linux.git/tools/memory-model/README, branch v6.6.132 Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git tools/memory-model/README: Update klitmus7 compat table 2022-05-03T17:12:48+00:00 Akira Yokosawa akiyks@gmail.com 2022-05-02T12:05:09+00:00 5b759db44195bb779828a188bad6b745c18dcd55 EXPORT_SYMBOL of do_exec() was removed in v5.17. Unfortunately, kernel modules from klitmus7 7.56 have do_exec() at the end of each kthread. herdtools7 7.56.1 has addressed the issue. Update the compatibility table accordingly. Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Cc: Luc Maranget <luc.maranget@inria.fr> Cc: Jade Alglave <j.alglave@ucl.ac.uk> Cc: stable@vger.kernel.org # v5.17+ Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
EXPORT_SYMBOL of do_exec() was removed in v5.17.  Unfortunately,
kernel modules from klitmus7 7.56 have do_exec() at the end of
each kthread.

herdtools7 7.56.1 has addressed the issue.

Update the compatibility table accordingly.

Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Luc Maranget <luc.maranget@inria.fr>
Cc: Jade Alglave <j.alglave@ucl.ac.uk>
Cc: stable@vger.kernel.org # v5.17+
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model: doc: Describe the requirement of the litmus-tests directory 2021-12-01T01:47:08+00:00 Boqun Feng boqun.feng@gmail.com 2021-10-25T14:54:15+00:00 b47c05ecf60bd8743ad8c0ee510d3e1c060529d7 It's better that we have some "standard" about which test should be put in the litmus-tests directory because it helps future contributors understand whether they should work on litmus-tests in kernel or Paul's GitHub repo. Therefore explain a little bit on what a "representative" litmus test is. Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
It's better that we have some "standard" about which test should be put
in the litmus-tests directory because it helps future contributors
understand whether they should work on litmus-tests in kernel or Paul's
GitHub repo. Therefore explain a little bit on what a "representative"
litmus test is.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model: Fix typo in klitmus7 compatibility table 2021-01-04T22:40:50+00:00 Akira Yokosawa akiyks@gmail.com 2020-11-28T05:32:15+00:00 3d5c70329b910ab583673a33e3a615873c5d4115 klitmus7 of herdtools7 7.48 or earlier depends on ACCESS_ONCE(), which was removed in Linux v4.15. Fix the obvious typo in the table. Fixes: d075a78a5ab1 ("tools/memory-model/README: Expand dependency of klitmus7") Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
klitmus7 of herdtools7 7.48 or earlier depends on ACCESS_ONCE(),
which was removed in Linux v4.15.
Fix the obvious typo in the table.

Fixes: d075a78a5ab1 ("tools/memory-model/README: Expand dependency of klitmus7")
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model: Move Documentation description to Documentation/README 2020-10-26T23:18:53+00:00 Paul E. McKenney paulmck@kernel.org 2020-08-04T21:00:17+00:00 ab8bcad67bee82e4be290b32f0faaf582d7c3edc This commit moves the descriptions of the files residing in tools/memory-model/Documentation to a README file in that directory, leaving behind the description of tools/memory-model/Documentation/README itself. After this change, tools/memory-model/Documentation/README provides a guide to the files in the tools/memory-model/Documentation directory, guiding people with different skills and needs to the most appropriate starting point. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
This commit moves the descriptions of the files residing in
tools/memory-model/Documentation to a README file in that directory,
leaving behind the description of tools/memory-model/Documentation/README
itself.  After this change, tools/memory-model/Documentation/README
provides a guide to the files in the tools/memory-model/Documentation
directory, guiding people with different skills and needs to the most
appropriate starting point.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model: Add a simple entry point document 2020-09-03T16:51:01+00:00 Paul E. McKenney paulmck@kernel.org 2020-08-04T17:58:55+00:00 0b8c06b75ea143f3c68aa419c36e82d9ab7454f8 Current LKMM documentation assumes that the reader already understands concurrency in the Linux kernel, which won't necessarily always be the case. This commit supplies a simple.txt file that provides a starting point for someone who is new to concurrency in the Linux kernel. That said, this file might also useful as a reminder to experienced developers of simpler approaches to dealing with concurrency. Link: Link: https://lwn.net/Articles/827180/ [ paulmck: Apply feedback from Joel Fernandes. ] Co-developed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Dave Chinner <dchinner@redhat.com> Co-developed-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
Current LKMM documentation assumes that the reader already understands
concurrency in the Linux kernel, which won't necessarily always be the
case.  This commit supplies a simple.txt file that provides a starting
point for someone who is new to concurrency in the Linux kernel.
That said, this file might also useful as a reminder to experienced
developers of simpler approaches to dealing with concurrency.

