11 Commits
| Author | SHA1 | Message | Date |
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Andrea Parri
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6738ff85c3 |
tools/memory-model: Update the informal documentation
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> |
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Andrea Parri
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034fb712a6 |
tools/memory-model: Avoid duplicating herdtools versions
Currently, herdtools version information appears no fewer than three times in the LKMM source, which is difficult to maintain. This commit therefore places the required version in one place, namely the tools/memory-model/README file. Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> |
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Paul E. McKenney
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ad9fd20b6d |
tools/memory-model: Update README for addition of SRCU
This commit updates the section on LKMM limitations to no longer say that SRCU is not modeled, but instead describe how LKMM's modeling of SRCU departs from the Linux-kernel implementation. TL;DR: There is no known valid use case that cares about the Linux kernel's ability to have partially overlapping SRCU read-side critical sections. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Andrea Parri <andrea.parri@amarulasolutions.com> |
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Paul E. McKenney
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b02eb5b096 |
tools/memory-model: Add scripts to check github litmus tests
The https://github.com/paulmckrcu/litmus repository contains a large number of C-language litmus tests that include "Result:" comments predicting the verification result. This commit adds a number of scripts that run tests on these litmus tests: checkghlitmus.sh: Runs all litmus tests in the https://github.com/paulmckrcu/litmus archive that are C-language and that have "Result:" comment lines documenting expected results, comparing the actual results to those expected. Clones the repository if it has not already been cloned into the "tools/memory-model/litmus" directory. initlitmushist.sh Run all litmus tests having no more than the specified number of processes given a specified timeout, recording the results in .litmus.out files. Clones the repository if it has not already been cloned into the "tools/memory-model/litmus" directory. newlitmushist.sh For all new or updated litmus tests having no more than the specified number of processes given a specified timeout, run and record the results in .litmus.out files. checklitmushist.sh Run all litmus tests having .litmus.out files from previous initlitmushist.sh or newlitmushist.sh runs, comparing the herd output to that of the original runs. The above scripts will run litmus tests concurrently, by default with one job per available CPU. Giving any of these scripts the --help argument will cause them to print usage information. This commit also adds a number of helper scripts that are not intended to be invoked from the command line: cmplitmushist.sh: Compare the output of two different runs of the same litmus test. judgelitmus.sh: Compare the output of a litmus test to its "Result:" comment line. parseargs.sh: Parse command-line arguments. runlitmushist.sh: Run the litmus tests whose pathnames are provided one per line on standard input. While in the area, this commit also makes the existing checklitmus.sh and checkalllitmus.sh scripts use parseargs.sh in order to provide a bit of uniformity. In addition, per-litmus-test status output is directed to stdout, while end-of-test summary information is directed to stderr. Finally, the error flag standardizes on "!!!" to assist those familiar with rcutorture output. The defaults for the parseargs.sh arguments may be overridden by using environment variables: LKMM_DESTDIR for --destdir, LKMM_HERD_OPTIONS for --herdoptions, LKMM_JOBS for --jobs, LKMM_PROCS for --procs, and LKMM_TIMEOUT for --timeout. [ paulmck: History-check summary-line changes per Alan Stern feedback. ] 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/20181203230451.28921-2-paulmck@linux.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Paul E. McKenney
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d8fa25c4ef |
tools/memory-model: Add more LKMM limitations
This commit adds more detail about compiler optimizations and not-yet-modeled Linux-kernel APIs. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Andrea Parri <andrea.parri@amarulasolutions.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> 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: 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/20180926182920.27644-4-paulmck@linux.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Andrea Parri
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71b7ff5ebc |
tools/memory-model: Rename litmus tests to comply to norm7
