4.
 
  - Lots of smaller improvements, warning fixes, typo fixes, etc.
 -----BEGIN PGP SIGNATURE-----
 
 iQFDBAABCAAtFiEEIw+MvkEiF49krdp9F0NaE2wMflgFAl0krAEPHGNvcmJldEBs
 d24ubmV0AAoJEBdDWhNsDH5Yg98H/AuLqO9LpOgUjF4LhyjxGPdzJkY9RExSJ7km
 gznyreLCZgFaJR+AY6YDsd4Jw6OJlPbu1YM/Qo3C3WrZVFVhgL/s2ebvBgCo50A8
 raAFd8jTf4/mGCHnAqRotAPQ3mETJUk315B66lBJ6Oc+YdpRhwXWq8ZW2bJxInFF
 3HDvoFgMf0KhLuMHUkkL0u3fxH1iA+KvDu8diPbJYFjOdOWENz/CV8wqdVkXRSEW
 DJxIq89h/7d+hIG3d1I7Nw+gibGsAdjSjKv4eRKauZs4Aoxd1Gpl62z0JNk6aT3m
 dtq4joLdwScydonXROD/Twn2jsu4xYTrPwVzChomElMowW/ZBBY=
 =D0eO
 -----END PGP SIGNATURE-----

Merge tag 'docs-5.3' of git://git.lwn.net/linux

Pull Documentation updates from Jonathan Corbet:
 "It's been a relatively busy cycle for docs:

   - A fair pile of RST conversions, many from Mauro. These create more
     than the usual number of simple but annoying merge conflicts with
     other trees, unfortunately. He has a lot more of these waiting on
     the wings that, I think, will go to you directly later on.

   - A new document on how to use merges and rebases in kernel repos,
     and one on Spectre vulnerabilities.

   - Various improvements to the build system, including automatic
     markup of function() references because some people, for reasons I
     will never understand, were of the opinion that
     :c:func:``function()`` is unattractive and not fun to type.

   - We now recommend using sphinx 1.7, but still support back to 1.4.

   - Lots of smaller improvements, warning fixes, typo fixes, etc"

* tag 'docs-5.3' of git://git.lwn.net/linux: (129 commits)
  docs: automarkup.py: ignore exceptions when seeking for xrefs
  docs: Move binderfs to admin-guide
  Disable Sphinx SmartyPants in HTML output
  doc: RCU callback locks need only _bh, not necessarily _irq
  docs: format kernel-parameters -- as code
  Doc : doc-guide : Fix a typo
  platform: x86: get rid of a non-existent document
  Add the RCU docs to the core-api manual
  Documentation: RCU: Add TOC tree hooks
  Documentation: RCU: Rename txt files to rst
  Documentation: RCU: Convert RCU UP systems to reST
  Documentation: RCU: Convert RCU linked list to reST
  Documentation: RCU: Convert RCU basic concepts to reST
  docs: filesystems: Remove uneeded .rst extension on toctables
  scripts/sphinx-pre-install: fix out-of-tree build
  docs: zh_CN: submitting-drivers.rst: Remove a duplicated Documentation/
  Documentation: PGP: update for newer HW devices
  Documentation: Add section about CPU vulnerabilities for Spectre
  Documentation: platform: Delete x86-laptop-drivers.txt
  docs: Note that :c:func: should no longer be used
  ...
2019-07-09 12:34:26 -07:00
Mauro Carvalho Chehab
b640fbad2d docs: pci: fix broken links due to conversion from pci.txt to pci.rst
Some documentation files were still pointing to the old place.

Fixes: 229b4e0728 ("Documentation: PCI: convert pci.txt to reST")
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-06-08 13:42:37 -06:00
Paul E. McKenney
714b6904e2 doc: Remove ".vnet" from paulmck email addresses
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-05-28 09:02:57 -07:00
Will Deacon
9726840d9c docs/memory-barriers.txt: Update I/O section to be clearer about CPU vs thread
The revised I/O ordering section of memory-barriers.txt introduced in
4614bbdee3 ("docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER
EFFECTS" section") loosely refers to "the CPU", whereas the ordering
guarantees generally apply within a thread of execution that can migrate
between cores, with the scheduler providing the relevant barrier
semantics.

Reword the section to refer to "CPU thread" and call out ordering of
MMIO writes separately from ordering of writes to memory. Ben also
spotted that the string accessors are native-endian, so fix that up too.

Link: https://lkml.kernel.org/r/080d1ec73e3e29d6ffeeeb50b39b613da28afb37.camel@kernel.crashing.org
Fixes: 4614bbdee3 ("docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section")
Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2019-04-23 13:34:17 +01:00
Will Deacon
0cde62a46e docs/memory-barriers.txt: Fix style, spacing and grammar in I/O section
Commit 4614bbdee3 ("docs/memory-barriers.txt: Rewrite "KERNEL I/O
BARRIER EFFECTS" section") rewrote the I/O ordering section of
memory-barriers.txt.

