mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-21 10:05:00 +08:00
5b759db441
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>
224 lines
7.2 KiB
Plaintext
224 lines
7.2 KiB
Plaintext
=====================================
|
|
LINUX KERNEL MEMORY CONSISTENCY MODEL
|
|
=====================================
|
|
|
|
============
|
|
INTRODUCTION
|
|
============
|
|
|
|
This directory contains the memory consistency model (memory model, for
|
|
short) of the Linux kernel, written in the "cat" language and executable
|
|
by the externally provided "herd7" simulator, which exhaustively explores
|
|
the state space of small litmus tests.
|
|
|
|
In addition, the "klitmus7" tool (also externally provided) may be used
|
|
to convert a litmus test to a Linux kernel module, which in turn allows
|
|
that litmus test to be exercised within the Linux kernel.
|
|
|
|
|
|
============
|
|
REQUIREMENTS
|
|
============
|
|
|
|
Version 7.52 or higher of the "herd7" and "klitmus7" tools must be
|
|
downloaded separately:
|
|
|
|
https://github.com/herd/herdtools7
|
|
|
|
See "herdtools7/INSTALL.md" for installation instructions.
|
|
|
|
Note that although these tools usually provide backwards compatibility,
|
|
this is not absolutely guaranteed.
|
|
|
|
For example, a future version of herd7 might not work with the model
|
|
in this release. A compatible model will likely be made available in
|
|
a later release of Linux kernel.
|
|
|
|
If you absolutely need to run the model in this particular release,
|
|
please try using the exact version called out above.
|
|
|
|
klitmus7 is independent of the model provided here. It has its own
|
|
dependency on a target kernel release where converted code is built
|
|
and executed. Any change in kernel APIs essential to klitmus7 will
|
|
necessitate an upgrade of klitmus7.
|
|
|
|
If you find any compatibility issues in klitmus7, please inform the
|
|
memory model maintainers.
|
|
|
|
klitmus7 Compatibility Table
|
|
----------------------------
|
|
|
|
============ ==========
|
|
target Linux herdtools7
|
|
------------ ----------
|
|
-- 4.14 7.48 --
|
|
4.15 -- 4.19 7.49 --
|
|
4.20 -- 5.5 7.54 --
|
|
5.6 -- 5.16 7.56 --
|
|
5.17 -- 7.56.1 --
|
|
============ ==========
|
|
|
|
|
|
==================
|
|
BASIC USAGE: HERD7
|
|
==================
|
|
|
|
The memory model is used, in conjunction with "herd7", to exhaustively
|
|
explore the state space of small litmus tests. Documentation describing
|
|
the format, features, capabilities and limitations of these litmus
|
|
tests is available in tools/memory-model/Documentation/litmus-tests.txt.
|
|
|
|
Example litmus tests may be found in the Linux-kernel source tree:
|
|
|
|
tools/memory-model/litmus-tests/
|
|
Documentation/litmus-tests/
|
|
|
|
Several thousand more example litmus tests are available here:
|
|
|
|
https://github.com/paulmckrcu/litmus
|
|
https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/perfbook.git/tree/CodeSamples/formal/herd
|
|
https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/perfbook.git/tree/CodeSamples/formal/litmus
|
|
|
|
Documentation describing litmus tests and now to use them may be found
|
|
here:
|
|
|
|
tools/memory-model/Documentation/litmus-tests.txt
|
|
|
|
The remainder of this section uses the SB+fencembonceonces.litmus test
|
|
located in the tools/memory-model directory.
|
|
|
|
To run SB+fencembonceonces.litmus against the memory model:
|
|
|
|
$ cd $LINUX_SOURCE_TREE/tools/memory-model
|
|
$ herd7 -conf linux-kernel.cfg litmus-tests/SB+fencembonceonces.litmus
|
|
|
|
Here is the corresponding output:
|
|
|
|
Test SB+fencembonceonces Allowed
|
|
States 3
|
|
0:r0=0; 1:r0=1;
|
|
0:r0=1; 1:r0=0;
|
|
0:r0=1; 1:r0=1;
|
|
No
|
|
Witnesses
|
|
Positive: 0 Negative: 3
|
|
Condition exists (0:r0=0 /\ 1:r0=0)
|
|
Observation SB+fencembonceonces Never 0 3
|
|
Time SB+fencembonceonces 0.01
|
|
Hash=d66d99523e2cac6b06e66f4c995ebb48
|
|
|
|
The "Positive: 0 Negative: 3" and the "Never 0 3" each indicate that
|
|
this litmus test's "exists" clause can not be satisfied.
