Hi Paul,
thanks to you and all the involved guys for this useful tool.

I give it a try today and found that by installing herd7 by just
following the instruction in herdtools7/INSTALL.md, and precisely
installing it via:

opam install herdtools7

it seems to give you a tool which fails to run the basic example in
your README with this error:

File "./linux-kernel.def", line 44, characters 29-30: unexpected '-' (in macros)

As suggested by Will, by building instead herd7 HEAD (commit 44d69c2)
everything works fine.

Maybe it's a know issue, in case just ignore me. :)

Otherwise, maybe it can be worth to add to the README a note on which
minimum version of the herd7 tool is required.

opma version (not working) : 7.47, Rev: exported
master version (working for me) : 7.47+7(dev), Rev: 44d69c2b1b5ca0f97bd138899d31532ee5e4e084

Cheers Patrick

On 25-Jan 01:34, Paul E. McKenney wrote:
> Hello, Ingo,
>
> This pull request contains a single commit that adds a memory model to
> the tools directory. This memory model can (roughly speaking) be thought
> of as an automated version of memory-barriers.txt. It is written in the
> "cat" language, which is executable by the externally provided "herd7"
> simulator, which exhaustively explores the state space of small litmus
> tests.
>
> This memory model is accompanied by extensive documentation on its use
> and its design. Two versions have been sent to LKML and feedback
> incorporated:
>
> 1. http://lkml.kernel.org/r/[email protected]
> 2. http://lkml.kernel.org/r/[email protected]
>
> This model has been presented and demoed at a number of Linux gatherings,
> including the 2016 LinuxCon EU, the 2016 Linux Plumbers Conference,
> the 2016 Linux Kernel Summit, the 2017 linux.conf.au, and the 2017 Linux
> Plumbers Conference, which featured a workshop helping a number of Linux
> kernel hackers install and use the tool.
>
> This memory model has matured to the point where it would be good to include
> it in the Linux kernel, for example, to allow it to track changes as new
> hardware and use cases are added. We expect the rate of change to be similar
> to that of Documentation/memory-barriers.txt.
>
> This memory model is available in the git repository at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
>
> for you to fetch changes up to 1c27b644c0fdbc61e113b8faee14baeb8df32486:
>
> Automate memory-barriers.txt; provide Linux-kernel memory model (2018-01-24 20:53:49 -0800)
>
> ----------------------------------------------------------------
> Paul E. McKenney (1):
> Automate memory-barriers.txt; provide Linux-kernel memory model
>
> tools/memory-model/Documentation/cheatsheet.txt | 30 +
> tools/memory-model/Documentation/explanation.txt | 1840 ++++++++++++++++++++
> tools/memory-model/Documentation/recipes.txt | 570 ++++++
> tools/memory-model/Documentation/references.txt | 107 ++
> tools/memory-model/MAINTAINERS | 15 +
> tools/memory-model/README | 220 +++
> tools/memory-model/linux-kernel.bell | 53 +
> tools/memory-model/linux-kernel.cat | 124 ++
> tools/memory-model/linux-kernel.cfg | 21 +
> tools/memory-model/linux-kernel.def | 108 ++
> .../litmus-tests/CoRR+poonceonce+Once.litmus | 19 +
> .../litmus-tests/CoRW+poonceonce+Once.litmus | 18 +
> .../litmus-tests/CoWR+poonceonce+Once.litmus | 18 +
> .../litmus-tests/CoWW+poonceonce.litmus | 11 +
> .../litmus-tests/IRIW+mbonceonces+OnceOnce.litmus | 35 +
> .../litmus-tests/IRIW+poonceonces+OnceOnce.litmus | 33 +
> .../litmus-tests/ISA2+poonceonces.litmus | 28 +
> ...cerelease+poacquirerelease+poacquireonce.litmus | 28 +
> .../litmus-tests/LB+ctrlonceonce+mbonceonce.litmus | 23 +
> .../LB+poacquireonce+pooncerelease.litmus | 21 +
> .../litmus-tests/LB+poonceonces.litmus | 21 +
> .../litmus-tests/MP+onceassign+derefonce.litmus | 25 +
> tools/memory-model/litmus-tests/MP+polocks.litmus | 24 +
> .../litmus-tests/MP+poonceonces.litmus | 20 +
> .../MP+pooncerelease+poacquireonce.litmus | 20 +