Subsequently, Ingo noticed a number of issues with the style, spacing
and grammar of the rewritten section. Fix them based on his suggestions.

Link: https://lkml.kernel.org/r/20190410105833.GA116161@gmail.com
Fixes: 4614bbdee3 ("docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section")
Reported-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2019-04-11 12:02:40 +01:00
Will Deacon
915530396c Documentation: Kill all references to mmiowb()
The guarantees provided by mmiowb() are now provided implicitly by
spin_unlock(), so remove all references to this most confusing of
barriers from our Documentation.

Good riddance.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2019-04-08 12:00:45 +01:00
Will Deacon
4614bbdee3 docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section
The "KERNEL I/O BARRIER EFFECTS" section of memory-barriers.txt is vague,
x86-centric, out-of-date, incomplete and demonstrably incorrect in places.
This is largely because I/O ordering is a horrible can of worms, but also
because the document has stagnated as our understanding has evolved.

Attempt to address some of that, by rewriting the section based on
recent(-ish) discussions with Arnd, BenH and others. Maybe one day we'll
find a way to formalise this stuff, but for now let's at least try to
make the English easier to understand.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Daniel Lustig <dlustig@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2019-04-08 11:59:30 +01:00
Will Deacon
806654a966 Documentation: Use "while" instead of "whilst"
Whilst making an unrelated change to some Documentation, Linus sayeth:

  | Afaik, even in Britain, "whilst" is unusual and considered more
  | formal, and "while" is the common word.
  |
  | [...]
  |
  | Can we just admit that we work with computers, and we don't need to
  | use þe eald Englisc spelling of words that most of the world never
  | uses?

dictionary.com refers to the word as "Chiefly British", which is
probably an undesirable attribute for technical documentation.

Replace all occurrences under Documentation/ with "while".

Cc: David Howells <dhowells@redhat.com>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michael Halcrow <mhalcrow@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-11-20 09:30:43 -07:00
Andrea Parri
2f359c7ea5 locking/memory-barriers: Replace smp_cond_acquire() with smp_cond_load_acquire()
Amend the changes in commit:

  1f03e8d291 ("locking/barriers: Replace smp_cond_acquire() with smp_cond_load_acquire()")

... by updating the documentation accordingly.

Also remove some obsolete information related to the implementation.

Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Daniel Lustig <dlustig@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/20180926182920.27644-5-paulmck@linux.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-10-02 10:28:05 +02:00
Andrea Parri
7696f9910a sched/Documentation: Update wake_up() & co. memory-barrier guarantees
Both the implementation and the users' expectation [1] for the various
wakeup primitives have evolved over time, but the documentation has not
kept up with these changes: brings it into 2018.

[1] http://lkml.kernel.org/r/20180424091510.GB4064@hirez.programming.kicks-ass.net

Also applied feedback from Alan Stern.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Daniel Lustig <dlustig@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: parri.andrea@gmail.com
Link: http://lkml.kernel.org/r/20180716180605.16115-12-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-07-17 09:30:34 +02:00
Linus Torvalds
92400b8c8b Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
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
  ...
2018-06-04 16:40:11 -07:00
Will Deacon
5846581e35 locking/memory-barriers.txt: Fix broken DMA vs. MMIO ordering example
The section of memory-barriers.txt that describes the dma_Xmb() barriers
has an incorrect example claiming that a wmb() is required after writing
to coherent memory in order for those writes to be visible to a device
before a subsequent MMIO access using writel() can reach the device.

In fact, this ordering guarantee is provided (at significant cost on some
architectures such as arm and power) by writel, so the wmb() is not
necessary. writel_relaxed exists for cases where this ordering is not
required.

Fix the example and update the text to make this clearer.

Reported-by: Sinan Kaya <okaya@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: stern@rowland.harvard.edu
Link: http://lkml.kernel.org/r/1526338533-6044-1-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-05-15 08:11:13 +02:00
Mauro Carvalho Chehab
d8a121e3d5 docs: core-api: add circular-buffers documentation
The circular-buffers.txt is already in ReST format. So, move it to the
core-api guide, where it belongs.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-05-08 10:07:06 -06:00
Mauro Carvalho Chehab
de0f51e4b1 docs: core-api: add cachetlb documentation
The cachetlb.txt is already in ReST format. So, move it to the
core-api guide, where it belongs.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-05-08 10:02:34 -06:00
Paul E. McKenney
f28f0868fe locking/memory-barriers: De-emphasize smp_read_barrier_depends() some more
This commit makes further changes to memory-barrier.txt to further
de-emphasize smp_read_barrier_depends(), but leaving some discussion
for historical purposes.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: stern@rowland.harvard.edu
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1520443660-16858-1-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-03-10 10:22:22 +01:00
Nikolay Borisov
51de78892b memory-barriers: Fix description of data dependency barriers
In the description of data dependency barriers the words 'before' is
used erroneously. Since such barrier order dependent loads one after
the other. So substitute 'before' with 'after'.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: stern@rowland.harvard.edu
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1519169112-20593-8-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-02-21 09:58:14 +01:00
Andrea Parri
621df431b0 Documentation/memory-barriers.txt: Cross-reference "tools/memory-model/"
A memory consistency model is now available for the Linux kernel [1],
which "can (roughly speaking) be thought of as an automated version of
memory-barriers.txt" and which is (in turn) "accompanied by extensive
documentation on its use and its design".

