On Fri, Nov 17, 2017 at 07:27:46PM +0800, Boqun Feng wrote: > On Wed, Nov 15, 2017 at 08:37:49AM -0800, Paul E. McKenney wrote: > > On Tue, Nov 14, 2017 at 09:15:05AM -0800, Paul E. McKenney wrote: > > > On Tue, Nov 14, 2017 at 10:19:21AM -0500, Alan Stern wrote: > > > > On Tue, 14 Nov 2017, Peter Zijlstra wrote: > > > > > > > > > On Mon, Nov 13, 2017 at 10:40:31AM -0800, Paul E. McKenney wrote: > > > > > > commit 82a1431549b4eae531e83298fd72cd0acea08540 > > > > > > Author: Paul E. McKenney <paul...@linux.vnet.ibm.com> > > > > > > Date: Mon Nov 13 10:30:07 2017 -0800 > > > > > > > > > > > > tools: 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. > > > > > > > > > > > > Signed-off-by: Alan Stern <st...@rowland.harvard.edu> > > > > > > Signed-off-by: Andrea Parri <parri.and...@gmail.com> > > > > > > Signed-off-by: Will Deacon <will.dea...@arm.com> > > > > > > Signed-off-by: Peter Zijlstra <pet...@infradead.org> > > > > > > Signed-off-by: Boqun Feng <boqun.f...@gmail.com> > > > > > > Signed-off-by: Nicholas Piggin <npig...@gmail.com> > > > > > > Signed-off-by: David Howells <dhowe...@redhat.com> > > > > > > Signed-off-by: Jade Alglave <j.algl...@ucl.ac.uk> > > > > > > Signed-off-by: Luc Maranget <luc.maran...@inria.fr> > > > > > > Signed-off-by: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> > > > > > > Cc: <linux-a...@vger.kernel.org> > > > > > > > > > > So I think that SoB chains like that are utter crap. I think you meant > > > > > to have all but the one from you be an Ack or similar. > > > > > > > > That's right. Git doesn't understand the concept of multiple > > > > authorship. Accepted practice is to have one Signed-off-by line and a > > > > bunch of Acked-by or Reviewed-by tags. > > > > > > > > When there's a chain of Signed-off-by tags, it means the first person > > > > was the author, who submitted it to the second person's tree, and it > > > > went from there to the third person's tree, etc. (which would imply > > > > multiple levels of maintainers and submaintainers). > > > > > > I could add a paragraph just before the Signed-off-by/Acked-by/etc. > > > block describing the roles and contributions, convert the people who > > > were directly involved to Reviewed-by and everyone else to Acked-by > > > (unless they explicitly provided a Reviewed-by). > > > > > > Would that work, or does someone have a better approach? > > > > How about using the shiny new "Co-Developed-by"? > > https://marc.info/?l=linux-kernel&m=151083859723653&w=2
This seems to be exactly what we were looking for/we needed. Altought still undocumented in "mainline", the tag has already found some uses in the past, and it appears in its commit log. I've just modified com- mit-log.txt in the "memory-model" repo. to adopt this tag. > > Besides, as you know, I've been following and learning a lot from this > model from maybe very beginning, and I have read throught the documents > and cat files, and even got a chance to verify some RCU-involved code > with Andrea using this model ;-) So feel free to add: > > Reviewed-by: Boqun Feng <boqun.f...@gmail.com> Added. Thanks, Andrea > > Regards, > Boqun > > > Hearing no objections, here is an updated prototype patch. Thank you > > all for the review, comments, and updates! > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > commit 869b3c396eb908e3dfafbd75ed33421b3bcd50bf > > Author: Paul E. McKenney <paul...@linux.vnet.ibm.com> > > Date: Mon Nov 13 10:30:07 2017 -0800 > > > > tools: 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. > > > > Reviewed-by: Alan Stern <st...@rowland.harvard.edu> > > Reviewed-by: Andrea Parri <parri.and...@gmail.com> > > Reviewed-by: Jade Alglave <j.algl...@ucl.ac.uk> > > Reviewed-by: Luc Maranget <luc.maran...@inria.fr> > > Signed-off-by: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> > > Acked-by: Will Deacon <will.dea...@arm.com> > > Acked-by: Peter Zijlstra <pet...@infradead.org> > > Acked-by: Boqun Feng <boqun.f...@gmail.com> > > Acked-by: Nicholas Piggin <npig...@gmail.com> > > Acked-by: David Howells <dhowe...@redhat.com> > > Acked-by: "Reshetova, Elena" <elena.reshet...@intel.com> > > Cc: <linux-a...@vger.kernel.org> > > > [...]
