linux-toradex.git/tools/memory-model/Documentation, branch v5.9-rc5 Linux kernel for Apalis and Colibri modules Merge tag 'locking-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2020-08-03T21:39:35+00:00 Linus Torvalds torvalds@linux-foundation.org 2020-08-03T21:39:35+00:00 9ba19ccd2d283a79dd29e8130819c59beca80f62 Pull locking updates from Ingo Molnar: - LKMM updates: mostly documentation changes, but also some new litmus tests for atomic ops. - KCSAN updates: the most important change is that GCC 11 now has all fixes in place to support KCSAN, so GCC support can be enabled again. Also more annotations. - futex updates: minor cleanups and simplifications - seqlock updates: merge preparatory changes/cleanups for the 'associated locks' facilities. - lockdep updates: - simplify IRQ trace event handling - add various new debug checks - simplify header dependencies, split out <linux/lockdep_types.h>, decouple lockdep from other low level headers some more - fix NMI handling - misc cleanups and smaller fixes * tag 'locking-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (60 commits) kcsan: Improve IRQ state trace reporting lockdep: Refactor IRQ trace events fields into struct seqlock: lockdep assert non-preemptibility on seqcount_t write lockdep: Add preemption enabled/disabled assertion APIs seqlock: Implement raw_seqcount_begin() in terms of raw_read_seqcount() seqlock: Add kernel-doc for seqcount_t and seqlock_t APIs seqlock: Reorder seqcount_t and seqlock_t API definitions seqlock: seqcount_t latch: End read sections with read_seqcount_retry() seqlock: Properly format kernel-doc code samples Documentation: locking: Describe seqlock design and usage locking/qspinlock: Do not include atomic.h from qspinlock_types.h locking/atomic: Move ATOMIC_INIT into linux/types.h lockdep: Move list.h inclusion into lockdep.h locking/lockdep: Fix TRACE_IRQFLAGS vs. NMIs futex: Remove unused or redundant includes futex: Consistently use fshared as boolean futex: Remove needless goto's futex: Remove put_futex_key() rwsem: fix commas in initialisation docs: locking: Replace HTTP links with HTTPS ones ... 
Pull locking updates from Ingo Molnar:

 - LKMM updates: mostly documentation changes, but also some new litmus
   tests for atomic ops.

 - KCSAN updates: the most important change is that GCC 11 now has all
   fixes in place to support KCSAN, so GCC support can be enabled again.
   Also more annotations.

 - futex updates: minor cleanups and simplifications

 - seqlock updates: merge preparatory changes/cleanups for the
   'associated locks' facilities.

 - lockdep updates:
    - simplify IRQ trace event handling
    - add various new debug checks
    - simplify header dependencies, split out <linux/lockdep_types.h>,
      decouple lockdep from other low level headers some more
    - fix NMI handling

 - misc cleanups and smaller fixes

* tag 'locking-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (60 commits)
  kcsan: Improve IRQ state trace reporting
  lockdep: Refactor IRQ trace events fields into struct
  seqlock: lockdep assert non-preemptibility on seqcount_t write
  lockdep: Add preemption enabled/disabled assertion APIs
  seqlock: Implement raw_seqcount_begin() in terms of raw_read_seqcount()
  seqlock: Add kernel-doc for seqcount_t and seqlock_t APIs
  seqlock: Reorder seqcount_t and seqlock_t API definitions
  seqlock: seqcount_t latch: End read sections with read_seqcount_retry()
  seqlock: Properly format kernel-doc code samples
  Documentation: locking: Describe seqlock design and usage
  locking/qspinlock: Do not include atomic.h from qspinlock_types.h
  locking/atomic: Move ATOMIC_INIT into linux/types.h
  lockdep: Move list.h inclusion into lockdep.h
  locking/lockdep: Fix TRACE_IRQFLAGS vs. NMIs
  futex: Remove unused or redundant includes
  futex: Consistently use fshared as boolean
  futex: Remove needless goto's
  futex: Remove put_futex_key()
  rwsem: fix commas in initialisation
  docs: locking: Replace HTTP links with HTTPS ones
  ...
tools/memory-model: Remove smp_read_barrier_depends() from informal doc 2020-07-21T09:50:37+00:00 Will Deacon will@kernel.org 2019-11-07T14:44:06+00:00 628fd55671f753a1e4fe8c21b6a0553503cade08 smp_read_barrier_depends() has gone the way of mmiowb() and so many esoteric memory barriers before it. Drop the two mentions of this deceased barrier from the LKMM informal explanation document. Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Alan Stern <stern@rowland.harvard.edu> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Will Deacon <will@kernel.org> 
smp_read_barrier_depends() has gone the way of mmiowb() and so many
esoteric memory barriers before it. Drop the two mentions of this
deceased barrier from the LKMM informal explanation document.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
tools/memory-model: Fix reference to litmus test in recipes.txt 2020-06-29T19:05:18+00:00 Akira Yokosawa akiyks@gmail.com 2020-05-10T04:37:14+00:00 9725dd55512772422e195cf0cfbca1eda6778358 The name of litmus test doesn't match the one described below. Fix the name of litmus test. Acked-by: Andrea Parri <parri.andrea@gmail.com> Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
The name of litmus test doesn't match the one described below.
Fix the name of litmus test.