Inform the (occasional) reader of memory-barriers.txt of these
developments.

[1] https://marc.info/?l=linux-kernel&m=151687290114799&w=2

Co-developed-by: Andrea Parri <parri.andrea@gmail.com>
Co-developed-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: nborisov@suse.com
Cc: npiggin@gmail.com
Cc: stern@rowland.harvard.edu
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1519169112-20593-7-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-02-21 09:58:14 +01:00
Paul E. McKenney
9ad3c143d7 doc: De-emphasize smp_read_barrier_depends
This commit keeps only the historical and low-level discussion of
smp_read_barrier_depends().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Adjusted to allow for David Howells feedback on prior commit. ]
2017-12-05 11:57:53 -08:00
Paul E. McKenney
4055594644 doc: READ_ONCE() now implies smp_barrier_depends()
This commit updates an example in memory-barriers.txt to account for
the fact that READ_ONCE() now implies smp_barrier_depends().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Added MEMORY_BARRIER instructions from DEC Alpha from
  READ_ONCE(), per David Howells's feedback. ]
2017-12-04 10:50:08 -08:00
Linus Torvalds
8e9a2dba86 Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core locking updates from Ingo Molnar:
 "The main changes in this cycle are:

   - Another attempt at enabling cross-release lockdep dependency
     tracking (automatically part of CONFIG_PROVE_LOCKING=y), this time
     with better performance and fewer false positives. (Byungchul Park)

   - Introduce lockdep_assert_irqs_enabled()/disabled() and convert
     open-coded equivalents to lockdep variants. (Frederic Weisbecker)

   - Add down_read_killable() and use it in the VFS's iterate_dir()
     method. (Kirill Tkhai)

   - Convert remaining uses of ACCESS_ONCE() to
     READ_ONCE()/WRITE_ONCE(). Most of the conversion was Coccinelle
     driven. (Mark Rutland, Paul E. McKenney)

   - Get rid of lockless_dereference(), by strengthening Alpha atomics,
     strengthening READ_ONCE() with smp_read_barrier_depends() and thus
     being able to convert users of lockless_dereference() to
     READ_ONCE(). (Will Deacon)

   - Various micro-optimizations:

        - better PV qspinlocks (Waiman Long),
        - better x86 barriers (Michael S. Tsirkin)
        - better x86 refcounts (Kees Cook)

   - ... plus other fixes and enhancements. (Borislav Petkov, Juergen
     Gross, Miguel Bernal Marin)"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
  locking/x86: Use LOCK ADD for smp_mb() instead of MFENCE
  rcu: Use lockdep to assert IRQs are disabled/enabled
  netpoll: Use lockdep to assert IRQs are disabled/enabled
  timers/posix-cpu-timers: Use lockdep to assert IRQs are disabled/enabled
  sched/clock, sched/cputime: Use lockdep to assert IRQs are disabled/enabled
  irq_work: Use lockdep to assert IRQs are disabled/enabled
  irq/timings: Use lockdep to assert IRQs are disabled/enabled
  perf/core: Use lockdep to assert IRQs are disabled/enabled
  x86: Use lockdep to assert IRQs are disabled/enabled
  smp/core: Use lockdep to assert IRQs are disabled/enabled
  timers/hrtimer: Use lockdep to assert IRQs are disabled/enabled
  timers/nohz: Use lockdep to assert IRQs are disabled/enabled
  workqueue: Use lockdep to assert IRQs are disabled/enabled
  irq/softirqs: Use lockdep to assert IRQs are disabled/enabled
  locking/lockdep: Add IRQs disabled/enabled assertion APIs: lockdep_assert_irqs_enabled()/disabled()
  locking/pvqspinlock: Implement hybrid PV queued/unfair locks
  locking/rwlocks: Fix comments
  x86/paravirt: Set up the virt_spin_lock_key after static keys get initialized
  block, locking/lockdep: Assign a lock_class per gendisk used for wait_for_completion()
  workqueue: Remove now redundant lock acquisitions wrt. workqueue flushes
  ...
2017-11-13 12:38:26 -08:00
Will Deacon
59ecbbe7b3 locking/barriers: Kill lockless_dereference()
lockless_dereference() is a nice idea, but it gained little traction in
kernel code since its introduction three years ago. This is partly
because it's a pain to type, but also because using READ_ONCE() instead
has worked correctly on all architectures apart from Alpha, which is a
fully supported but somewhat niche architecture these days.

