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 <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
---
tools/memory-model/README | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/tools/memory-model/README b/tools/memory-model/README
index fc07b52f2028..409211b1c544 100644
--- a/tools/memory-model/README
+++ b/tools/memory-model/README
@@ -207,11 +207,15 @@ The Linux-kernel memory model (LKMM) has the following limitations:
case as a store release.
b. The "unless" RMW operations are not currently modeled:
- atomic_long_add_unless(), atomic_add_unless(),
- atomic_inc_unless_negative(), and
- atomic_dec_unless_positive(). These can be emulated
+ atomic_long_add_unless(), atomic_inc_unless_negative(),
+ and atomic_dec_unless_positive(). These can be emulated
in litmus tests, for example, by using atomic_cmpxchg().
+ One exception of this limitation is atomic_add_unless(),
+ which is provided directly by herd7 (so no corresponding
+ definition in linux-kernel.def). atomic_add_unless() is
+ modeled by herd7 therefore it can be used in litmus tests.
+
c. The call_rcu() function is not modeled. It can be
emulated in litmus tests by adding another process that
invokes synchronize_rcu() and the body of the callback
--
2.25.0
On Thu, 27 Feb 2020, Boqun Feng wrote:
> 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().
Is this really true? Why does herd treat atomic_add_unless() different
from all the other atomic RMS ops? All the other ones we support do
have entries in linux-kernel.def.
Alan
PS: It seems strange to support atomic_add_unless but not
atomic_long_add_unless. The difference between the two is trivial.
>
> Cc: Luc Maranget <[email protected]>
> Signed-off-by: Boqun Feng <[email protected]>
> ---
> tools/memory-model/README | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/tools/memory-model/README b/tools/memory-model/README
> index fc07b52f2028..409211b1c544 100644
> --- a/tools/memory-model/README
> +++ b/tools/memory-model/README
> @@ -207,11 +207,15 @@ The Linux-kernel memory model (LKMM) has the following limitations:
> case as a store release.
>
> b. The "unless" RMW operations are not currently modeled:
> - atomic_long_add_unless(), atomic_add_unless(),
> - atomic_inc_unless_negative(), and
> - atomic_dec_unless_positive(). These can be emulated
> + atomic_long_add_unless(), atomic_inc_unless_negative(),
> + and atomic_dec_unless_positive(). These can be emulated
> in litmus tests, for example, by using atomic_cmpxchg().
>
> + One exception of this limitation is atomic_add_unless(),
> + which is provided directly by herd7 (so no corresponding
> + definition in linux-kernel.def). atomic_add_unless() is
> + modeled by herd7 therefore it can be used in litmus tests.
> +
> c. The call_rcu() function is not modeled. It can be
> emulated in litmus tests by adding another process that
> invokes synchronize_rcu() and the body of the callback
>
> On Thu, 27 Feb 2020, Boqun Feng wrote:
>
> > 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().
>
> Is this really true? Why does herd treat atomic_add_unless() different
> from all the other atomic RMS ops? All the other ones we support do
> have entries in linux-kernel.def.
I think this to be true :)
As far as I remember atomic_add_unless is quite different fron other atomic
RMW ops and called for a specific all-OCaml implementation, without an
entry in linux-kernel.def. As to atomic_long_add_unless, I was not aware
of its existence.
--Luc
>
> Alan
>
> PS: It seems strange to support atomic_add_unless but not
> atomic_long_add_unless. The difference between the two is trivial.
>
> >
> > Cc: Luc Maranget <[email protected]>
> > Signed-off-by: Boqun Feng <[email protected]>
> > ---
> > tools/memory-model/README | 10 +++++++---
> > 1 file changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/memory-model/README b/tools/memory-model/README
> > index fc07b52f2028..409211b1c544 100644
> > --- a/tools/memory-model/README
> > +++ b/tools/memory-model/README
> > @@ -207,11 +207,15 @@ The Linux-kernel memory model (LKMM) has the following limitations:
> > case as a store release.
> >
> > b. The "unless" RMW operations are not currently modeled:
> > - atomic_long_add_unless(), atomic_add_unless(),
> > - atomic_inc_unless_negative(), and
> > - atomic_dec_unless_positive(). These can be emulated
> > + atomic_long_add_unless(), atomic_inc_unless_negative(),
> > + and atomic_dec_unless_positive(). These can be emulated
> > in litmus tests, for example, by using atomic_cmpxchg().
> >
> > + One exception of this limitation is atomic_add_unless(),
> > + which is provided directly by herd7 (so no corresponding
> > + definition in linux-kernel.def). atomic_add_unless() is
> > + modeled by herd7 therefore it can be used in litmus tests.
> > +
> > c. The call_rcu() function is not modeled. It can be
> > emulated in litmus tests by adding another process that
> > invokes synchronize_rcu() and the body of the callback
> >
On Thu, Feb 27, 2020 at 08:40:45AM +0800, Boqun Feng wrote:
> 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 <[email protected]>
> Signed-off-by: Boqun Feng <[email protected]>
> ---
> tools/memory-model/README | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/tools/memory-model/README b/tools/memory-model/README
> index fc07b52f2028..409211b1c544 100644
> --- a/tools/memory-model/README
> +++ b/tools/memory-model/README
> @@ -207,11 +207,15 @@ The Linux-kernel memory model (LKMM) has the following limitations:
> case as a store release.
>
> b. The "unless" RMW operations are not currently modeled:
> - atomic_long_add_unless(), atomic_add_unless(),
> - atomic_inc_unless_negative(), and
> - atomic_dec_unless_positive(). These can be emulated
> + atomic_long_add_unless(), atomic_inc_unless_negative(),
> + and atomic_dec_unless_positive(). These can be emulated
> in litmus tests, for example, by using atomic_cmpxchg().
>
> + One exception of this limitation is atomic_add_unless(),
> + which is provided directly by herd7 (so no corresponding
> + definition in linux-kernel.def). atomic_add_unless() is
Nit: Two spaces after period?
Andrea
> + modeled by herd7 therefore it can be used in litmus tests.
> +
> c. The call_rcu() function is not modeled. It can be
> emulated in litmus tests by adding another process that
> invokes synchronize_rcu() and the body of the callback
> --
> 2.25.0
>
On Thu, 27 Feb 2020, Luc Maranget wrote:
> > On Thu, 27 Feb 2020, Boqun Feng wrote:
> >
> > > 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().
> >
> > Is this really true? Why does herd treat atomic_add_unless() different
> > from all the other atomic RMS ops? All the other ones we support do
> > have entries in linux-kernel.def.
>
> I think this to be true :)
>
> As far as I remember atomic_add_unless is quite different fron other atomic
> RMW ops and called for a specific all-OCaml implementation, without an
> entry in linux-kernel.def. As to atomic_long_add_unless, I was not aware
> of its existence.
Can you explain what is so different about atomic_add_unless?
Alan