> 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 <luc.maranget@xxxxxxxx> > > Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx> > > --- > > 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 > >