Now that READ_ONCE() has been upgraded to contain an implicit
smp_read_barrier_depends() and the few callers of lockless_dereference()
have been converted, we can remove lockless_dereference() altogether.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1508840570-22169-5-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-10-24 13:17:33 +02:00
Guilherme G. Piccoli
5692fcc671 doc: Rewrite confusing statement about memory barriers
The "Write (or store) memory barriers" bullet of the "Variety of memory
barriers" section, calls out a sequential order of stores, which is
confusing since sequential ordering is not guaranteed.

This commit therefore rewords to avoid mentioning a sequence of stores
to clarify the intent.

Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-10-20 11:09:32 -07:00
Scott Tsai
d92f842bb3 memory-barriers.txt: Fix typo in pairing example
In the "general barrier pairing with implicit control depdendency"
example, the last write by CPU 1 was meant to change variable x and not
y. The example would be pretty uninteresting if no CPU ever changes x
and the variable was initialized to zero.

Signed-off-by: Scott Tsai <scottt@scottt.tw>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-10-20 11:09:32 -07:00
Alan Stern
0902b1f44a memory-barriers: Rework multicopy-atomicity section
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-10-09 14:23:37 -07:00
Paul E. McKenney
f1ab25a30c memory-barriers: Replace uses of "transitive"
The current version of memory-barriers.txt misuses the term "transitive",
so this commit replaces it with multi-copy atomic, also adding a
definition of this term.

Reported-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-10-09 14:23:36 -07:00
Linus Torvalds
5f82e71a00 Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:

 - Add 'cross-release' support to lockdep, which allows APIs like
   completions, where it's not the 'owner' who releases the lock, to be
   tracked. It's all activated automatically under
   CONFIG_PROVE_LOCKING=y.

 - Clean up (restructure) the x86 atomics op implementation to be more
   readable, in preparation of KASAN annotations. (Dmitry Vyukov)

 - Fix static keys (Paolo Bonzini)

 - Add killable versions of down_read() et al (Kirill Tkhai)

 - Rework and fix jump_label locking (Marc Zyngier, Paolo Bonzini)

 - Rework (and fix) tlb_flush_pending() barriers (Peter Zijlstra)

 - Remove smp_mb__before_spinlock() and convert its usages, introduce
   smp_mb__after_spinlock() (Peter Zijlstra)

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (56 commits)
  locking/lockdep/selftests: Fix mixed read-write ABBA tests
  sched/completion: Avoid unnecessary stack allocation for COMPLETION_INITIALIZER_ONSTACK()
  acpi/nfit: Fix COMPLETION_INITIALIZER_ONSTACK() abuse
  locking/pvqspinlock: Relax cmpxchg's to improve performance on some architectures
  smp: Avoid using two cache lines for struct call_single_data
  locking/lockdep: Untangle xhlock history save/restore from task independence
  locking/refcounts, x86/asm: Disable CONFIG_ARCH_HAS_REFCOUNT for the time being
  futex: Remove duplicated code and fix undefined behaviour
  Documentation/locking/atomic: Finish the document...
  locking/lockdep: Fix workqueue crossrelease annotation
  workqueue/lockdep: 'Fix' flush_work() annotation
  locking/lockdep/selftests: Add mixed read-write ABBA tests
  mm, locking/barriers: Clarify tlb_flush_pending() barriers
  locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE and CONFIG_LOCKDEP_COMPLETIONS truly non-interactive
  locking/lockdep: Explicitly initialize wq_barrier::done::map
  locking/lockdep: Rename CONFIG_LOCKDEP_COMPLETE to CONFIG_LOCKDEP_COMPLETIONS
  locking/lockdep: Reword title of LOCKDEP_CROSSRELEASE config
  locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE part of CONFIG_PROVE_LOCKING
  locking/refcounts, x86/asm: Implement fast refcount overflow protection
  locking/lockdep: Fix the rollback and overwrite detection logic in crossrelease
  ...
2017-09-04 11:52:29 -07:00
Paul E. McKenney
66ce3a4dcb doc: Update memory-barriers.txt for read-to-write dependencies
The memory-barriers.txt document contains an obsolete passage stating that
smp_read_barrier_depends() is required to force ordering for read-to-write
dependencies.  We now know that this is not required, even for DEC Alpha.
This commit therefore updates this passage to state that read-to-write
dependencies are respected even without smp_read_barrier_depends().