> .../memory-model/litmus-tests/MP+porevlocks.litmus | 24 +
> .../litmus-tests/MP+wmbonceonce+rmbonceonce.litmus | 22 +
> .../memory-model/litmus-tests/R+mbonceonces.litmus | 21 +
> .../memory-model/litmus-tests/R+poonceonces.litmus | 19 +
> tools/memory-model/litmus-tests/README | 125 ++
> .../memory-model/litmus-tests/S+poonceonces.litmus | 19 +
> .../S+wmbonceonce+poacquireonce.litmus | 20 +
> .../litmus-tests/SB+mbonceonces.litmus | 23 +
> .../litmus-tests/SB+poonceonces.litmus | 21 +
> .../litmus-tests/WRC+poonceonces+Once.litmus | 27 +
> .../WRC+pooncerelease+rmbonceonce+Once.litmus | 28 +
> .../Z6.0+pooncelock+poonceLock+pombonce.litmus | 33 +
> .../Z6.0+pooncelock+pooncelock+pombonce.litmus | 32 +
> ...ooncerelease+poacquirerelease+mbonceonce.litmus | 28 +
> tools/memory-model/lock.cat | 99 ++
> 40 files changed, 3973 insertions(+)
> create mode 100644 tools/memory-model/Documentation/cheatsheet.txt
> create mode 100644 tools/memory-model/Documentation/explanation.txt
> create mode 100644 tools/memory-model/Documentation/recipes.txt
> create mode 100644 tools/memory-model/Documentation/references.txt
> create mode 100644 tools/memory-model/MAINTAINERS
> create mode 100644 tools/memory-model/README
> create mode 100644 tools/memory-model/linux-kernel.bell
> create mode 100644 tools/memory-model/linux-kernel.cat
> create mode 100644 tools/memory-model/linux-kernel.cfg
> create mode 100644 tools/memory-model/linux-kernel.def
> create mode 100644 tools/memory-model/litmus-tests/CoRR+poonceonce+Once.litmus
> create mode 100644 tools/memory-model/litmus-tests/CoRW+poonceonce+Once.litmus
> create mode 100644 tools/memory-model/litmus-tests/CoWR+poonceonce+Once.litmus
> create mode 100644 tools/memory-model/litmus-tests/CoWW+poonceonce.litmus
> create mode 100644 tools/memory-model/litmus-tests/IRIW+mbonceonces+OnceOnce.litmus
> create mode 100644 tools/memory-model/litmus-tests/IRIW+poonceonces+OnceOnce.litmus
> create mode 100644 tools/memory-model/litmus-tests/ISA2+poonceonces.litmus
> create mode 100644 tools/memory-model/litmus-tests/ISA2+pooncerelease+poacquirerelease+poacquireonce.litmus
> create mode 100644 tools/memory-model/litmus-tests/LB+ctrlonceonce+mbonceonce.litmus
> create mode 100644 tools/memory-model/litmus-tests/LB+poacquireonce+pooncerelease.litmus
> create mode 100644 tools/memory-model/litmus-tests/LB+poonceonces.litmus
> create mode 100644 tools/memory-model/litmus-tests/MP+onceassign+derefonce.litmus
> create mode 100644 tools/memory-model/litmus-tests/MP+polocks.litmus
> create mode 100644 tools/memory-model/litmus-tests/MP+poonceonces.litmus
> create mode 100644 tools/memory-model/litmus-tests/MP+pooncerelease+poacquireonce.litmus
> create mode 100644 tools/memory-model/litmus-tests/MP+porevlocks.litmus
> create mode 100644 tools/memory-model/litmus-tests/MP+wmbonceonce+rmbonceonce.litmus
> create mode 100644 tools/memory-model/litmus-tests/R+mbonceonces.litmus
> create mode 100644 tools/memory-model/litmus-tests/R+poonceonces.litmus
> create mode 100644 tools/memory-model/litmus-tests/README
> create mode 100644 tools/memory-model/litmus-tests/S+poonceonces.litmus
> create mode 100644 tools/memory-model/litmus-tests/S+wmbonceonce+poacquireonce.litmus
> create mode 100644 tools/memory-model/litmus-tests/SB+mbonceonces.litmus
> create mode 100644 tools/memory-model/litmus-tests/SB+poonceonces.litmus
> create mode 100644 tools/memory-model/litmus-tests/WRC+poonceonces+Once.litmus
> create mode 100644 tools/memory-model/litmus-tests/WRC+pooncerelease+rmbonceonce+Once.litmus
> create mode 100644 tools/memory-model/litmus-tests/Z6.0+pooncelock+poonceLock+pombonce.litmus
> create mode 100644 tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus
> create mode 100644 tools/memory-model/litmus-tests/Z6.0+pooncerelease+poacquirerelease+mbonceonce.litmus
> create mode 100644 tools/memory-model/lock.cat
>

