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 <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 >