norm7 produces the 'normalized' name of a litmus test, when the test can be generated from a single cycle that passes through each process exactly once. The commit renames such tests in order to comply to the naming scheme implemented by this tool. Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Cc: Akira Yokosawa <akiyks@gmail.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: David Howells <dhowells@redhat.com> Cc: Jade Alglave <j.alglave@ucl.ac.uk> 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: 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/20180716180605.16115-14-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Akira Yokosawa
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5b62832c1e |
tools/memory-model: Update required version of herdtools7
Code generated by klitmus7 version 7.48 doesn't compile with kernel header of 4.15 and later due to the absence of ACCESS_ONCE(). As the issue has been resolved in herdtools7 7.49, bump the required version number in README. Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Andrea Parri <parri.andrea@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: David Howells <dhowells@redhat.com> Cc: Jade Alglave <j.alglave@ucl.ac.uk> 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: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Cc: linux-arch@vger.kernel.org Link: http://lkml.kernel.org/r/1526340837-12222-3-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Paul E. McKenney
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d095c12c53 |
tools/memory-model: Remove mention of docker/gentoo image
Because the docker and gentoo images haven't been updated in quite some time, they are likely to provide more confusion than help. This commit therefore removes mention of them from the README file. Reported-by: Alan Stern <stern@rowland.harvard.edu> 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: will.deacon@arm.com Link: http://lkml.kernel.org/r/1520443660-16858-2-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Paul E. McKenney
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8f7f2fbd00 |
tools/memory-model: Add required herd7 version to README file
LKMM and the herd7 tool are co-evolving, and out-of-date herd7 tools produce inaccurate results, often with no obvious error messages. This commit therefore adds the required herd7 version to the LKMM README file. Longer term, it would be good if .cat files could specify the required version in a manner allowing herd7 to produce clear diagnostics. Suggested-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: parri.andrea@gmail.com Cc: stern@rowland.harvard.edu Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1519169112-20593-9-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Andrea Parri
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48d44d4e8a |
tools/memory-model: Clarify the origin/scope of the tool name
Ingo pointed out that: "The "memory model" name is overly generic, ambiguous and somewhat misleading, as we usually mean the virtual memory layout/model when we say "memory model". GCC too uses it in that sense [...]" Make it clear that tools/memory-model/ uses the term "memory model" as shorthand for "memory consistency model" by calling out this convention in tools/memory-model/README. Stick to the original "memory model" term in sources' headers and for the subsystem name. Suggested-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Will Deacon <will.deacon@arm.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> 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: nborisov@suse.com Cc: npiggin@gmail.com Link: http://lkml.kernel.org/r/1519169112-20593-1-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Paul E. McKenney
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1c27b644c0 |
Automate memory-barriers.txt; provide Linux-kernel memory model
There is some reason to believe that Documentation/memory-barriers.txt could use some help, and a major purpose of this patch is to provide that help in the form of a design-time tool that can produce all valid executions of a small fragment of concurrent Linux-kernel code, which is called a "litmus test". This tool's functionality is roughly similar to a full state-space search. Please note that this is a design-time tool, not useful for regression testing. However, we hope that the underlying Linux-kernel memory model will be incorporated into other tools capable of analyzing large bodies of code for regression-testing purposes. The main tool is herd7, together with the linux-kernel.bell, linux-kernel.cat, linux-kernel.cfg, linux-kernel.def, and lock.cat files added by this patch. The herd7 executable takes the other files as input, and all of these files collectively define the Linux-kernel memory memory model. A brief description of each of these other files is provided in the README file. Although this tool does have its limitations, which are documented in the README file, it does improve on the version reported on in the LWN series (https://lwn.net/Articles/718628/ and https://lwn.net/Articles/720550/) by supporting locking and arithmetic, including a much wider variety of read-modify-write atomic operations. Please note that herd7 is not part of this submission, but is freely available from http://diy.inria.fr/sources/index.html (and via "git" at