Link: Link: https://lwn.net/Articles/827180/
[ paulmck: Apply feedback from Joel Fernandes. ]
Co-developed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Co-developed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model: Improve litmus-test documentation 2020-09-03T16:51:01+00:00 Paul E. McKenney paulmck@kernel.org 2020-08-04T00:19:54+00:00 984f272be9d7b2dd8b17e35d437e5da500b502ae The current LKMM documentation says very little about litmus tests, and worse yet directs people to the herd7 documentation for more information. Now, the herd7 documentation is quite voluminous and educational, but it is intended for people creating and modifying memory models, not those attempting to use them. This commit therefore updates README and creates a litmus-tests.txt file that gives an overview of litmus-test format and describes ways of modeling various special cases, illustrated with numerous examples. [ paulmck: Add Alan Stern feedback. ] [ paulmck: Apply Dave Chinner feedback. ] [ paulmck: Apply Andrii Nakryiko feedback. ] [ paulmck: Apply Johannes Weiner feedback. ] Link: https://lwn.net/Articles/827180/ Reported-by: Dave Chinner <david@fromorbit.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
The current LKMM documentation says very little about litmus tests, and
worse yet directs people to the herd7 documentation for more information.
Now, the herd7 documentation is quite voluminous and educational,
but it is intended for people creating and modifying memory models,
not those attempting to use them.

This commit therefore updates README and creates a litmus-tests.txt
file that gives an overview of litmus-test format and describes ways of
modeling various special cases, illustrated with numerous examples.

[ paulmck: Add Alan Stern feedback. ]
[ paulmck: Apply Dave Chinner feedback. ]
[ paulmck: Apply Andrii Nakryiko feedback. ]
[ paulmck: Apply Johannes Weiner feedback. ]
Link: https://lwn.net/Articles/827180/
Reported-by: Dave Chinner <david@fromorbit.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model/README: Mention herdtools7 7.56 in compatibility table 2020-06-29T19:05:18+00:00 Akira Yokosawa akiyks@gmail.com 2020-06-23T21:56:43+00:00 2bfa5c62debe43e3779e03bfc66b75ab72098db1 herdtools7 7.56 is going to be released in the week of 22 Jun 2020. This commit therefore adds the exact version in the compatibility table. Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
herdtools7 7.56 is going to be released in the week of 22 Jun 2020.
This commit therefore adds the exact version in the compatibility table.

Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model/README: Expand dependency of klitmus7 2020-06-29T19:05:18+00:00 Akira Yokosawa akiyks@gmail.com 2020-05-31T11:04:32+00:00 d075a78a5ab19389d5600923d6ad5391d7cd1be8 klitmus7 is independent of the memory model but depends on the build-target kernel release. It occasionally lost compatibility due to kernel API changes [1, 2, 3]. It was remedied in a backwards-compatible manner respectively [4, 5, 6]. Reflect this fact in README. [1]: b899a850431e ("compiler.h: Remove ACCESS_ONCE()") [2]: 0bb95f80a38f ("Makefile: Globally enable VLA warning") [3]: d56c0d45f0e2 ("proc: decouple proc from VFS with "struct proc_ops"") [4]: https://github.com/herd/herdtools7/commit/e87d7f9287d1 ("klitmus: Use WRITE_ONCE and READ_ONCE in place of deprecated ACCESS_ONCE") [5]: https://github.com/herd/herdtools7/commit/a0cbb10d02be ("klitmus: Avoid variable length array") [6]: https://github.com/herd/herdtools7/commit/46b9412d3a58 ("klitmus: Linux kernel v5.6.x compat") NOTE: [5] was ahead of herdtools7 7.53, which did not make an official release. Code generated by klitmus7 without [5] can still be built targeting Linux 4.20--5.5 if you don't care VLA warnings. Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
klitmus7 is independent of the memory model but depends on the
build-target kernel release.
It occasionally lost compatibility due to kernel API changes [1, 2, 3].
It was remedied in a backwards-compatible manner respectively [4, 5, 6].

Reflect this fact in README.

[1]: b899a850431e ("compiler.h: Remove ACCESS_ONCE()")
[2]: 0bb95f80a38f ("Makefile: Globally enable VLA warning")
[3]: d56c0d45f0e2 ("proc: decouple proc from VFS with "struct proc_ops"")
[4]: https://github.com/herd/herdtools7/commit/e87d7f9287d1
     ("klitmus: Use WRITE_ONCE and READ_ONCE in place of deprecated ACCESS_ONCE")
[5]: https://github.com/herd/herdtools7/commit/a0cbb10d02be
     ("klitmus: Avoid variable length array")
[6]: https://github.com/herd/herdtools7/commit/46b9412d3a58
     ("klitmus: Linux kernel v5.6.x compat")

NOTE: [5] was ahead of herdtools7 7.53, which did not make an
official release.  Code generated by klitmus7 without [5] can still be
built targeting Linux 4.20--5.5 if you don't care VLA warnings.

Acked-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
tools/memory-model: Add an exception for limitations on _unless() family 2020-06-29T19:05:18+00:00 Boqun Feng boqun.feng@gmail.com 2020-03-26T02:40:19+00:00 4a9cc65f7a715ba1f4f58529f7bf6f1548d8701f According to Luc, atomic_add_unless() is directly provided by herd7, therefore it can be used in litmus tests. So change the limitation section in README to unlimit the use of atomic_add_unless(). Cc: Luc Maranget <luc.maranget@inria.fr> Acked-by: Andrea Parri <parri.andrea@gmail.com> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
According to Luc, atomic_add_unless() is directly provided by herd7,
therefore it can be used in litmus tests. So change the limitation
section in README to unlimit the use of atomic_add_unless().

Cc: Luc Maranget <luc.maranget@inria.fr>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Boqun Feng <boqun.feng@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>