Acked-by: Andrea Parri <parri.andrea@gmail.com>
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model: Fix "conflict" definition 2020-06-29T19:05:17+00:00 Marco Elver elver@google.com 2020-03-02T17:21:01+00:00 c1b14609013a6b4c4b2d73583bde645540ebd9b7 The definition of "conflict" should not include the type of access nor whether the accesses are concurrent or not, which this patch addresses. The definition of "data race" remains unchanged. The definition of "conflict" as we know it and is cited by various papers on memory consistency models appeared in [1]: "Two accesses to the same variable conflict if at least one is a write; two operations conflict if they execute conflicting accesses." The LKMM as well as the C11 memory model are adaptations of data-race-free, which are based on the work in [2]. Necessarily, we need both conflicting data operations (plain) and synchronization operations (marked). For example, C11's definition is based on [3], which defines a "data race" as: "Two memory operations conflict if they access the same memory location, and at least one of them is a store, atomic store, or atomic read-modify-write operation. In a sequentially consistent execution, two memory operations from different threads form a type 1 data race if they conflict, at least one of them is a data operation, and they are adjacent in <T (i.e., they may be executed concurrently)." [1] D. Shasha, M. Snir, "Efficient and Correct Execution of Parallel Programs that Share Memory", 1988. URL: http://snir.cs.illinois.edu/listed/J21.pdf [2] S. Adve, "Designing Memory Consistency Models for Shared-Memory Multiprocessors", 1993. URL: http://sadve.cs.illinois.edu/Publications/thesis.pdf [3] H.-J. Boehm, S. Adve, "Foundations of the C++ Concurrency Memory Model", 2008. URL: https://www.hpl.hp.com/techreports/2008/HPL-2008-56.pdf Signed-off-by: Marco Elver <elver@google.com> Co-developed-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
The definition of "conflict" should not include the type of access nor
whether the accesses are concurrent or not, which this patch addresses.
The definition of "data race" remains unchanged.

The definition of "conflict" as we know it and is cited by various
papers on memory consistency models appeared in [1]: "Two accesses to
the same variable conflict if at least one is a write; two operations
conflict if they execute conflicting accesses."

The LKMM as well as the C11 memory model are adaptations of
data-race-free, which are based on the work in [2]. Necessarily, we need
both conflicting data operations (plain) and synchronization operations
(marked). For example, C11's definition is based on [3], which defines a
"data race" as: "Two memory operations conflict if they access the same
memory location, and at least one of them is a store, atomic store, or
atomic read-modify-write operation. In a sequentially consistent
execution, two memory operations from different threads form a type 1
data race if they conflict, at least one of them is a data operation,
and they are adjacent in <T (i.e., they may be executed concurrently)."