--
#include <best/regards.h>

Patrick Bellasi

2018-02-08 20:05:27

by Peter Zijlstra

[permalink] [raw]

On Fri, Feb 09, 2018 at 01:41:12PM +0100, Andrea Parri wrote:
> On Fri, Feb 09, 2018 at 03:29:37AM -0800, Paul E. McKenney wrote:
> > On Fri, Feb 09, 2018 at 10:11:10AM +0100, Andrea Parri wrote:
> > > On Thu, Feb 08, 2018 at 09:02:19PM +0100, Peter Zijlstra wrote:
> > > > On Thu, Feb 08, 2018 at 06:41:06PM +0000, Patrick Bellasi wrote:
> > > > > Hi Paul,
> > > > > thanks to you and all the involved guys for this useful tool.
> > > > >
> > > > > I give it a try today and found that by installing herd7 by just
> > > > > following the instruction in herdtools7/INSTALL.md, and precisely
> > > > > installing it via:
> > > > >
> > > > > opam install herdtools7
> > > > >
> > > > > it seems to give you a tool which fails to run the basic example in
> > > > > your README with this error:
> > > > >
> > > > > File "./linux-kernel.def", line 44, characters 29-30: unexpected '-' (in macros)
> > > > >
> > > > > As suggested by Will, by building instead herd7 HEAD (commit 44d69c2)
> > > > > everything works fine.
> > > > >
> > > > > Maybe it's a know issue, in case just ignore me. :)
> > > > >
> > > > > Otherwise, maybe it can be worth to add to the README a note on which
> > > > > minimum version of the herd7 tool is required.
> > > > >
> > > > > opma version (not working) : 7.47, Rev: exported
> > > > > master version (working for me) : 7.47+7(dev), Rev: 44d69c2b1b5ca0f97bd138899d31532ee5e4e084
> > > >
> > > > Urgh. So that's why it wouldn't work.
> > > >
> > > > I remember Paul saying you needed the latest version, which is why I
> > > > rebuild from opam, but building top of git is a bit much.
> > >
> > > +1
> > >
> > > _Sadly_ enough, co-developers and I were aware of this issue,
> > > but it was only mildly reported here (c.f.,
> > >
> > > https://marc.info/?l=linux-kernel&m=151638196427685&w=2 ).
> > >
> > > This bisects to that (crazy):
> > >
> > > 2d5fba7782d669c6a1cc577dbc3bf507780273bb
> > > ("linux-kernel*: Make RCU identifiers match ASPLOS paper")
> > >
> > > From repo.: https://github.com/aparri/memory-model
> > >
> > > which not only did break 7.47, but also made the bell uglier
> > > by mixing dashes and underscores in a very same block.
> > >
> > > As a solution to this issue, I can envisage a partial revert
> > > of that commit (just replace those dashes); Paul, Jade, Luc:
> > > any better solution?
> > >
> > > (Sorry for being late on IRC, glad this came out here,)
> >
> > Or maybe a 7.48 release?
>
> This would work, _prior upgrade. (This's not my call of course).
>
> I do however want to iterate, looking again at the above commit:
>
> 'rb_dep (*smp_read_barrier_depends*) ||
> - 'rcu_read_lock (*rcu_read_lock*) ||
> - 'rcu_read_unlock (*rcu_read_unlock*) ||
> - 'sync (*synchronize_rcu*) ||
> + 'rcu-lock (*rcu_read_lock*) ||
> + 'rcu-unlock (*rcu_read_unlock*) ||
> + 'sync-rcu (*synchronize_rcu*) ||
> 'before_atomic (*smp_mb__before_atomic*) ||
> 'after_atomic (*smp_mb__after_atomic*) ||
> 'after_spinlock (*smp_mb__after_spinlock*)
>
> The question arises: dash or underscore? This needs to be fixed.