Reported-by: Lance Roy <ldr709@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Luc Maranget <luc.maranget@inria.fr>
[ paulmck: Reference control-dependencies sections and use WRITE_ONCE()
  per Will Deacon.  Correctly place split-cache paragraph while there. ]
Acked-by: Will Deacon <will.deacon@arm.com>
2017-08-17 07:29:57 -07:00
Peter Zijlstra
a9668cd6ee locking: Remove smp_mb__before_spinlock()
Now that there are no users of smp_mb__before_spinlock() left, remove
it entirely.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-08-10 12:29:03 +02:00
Peter Zijlstra
706eeb3e9c Documentation/locking/atomic: Add documents for new atomic_t APIs
Since we've vastly expanded the atomic_t interface in recent years the
existing documentation is woefully out of date and people seem to get
confused a bit.

Start a new document to hopefully better explain the current state of
affairs.

The old atomic_ops.txt also covers bitmaps and a few more details so
this is not a full replacement and we'll therefore keep that document
around until such a time that we've managed to write more text to cover
its entire.

Also please, ReST people, go away.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-08-10 12:29:00 +02:00
Linus Torvalds
954e6e03c6 A set of fixes for various warnings, including the one caused by the
removal of kernel/rcu/srcu.c.  Also correct a stray pointer in
 memory-barriers.txt.
 -----BEGIN PGP SIGNATURE-----
 
 iQIcBAABAgAGBQJZZqwLAAoJEI3ONVYwIuV6KJoP/0Ci87obaOe/zBCgPN+bNPD3
 QCe4HjihMKHmXNJbqX2kQFHwrruKKa6mS/OfKGy+UOmGVcBdNlOvMm2NjV4npw2P
 Av9HUmSiheaVIgWkbkv4Ov705DxAd3G8SqKwau34jNSajg1LmtStcEAwgM7yXQNb
 /+r2i4SWG+S5MnuJQ319qtYHyBBoXjY0PcMAaPL+n6xJ/Lt7pFjHqXuHe+rjH44U
 a7NODob3zquHELmqu3gIDNvnnaRR4yHmk66bYa4jFqRf9CIvuY3DrnM61gWq69vb
 ROv7rLKX8VEE8RShx4Gn+F6akEPYTUtTCRO8dKeT0RK4nPlhVeObF1Fq+9Ttj1xx
 SvmDhp3Kq/xI6aXXH76THOMxwoi6bykZFfZoi3zD7d6PQBmdwGPKDxPRMVOzsUqS
 E2DIo/8LSReWGoqat51DjmHAg5npoxSdcuw0BU++OVaoDTYCQ2iaPn5htIiQ/8SM
 jG4fjgMJB9I6ub/RrxVSTPPSgYC/bdRTSH0q4D7lC5/uh4jAhSM2GMtwprejQ//k
 DgUaY1UHutVnpGoceRE0jw3nj5mZZ9ILr/5iRYOztemjCJOSa/MSfyVkgRObmOKc
 P6ihr0QZq34nwOL0K/JTQml+NuszcDy53+hBIOdXhikl4wsy0BjbYysFC5gzH4V3
 DhIRdwTeTKleq0tnKNOl
 =JEoA
 -----END PGP SIGNATURE-----

Merge tag '4.13-fixes' of git://git.lwn.net/linux

Pull documentation fixes from Jonathan Corbet:
 "A set of fixes for various warnings, including the one caused by the
  removal of kernel/rcu/srcu.c. Also correct a stray pointer in
  memory-barriers.txt"

* tag '4.13-fixes' of git://git.lwn.net/linux:
  kokr/memory-barriers.txt: Fix obsolete link to atomic_ops.txt
  memory-barriers.txt: Fix broken link to atomic_ops.txt
  docs: Turn off section numbering for the input docs
  docs: Include uaccess docs from the right file
  docs: Do not include from kernel/rcu/srcu.c
2017-07-13 13:44:54 -07:00
SeongJae Park
3afadfd902 memory-barriers.txt: Fix broken link to atomic_ops.txt
Few obsolete links to atomic_ops.txt exist in memory-barriers.txt though
the file has moved to core-api/atomic_ops.rst.  This commit fixes the
obsolete links.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-07-12 16:56:30 -06:00
Linus Torvalds
650fc870a2 There has been a fair amount of activity in the docs tree this time
around.  Highlights include:
 
  - Conversion of a bunch of security documentation into RST
 
  - The conversion of the remaining DocBook templates by The Amazing
    Mauro Machine.  We can now drop the entire DocBook build chain.
 