https://github.com/herd/herdtools7). A second tool is klitmus7, which converts litmus tests to loadable kernel modules for direct testing. As with herd7, the klitmus7 code is freely available from http://diy.inria.fr/sources/index.html (and via "git" at https://github.com/herd/herdtools7). Of course, litmus tests are not always the best way to fully understand a memory model, so this patch also includes Documentation/explanation.txt, which describes the memory model in detail. In addition, Documentation/recipes.txt provides example known-good and known-bad use cases for those who prefer working by example. This patch also includes a few sample litmus tests, and a great many more litmus tests are available at https://github.com/paulmckrcu/litmus. This patch was the result of a most excellent collaboration founded by Jade Alglave and also including Alan Stern, Andrea Parri, and Luc Maranget. For more details on the history of this collaboration, please refer to the Linux-kernel memory model presentations at 2016 LinuxCon EU, 2016 Kernel Summit, 2016 Linux Plumbers Conference, 2017 linux.conf.au, or 2017 Linux Plumbers Conference microconference. However, one aspect of the history does bear repeating due to weak copyright tracking earlier in this project, which extends back to early 2015. This weakness came to light in late 2017 after an LKMM presentation by Paul in which an audience member noted the similarity of some LKMM code to code in early published papers. This prompted a copyright review. From Alan Stern: To say that the model was mine is not entirely accurate. Pieces of it (especially the Scpv and Atomic axioms) were taken directly from Jade's models. And of course the Happens-before and Propagation relations and axioms were heavily based on Jade and Luc's work, even though they weren't identical to the earlier versions. Only the RCU portion was completely original. . . . One can make a much better case that I wrote the bulk of lock.cat. However, it was inspired by Luc's earlier version (and still shares some elements in common), and of course it benefited from feedback and testing from all members of our group. The model prior to Alan's was Luc Maranget's. From Luc: I totally agree on Alan Stern's account of the linux kernel model genesis. I thank him for his acknowledgments of my participation to previous model drafts. I'd like to complete Alan Stern's statement: any bell cat code I have written has its roots in discussions with Jade Alglave and Paul McKenney. Moreover I have borrowed cat and bell code written by Jade Alglave freely. This copyright review therefore resulted in late adds to the copyright statements of several files. Discussion of v1 has raised several issues, which we do not believe should block acceptance given that this level of change will be ongoing, just as it has been with memory-barriers.txt: o Under what conditions should ordering provided by pure locking be seen by CPUs not holding the relevant lock(s)? In particular, should the message-passing pattern be forbidden? o Should examples involving C11 release sequences be forbidden? Note that this C11 is still a moving target for this issue: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0735r0.html o Some details of the handling of internal dependencies for atomic read-modify-write atomic operations are still subject to debate. o Changes recently accepted into mainline greatly reduce the need to handle DEC Alpha as a special case. These changes add an smp_read_barrier_depends() to READ_ONCE(), thus causing Alpha to respect ordering of dependent reads. If these changes stick, the memory model can be simplified accordingly. o Will changes be required to accommodate RISC-V? Differences from v1: (http://lkml.kernel.org/r/20171113184031.GA26302@linux.vnet.ibm.com) o Add SPDX notations to .bell and .cat files, replacing textual license statements. o Add reference to upcoming ASPLOS paper to .bell and .cat files. o Updated identifier names in .bell and .cat files to match those used in the ASPLOS paper. o Updates to READMEs and other documentation based on review feedback. o Added a memory-ordering cheatsheet. o Update sigs to new Co-Developed-by and add acks and reviewed-bys. o Simplify rules detecting nested RCU read-side critical sections. o Update copyright statements as noted above. Co-Developed-by: Alan Stern <stern@rowland.harvard.edu> Co-Developed-by: Andrea Parri <parri.andrea@gmail.com> Co-Developed-by: Jade Alglave <j.alglave@ucl.ac.uk> Co-Developed-by: Luc Maranget <luc.maranget@inria.fr> Co-Developed-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Jade Alglave <j.alglave@ucl.ac.uk> Signed-off-by: Luc Maranget <luc.maranget@inria.fr> Signed-off-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Reviewed-by: Boqun Feng <boqun.feng@gmail.com> Acked-by: Will Deacon <will.deacon@arm.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Nicholas Piggin <npiggin@gmail.com> Acked-by: David Howells <dhowells@redhat.com> Acked-by: "Reshetova, Elena" <elena.reshetova@intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Akira Yokosawa <akiyks@gmail.com> Cc: <linux-arch@vger.kernel.org> |