The underscore in rb_dep is determined by herd, so the best shot there
is to update the model based on the de-Alpha-ication of the kernel,
thus (I believe) allowing rb_dep to be removed entirely, along with
its underscore.

As far as I know, there is nothing preventing removing underscores
from before_atomic, after_atomic, and after_spinlock, and the diff
below seems to work OK. And I did have to make a litmus test for
smp_mb__before_atomic() and smp_mb__after_atomic(). ;-)

Thoughts?

Thanx, Paul

------------------------------------------------------------------------

diff --git a/tools/memory-model/linux-kernel.bell b/tools/memory-model/linux-kernel.bell
index b984bbda01a5..18885ad15de9 100644
--- a/tools/memory-model/linux-kernel.bell
+++ b/tools/memory-model/linux-kernel.bell
@@ -28,9 +28,9 @@ enum Barriers = 'wmb (*smp_wmb*) ||
'rcu-lock (*rcu_read_lock*) ||
'rcu-unlock (*rcu_read_unlock*) ||
'sync-rcu (*synchronize_rcu*) ||
- 'before_atomic (*smp_mb__before_atomic*) ||
- 'after_atomic (*smp_mb__after_atomic*) ||
- 'after_spinlock (*smp_mb__after_spinlock*)
+ 'before-atomic (*smp_mb__before_atomic*) ||
+ 'after-atomic (*smp_mb__after_atomic*) ||
+ 'after-spinlock (*smp_mb__after_spinlock*)
instructions F[Barriers]

(* Compute matching pairs of nested Rcu-lock and Rcu-unlock *)
diff --git a/tools/memory-model/linux-kernel.cat b/tools/memory-model/linux-kernel.cat
index babe2b3b0bb3..f0d27f813ec2 100644
--- a/tools/memory-model/linux-kernel.cat
+++ b/tools/memory-model/linux-kernel.cat
@@ -29,9 +29,9 @@ let rb-dep = [R] ; fencerel(Rb_dep) ; [R]
let rmb = [R \ Noreturn] ; fencerel(Rmb) ; [R \ Noreturn]
let wmb = [W] ; fencerel(Wmb) ; [W]
let mb = ([M] ; fencerel(Mb) ; [M]) |
- ([M] ; fencerel(Before_atomic) ; [RMW] ; po? ; [M]) |
- ([M] ; po? ; [RMW] ; fencerel(After_atomic) ; [M]) |
- ([M] ; po? ; [LKW] ; fencerel(After_spinlock) ; [M])
+ ([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) |
+ ([M] ; po? ; [RMW] ; fencerel(After-atomic) ; [M]) |
+ ([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M])
let gp = po ; [Sync-rcu] ; po?

let strong-fence = mb | gp
diff --git a/tools/memory-model/linux-kernel.def b/tools/memory-model/linux-kernel.def
index a397387f77cc..f5a1eb04cb64 100644
--- a/tools/memory-model/linux-kernel.def
+++ b/tools/memory-model/linux-kernel.def
@@ -21,9 +21,9 @@ smp_mb() { __fence{mb} ; }
smp_rmb() { __fence{rmb} ; }
smp_wmb() { __fence{wmb} ; }
smp_read_barrier_depends() { __fence{rb_dep}; }
-smp_mb__before_atomic() { __fence{before_atomic} ; }
-smp_mb__after_atomic() { __fence{after_atomic} ; }
-smp_mb__after_spinlock() { __fence{after_spinlock} ; }
+smp_mb__before_atomic() { __fence{before-atomic} ; }
+smp_mb__after_atomic() { __fence{after-atomic} ; }
+smp_mb__after_spinlock() { __fence{after-spinlock} ; }

// Exchange
xchg(X,V) __xchg{mb}(X,V)