  - The usual collection of fixes and minor updates.
 -----BEGIN PGP SIGNATURE-----
 
 iQIcBAABAgAGBQJZWkGAAAoJEI3ONVYwIuV6rf0P/0B3JTiVPKS/WUx53+jzbAi4
 1BN7dmmuMxE1bWpgdEq+ac4aKxm07iAojuntuMj0qz/ZB1WARcmvEqqzI5i4wfq9
 5MrLduLkyuWfr4MOPseKJ2VK83p8nkMOiO7jmnBsilu7fE4nF+5YY9j4cVaArfMy
 cCQvAGjQzvej2eiWMGUSLHn4QFKh00aD7cwKyBVsJ08b27C9xL0J2LQyCDZ4yDgf
 37/MH3puEd3HX/4qAwLonIxT3xrIrrbDturqLU7OSKcWTtGZNrYyTFbwR3RQtqWd
 H8YZVg2Uyhzg9MYhkbQ2E5dEjUP4mkegcp6/JTINH++OOPpTbdTJgirTx7VTkSf1
 +kL8t7+Ayxd0FH3+77GJ5RMj8LUK6rj5cZfU5nClFQKWXP9UL3IelQ3Nl+SpdM8v
 ZAbR2KjKgH9KS6+cbIhgFYlvY+JgPkOVruwbIAc7wXVM3ibk1sWoBOFEujcbueWh
 yDpQv3l1UX0CKr3jnevJoW26LtEbGFtC7gSKZ+3btyeSBpWFGlii42KNycEGwUW0
 ezlwryDVHzyTUiKllNmkdK4v73mvPsZHEjgmme4afKAIiUilmcUF4XcqD86hISFT
 t+UJLA/zEU+0sJe26o2nK6GNJzmo4oCtVyxfhRe26Ojs1n80xlYgnZRfuIYdd31Z
 nwLBnwDCHAOyX91WXp9G
 =cVjZ
 -----END PGP SIGNATURE-----

Merge tag 'docs-4.13' of git://git.lwn.net/linux

Pull documentation updates from Jonathan Corbet:
 "There has been a fair amount of activity in the docs tree this time
  around. Highlights include:

   - Conversion of a bunch of security documentation into RST

   - The conversion of the remaining DocBook templates by The Amazing
     Mauro Machine. We can now drop the entire DocBook build chain.

   - The usual collection of fixes and minor updates"

* tag 'docs-4.13' of git://git.lwn.net/linux: (90 commits)
  scripts/kernel-doc: handle DECLARE_HASHTABLE
  Documentation: atomic_ops.txt is core-api/atomic_ops.rst
  Docs: clean up some DocBook loose ends
  Make the main documentation title less Geocities
  Docs: Use kernel-figure in vidioc-g-selection.rst
  Docs: fix table problems in ras.rst
  Docs: Fix breakage with Sphinx 1.5 and upper
  Docs: Include the Latex "ifthen" package
  doc/kokr/howto: Only send regression fixes after -rc1
  docs-rst: fix broken links to dynamic-debug-howto in kernel-parameters
  doc: Document suitability of IBM Verse for kernel development
  Doc: fix a markup error in coding-style.rst
  docs: driver-api: i2c: remove some outdated information
  Documentation: DMA API: fix a typo in a function name
  Docs: Insert missing space to separate link from text
  doc/ko_KR/memory-barriers: Update control-dependencies example
  Documentation, kbuild: fix typo "minimun" -> "minimum"
  docs: Fix some formatting issues in request-key.rst
  doc: ReSTify keys-trusted-encrypted.txt
  doc: ReSTify keys-request-key.txt
  ...
2017-07-03 21:13:25 -07:00
Palmer Dabbelt
f5620df7e3 Documentation: atomic_ops.txt is core-api/atomic_ops.rst
I was reading the memory barries documentation in order to make sure the
RISC-V barries were correct, and I found a broken link to the atomic
operations documentation.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-06-24 08:13:43 -06:00
Stan Drozd
35bdc72a33 docs: Fix typo in Documentation/memory-barriers.txt
This commit changes "architecure" to the correct spelling,
"architecture".

Signed-off-by: Stan Drozd <drozdziak1@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08 08:25:29 -07:00
Linus Torvalds
09d79d1033 Connect the newly RST-formatted documentation to the rest; this had to wait
until the input pull was done.  There's also a few small fixes that
 wandered in.
 -----BEGIN PGP SIGNATURE-----
 
