On Fri, 19 May 2023 14:52:50 -0400 Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > On Thu, May 18, 2023 at 6:40 PM SeongJae Park <sj@xxxxxxxxxx> wrote: > > > > The document says we can avoid extra smp_rmb() in lockless_lookup() and > > extra _release() in insert function when hlist_nulls is used. However, > > the example code snippet for the insert function is still using the > > extra _release(). Drop it. > > > > Signed-off-by: SeongJae Park <sj@xxxxxxxxxx> > > --- > > Documentation/RCU/rculist_nulls.rst | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/Documentation/RCU/rculist_nulls.rst b/Documentation/RCU/rculist_nulls.rst > > index 5cd6f3f8810f..463270273d89 100644 > > --- a/Documentation/RCU/rculist_nulls.rst > > +++ b/Documentation/RCU/rculist_nulls.rst > > @@ -191,7 +191,7 @@ scan the list again without harm. > > obj = kmem_cache_alloc(cachep); > > lock_chain(); // typically a spin_lock() > > obj->key = key; > > - atomic_set_release(&obj->refcnt, 1); // key before refcnt > > + atomic_set(&obj->refcnt, 1); > > /* > > * insert obj in RCU way (readers might be traversing chain) > > */ > > If write to ->refcnt of 1 is reordered with setting of ->key, what > prevents the 'lookup algorithm' from doing a key match (obj->key == > key) before the refcount has been initialized? > > Are we sure the reordering mentioned in the document is the same as > the reordering prevented by the atomic_set_release()? Paul, may I ask your opinion? Thanks, SJ > > For the other 3 patches, feel free to add: > Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> > > thanks, > > - Joel