[1] D. Shasha, M. Snir, "Efficient and Correct Execution of Parallel
    Programs that Share Memory", 1988.
	URL: http://snir.cs.illinois.edu/listed/J21.pdf

[2] S. Adve, "Designing Memory Consistency Models for Shared-Memory
    Multiprocessors", 1993.
	URL: http://sadve.cs.illinois.edu/Publications/thesis.pdf

[3] H.-J. Boehm, S. Adve, "Foundations of the C++ Concurrency Memory
    Model", 2008.
	URL: https://www.hpl.hp.com/techreports/2008/HPL-2008-56.pdf

Signed-off-by: Marco Elver <elver@google.com>
Co-developed-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model: Add recent references 2020-06-29T19:05:17+00:00 Paul E. McKenney paulmck@kernel.org 2020-01-22T21:38:57+00:00 38908de90a8c24c949505958f1d09812bb3b64aa This commit updates the list of LKMM-related publications in Documentation/references.txt. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Acked-by: Andrea Parri <parri.andrea@gmail.com> 
This commit updates the list of LKMM-related publications in
Documentation/references.txt.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
tools/memory-model/Documentation: Add plain accesses and data races to explanation.txt 2019-10-05T18:59:44+00:00 Alan Stern stern@rowland.harvard.edu 2019-10-01T17:40:19+00:00 c58a80170169305f7a088e8ebb61231e3095b5cd This patch updates the Linux Kernel Memory Model's explanation.txt file by adding a section devoted to the model's handling of plain accesses and data-race detection. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
This patch updates the Linux Kernel Memory Model's explanation.txt
file by adding a section devoted to the model's handling of plain
accesses and data-race detection.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model/Documentation: Put redefinition of rcu-fence into explanation.txt 2019-10-05T18:59:23+00:00 Alan Stern stern@rowland.harvard.edu 2019-10-01T17:40:11+00:00 ddc82999f02580f93f9be2b8fb3b10f6139fb281 This patch updates the Linux Kernel Memory Model's explanation.txt file to incorporate the introduction of the rcu-order relation and the redefinition of rcu-fence made by commit 15aa25cbf0cc ("tools/memory-model: Change definition of rcu-fence"). Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
This patch updates the Linux Kernel Memory Model's explanation.txt
file to incorporate the introduction of the rcu-order relation and
the redefinition of rcu-fence made by commit 15aa25cbf0cc
("tools/memory-model: Change definition of rcu-fence").

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model/Documentation: Fix typos in explanation.txt 2019-10-05T18:58:55+00:00 Alan Stern stern@rowland.harvard.edu 2019-10-01T17:39:47+00:00 3321ea12907abd477ff7e9bf5f365524b8f1f2fc This patch fixes a few minor typos and improves word usage in a few places in the Linux Kernel Memory Model's explanation.txt file. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
This patch fixes a few minor typos and improves word usage in a few
places in the Linux Kernel Memory Model's explanation.txt file.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model: Update the informal documentation 2019-08-09T17:28:57+00:00 Andrea Parri andrea.parri@amarulasolutions.com 2019-06-29T21:10:44+00:00 6738ff85c3ee8073d5b030cb26241d0009d4ce29 The formal memory consistency model has added support for plain accesses (and data races). While updating the informal documentation to describe this addition to the model is highly desirable and important future work, update the informal documentation to at least acknowledge such addition. Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: David Howells <dhowells@redhat.com> Cc: Jade Alglave <j.alglave@ucl.ac.uk> Cc: Luc Maranget <luc.maranget@inria.fr> Cc: "Paul E. McKenney" <paulmck@linux.ibm.com> Cc: Akira Yokosawa <akiyks@gmail.com> Cc: Daniel Lustig <dlustig@nvidia.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> 
The formal memory consistency model has added support for plain accesses
(and data races).  While updating the informal documentation to describe
this addition to the model is highly desirable and important future work,
update the informal documentation to at least acknowledge such addition.

Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: Akira Yokosawa <akiyks@gmail.com>
Cc: Daniel Lustig <dlustig@nvidia.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
tools/memory-model: Use cumul-fence instead of fence in ->prop example 2019-08-09T17:28:57+00:00 Joel Fernandes (Google) joel@joelfernandes.org 2019-07-29T12:36:05+00:00 6240973e5661a83df24e35a9a9c2013496931e2b To reduce ambiguity in the more exotic ->prop ordering example, this commit uses the term cumul-fence instead of the term fence for the two fences, so that the implict ->rfe on loads/stores to Y are covered by the description. Link: https://lore.kernel.org/lkml/20190729121745.GA140682@google.com Suggested-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> 
To reduce ambiguity in the more exotic ->prop ordering example, this
commit uses the term cumul-fence instead of the term fence for the two
fences, so that the implict ->rfe on loads/stores to Y are covered by
the description.

Link: https://lore.kernel.org/lkml/20190729121745.GA140682@google.com

Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>