 iQIcBAABAgAGBQJZFKWWAAoJEI3ONVYwIuV6e1QP/iuwl4dBo9wl8KZAarErCWSf
 uAXx33ca4dnPOoxbDwRtg41ioSrF69vVjJp35oyBBSOVyDhQiLvec0Fq6EGObRo4
 Xsoe0JwvadqY+aTETxXm3Id4aZHk3OMyCtZRinomeU9tN5dRNQaffvLG6Rtl7JK2
 /tlqeNTmD1hLoD7azuvhwKfPYWDaYvmqd5I6F/2ANhYyJSg7pivpuN3Xfpf8GaiG
 wmaCqF0OLKBXfTPQwC69YX7PPye3AOGUbIYt6RwfVhutKkXjazsH7n3vSJD63UFn
 8/1eh+UjOGWfriz5oih3DTd+Hf1A7KhRCyxoOSReo78Z3k3YXqmOFgCCgfE0oX71
 2WIdEBHiNnHNH8bdaTMIfqjG0JvNzYmXq+uXvHWiW8juhE/2ZhNRG+uyrRiADctm
 TWjC4v219yY5h2IMcfyWOyLi1q/4zM3nmc8J1Ia+J9jH6ICKM+8sMrHaMyoSlCIQ
 FcYe6gQdD1NepV675QiZUObCxUWu840jNSqYtF+0Ck/DREJKDEAdS7cmCxfDSAgf
 oh6LsSHZy8tMyeOa9Wf9d5EPzK/eqd7x/vMKPI3jaETrwdXZzjO6Bn3codWx/gl6
 7E/xqE8qCremcOWHIyx9jhd6T38swD+NScLU9CfRCKh+mddRDy3IiXD6NBo+m6Rq
 echBXgxl/P0CIck2W4Ql
 =Zk24
 -----END PGP SIGNATURE-----

Merge tag 'docs-4.12-2' of git://git.lwn.net/linux

Pull more documentation updates from Jonathan Corbet:
 "Connect the newly RST-formatted documentation to the rest; this had to
  wait until the input pull was done. There's also a few small fixes
  that wandered in"

* tag 'docs-4.12-2' of git://git.lwn.net/linux:
  doc: replace FTP URL to kernel.org with HTTPS one
  docs: update references to the device io book
  Documentation: earlycon: fix Marvell Armada 3700 UART name
  docs-rst: add input docs at main index and use kernel-figure
2017-05-11 11:29:52 -07:00
Helmut Grohne
0fe397f0c6 docs: update references to the device io book
While converting the deviceiobook from DocBook to RST, dangling
references were left behind. This commit updates all remaining
references to the new location. SeongJae Park improved the ko_KR
translation.

Fixes: 8a8a602fdb ("docs: Convert the deviceio template to RST")
Signed-off-by: Helmut Grohne <h.grohne@intenta.de>
Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-05-09 13:44:56 -06:00
pierre Kuo
b26cfc48e3 doc: Update control-dependencies section of memory-barriers.txt
In the following example, if MAX is defined to be 1, then the compiler
knows (Q % MAX) is equal to zero.  The compiler can therefore throw
away the "then" branch (and the "if"), retaining only the "else" branch.

	q = READ_ONCE(a);
	if (q % MAX) {
		WRITE_ONCE(b, 1);
		do_something();
	} else {
		WRITE_ONCE(b, 2);
		do_something_else();
	}

It is therefore necessary to modify the example like this:

        q = READ_ONCE(a);
-       WRITE_ONCE(b, 1);
+       WRITE_ONCE(b, 2);
        do_something_else();

Signed-off-by: pierre Kuo <vichy.kuo@gmail.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-04-12 08:23:43 -07:00
Paul E. McKenney
c8241f8553 doc: Update control-dependencies section of memory-barriers.txt
This commit adds consistency to examples, formatting, and a couple of
additional warnings.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2017-01-14 21:29:15 -08:00
SeongJae Park
8b9e771555 locking/Documentation: Fix a typo of example result
An example result for data dependent write has a typo.  This commit
fixes the wrong typo.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dhowells@redhat.com
Cc: linux-arch@vger.kernel.org
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1470939463-31950-3-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-08-12 08:24:13 +02:00
SeongJae Park
d7cab36db8 locking/Documentation: Fix wrong section reference
Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dhowells@redhat.com
Cc: linux-arch@vger.kernel.org
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1470939463-31950-2-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-08-12 08:24:13 +02:00
SeongJae Park
dfeccea617 locking/Documentation: Maintain consistent blank line
Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dhowells@redhat.com
Cc: linux-arch@vger.kernel.org
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1470939463-31950-1-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-08-12 08:24:13 +02:00
Paul E. McKenney
ebff09a6ff locking/Documentation: Clarify limited control-dependency scope
Nothing in the control-dependencies section of memory-barriers.txt
says that control dependencies don't extend beyond the end of the
if-statement containing the control dependency.  Worse yet, in many
situations, they do extend beyond that if-statement.  In particular,
the compiler cannot destroy the control dependency given proper use of
READ_ONCE() and WRITE_ONCE().  However, a weakly ordered system having
a conditional-move instruction provides the control-dependency guarantee
only to code within the scope of the if-statement itself.

This commit therefore adds words and an example demonstrating this
limitation of control dependencies.