|
|
|
|
See "herd7 -help" or "herdtools7/doc/" for more information on running the
|
|
tool itself, but please be aware that this documentation is intended for
|
|
people who work on the memory model itself, that is, people making changes
|
|
to the tools/memory-model/linux-kernel.* files. It is not intended for
|
|
people focusing on writing, understanding, and running LKMM litmus tests.
|
|
|
|
|
|
=====================
|
|
BASIC USAGE: KLITMUS7
|
|
=====================
|
|
|
|
The "klitmus7" tool converts a litmus test into a Linux kernel module,
|
|
which may then be loaded and run.
|
|
|
|
For example, to run SB+fencembonceonces.litmus against hardware:
|
|
|
|
$ mkdir mymodules
|
|
$ klitmus7 -o mymodules litmus-tests/SB+fencembonceonces.litmus
|
|
$ cd mymodules ; make
|
|
$ sudo sh run.sh
|
|
|
|
The corresponding output includes:
|
|
|
|
Test SB+fencembonceonces Allowed
|
|
Histogram (3 states)
|
|
644580 :>0:r0=1; 1:r0=0;
|
|
644328 :>0:r0=0; 1:r0=1;
|
|
711092 :>0:r0=1; 1:r0=1;
|
|
No
|
|
Witnesses
|
|
Positive: 0, Negative: 2000000
|
|
Condition exists (0:r0=0 /\ 1:r0=0) is NOT validated
|
|
Hash=d66d99523e2cac6b06e66f4c995ebb48
|
|
Observation SB+fencembonceonces Never 0 2000000
|
|
Time SB+fencembonceonces 0.16
|
|
|
|
The "Positive: 0 Negative: 2000000" and the "Never 0 2000000" indicate
|
|
that during two million trials, the state specified in this litmus
|
|
test's "exists" clause was not reached.
|
|
|
|
And, as with "herd7", please see "klitmus7 -help" or "herdtools7/doc/"
|
|
for more information. And again, please be aware that this documentation
|
|
is intended for people who work on the memory model itself, that is,
|
|
people making changes to the tools/memory-model/linux-kernel.* files.
|
|
It is not intended for people focusing on writing, understanding, and
|
|
running LKMM litmus tests.
|
|
|
|
|
|
====================
|
|
DESCRIPTION OF FILES
|
|
====================
|
|
|
|
Documentation/README
|
|
Guide to the other documents in the Documentation/ directory.
|
|
|
|
linux-kernel.bell
|
|
Categorizes the relevant instructions, including memory
|
|
references, memory barriers, atomic read-modify-write operations,
|
|
lock acquisition/release, and RCU operations.
|
|
|
|
More formally, this file (1) lists the subtypes of the various
|
|
event types used by the memory model and (2) performs RCU
|
|
read-side critical section nesting analysis.
|
|
|
|
linux-kernel.cat
|
|
Specifies what reorderings are forbidden by memory references,
|
|
memory barriers, atomic read-modify-write operations, and RCU.
|
|
|
|
More formally, this file specifies what executions are forbidden
|
|
by the memory model. Allowed executions are those which
|
|
satisfy the model's "coherence", "atomic", "happens-before",
|
|
"propagation", and "rcu" axioms, which are defined in the file.
|
|
|
|
linux-kernel.cfg
|
|
Convenience file that gathers the common-case herd7 command-line
|
|
arguments.
|
|
|
|
linux-kernel.def
|
|
Maps from C-like syntax to herd7's internal litmus-test
|
|
instruction-set architecture.
|
|
|
|
litmus-tests
|
|
Directory containing a few representative litmus tests, which
|
|
are listed in litmus-tests/README. A great deal more litmus
|
|
tests are available at https://github.com/paulmckrcu/litmus.
|
|
|
|
By "representative", it means the one in the litmus-tests
|
|
directory is:
|
|
|
|
1) simple, the number of threads should be relatively
|
|
small and each thread function should be relatively
|
|
simple.
|
|
2) orthogonal, there should be no two litmus tests
|
|
describing the same aspect of the memory model.
|
|
3) textbook, developers can easily copy-paste-modify
|
|
the litmus tests to use the patterns on their own
|
|
code.
|
|
|
|
lock.cat
|
|
Provides a front-end analysis of lock acquisition and release,
|
|
for example, associating a lock acquisition with the preceding
|
|
and following releases and checking for self-deadlock.
|
|
|
|
More formally, this file defines a performance-enhanced scheme
|
|
for generation of the possible reads-from and coherence order
|
|
relations on the locking primitives.
|
|
|
|
README
|
|
This file.
|
|
|
|
scripts Various scripts, see scripts/README.
|