Reported-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: corbet@lwn.net
Cc: linux-arch@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Link: http://lkml.kernel.org/r/20160615230817.GA18039@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-06-17 09:54:45 +02:00
Will Deacon
3cfe2e8bc1 locking/Documentation: Clarify that ACQUIRE applies to loads, RELEASE applies to stores
For compound atomics performing both a load and a store operation, make
it clear that _acquire and _release variants refer only to the load and
store portions of compound atomic. For example, xchg_acquire is an xchg
operation where the load takes on ACQUIRE semantics.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: corbet@lwn.net
Cc: dave@stgolabs.net
Cc: dhowells@redhat.com
Cc: linux-doc@vger.kernel.org
Link: http://lkml.kernel.org/r/1461691328-5429-3-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-28 10:57:51 +02:00
David Howells
8d4840e848 locking/Documentation: State purpose of memory-barriers.txt
There has been some confusion about the purpose of memory-barriers.txt,
so this commit adds a statement of purpose.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: corbet@lwn.net
Cc: dave@stgolabs.net
Cc: linux-doc@vger.kernel.org
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1461691328-5429-2-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-28 10:57:51 +02:00
Peter Zijlstra
e7720af5f9 locking/Documentation: Add disclaimer
It appears people are reading this document as a requirements list for
building hardware. This is not the intent of this document. Nor is it
particularly suited for this purpose.

The primary purpose of this document is our collective attempt to define
a set of primitives that (hopefully) allow us to write correct code on
the myriad of SMP platforms Linux supports.

Its a definite work in progress as our understanding of these platforms,
and memory ordering in general, progresses.

Nor does being mentioned in this document mean we think its a
particularly good idea; the data dependency barrier required by Alpha
being a prime example. Yes we have it, no you're insane to require it
when building new hardware.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: corbet@lwn.net
Cc: dave@stgolabs.net
Cc: dhowells@redhat.com
Cc: linux-doc@vger.kernel.org
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1461691328-5429-1-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-28 10:57:51 +02:00
Davidlohr Bueso
787df6383c locking/Documentation: Mention smp_cond_acquire()
... do this next to smp_load_acquire() when first mentioning
ACQUIRE. While this call is briefly explained and control
dependencies are mentioned later, it does not hurt the reader.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bobby.prani@gmail.com
Cc: dhowells@redhat.com
Cc: dipankar@in.ibm.com
Cc: dvhart@linux.intel.com
Cc: edumazet@google.com
Cc: fweisbec@gmail.com
Cc: jiangshanlai@gmail.com
Cc: josh@joshtriplett.org
Cc: mathieu.desnoyers@efficios.com
Cc: oleg@redhat.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/1460476375-27803-7-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-13 08:52:23 +02:00
SeongJae Park
0b6fa347dc locking/Documentation: Insert white spaces consistently
The document uses two newlines between sections, one newline between
item and its detailed description, and two spaces between sentences.

There are a few places that used these rules inconsistently - fix them.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: David Howells <dhowells@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bobby.prani@gmail.com
Cc: dipankar@in.ibm.com
Cc: dvhart@linux.intel.com
Cc: edumazet@google.com
Cc: fweisbec@gmail.com
Cc: jiangshanlai@gmail.com
Cc: josh@joshtriplett.org
Cc: mathieu.desnoyers@efficios.com
Cc: oleg@redhat.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/1460476375-27803-5-git-send-email-paulmck@linux.vnet.ibm.com
[ Fixed the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-13 08:52:22 +02:00
SeongJae Park
3dbf0913f6 locking/Documentation: Fix formatting inconsistencies
Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: David Howells <dhowells@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bobby.prani@gmail.com
Cc: dipankar@in.ibm.com
Cc: dvhart@linux.intel.com
Cc: edumazet@google.com
Cc: fweisbec@gmail.com
Cc: jiangshanlai@gmail.com
Cc: josh@joshtriplett.org
Cc: mathieu.desnoyers@efficios.com
Cc: oleg@redhat.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/1460476375-27803-4-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-13 08:52:22 +02:00
SeongJae Park
01e1cd6de8 locking/Documentation: Add missed subsection in TOC
A 'Virtual Machine Guests' subsection was added by this commit:

6a65d26385 ("asm-generic: implement virt_xxx memory barriers")

but the TOC was not updated - update it.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: David Howells <dhowells@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bobby.prani@gmail.com
Cc: dipankar@in.ibm.com
Cc: dvhart@linux.intel.com
Cc: edumazet@google.com
Cc: fweisbec@gmail.com
Cc: jiangshanlai@gmail.com
Cc: josh@joshtriplett.org
Cc: mathieu.desnoyers@efficios.com
Cc: oleg@redhat.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/1460476375-27803-3-git-send-email-paulmck@linux.vnet.ibm.com
[ Rewrote the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-04-13 08:52:22 +02:00