On Tue, Dec 15, 2020 at 03:58:06PM +0300, Kirill Tkhai wrote: > 15.12.2020, 15:40, "Johannes Weiner" <hannes@xxxxxxxxxxx>: > > On Mon, Dec 14, 2020 at 02:37:16PM -0800, Yang Shi wrote: > >> The shrink_slab_memcg() races with mem_cgroup_css_online(). A visibility of CSS_ONLINE flag > >> in shrink_slab_memcg()->mem_cgroup_online() does not guarantee that we will see > >> memcg->nodeinfo[nid]->shrinker_maps != NULL. This may occur because of processor reordering > >> on !x86. > >> > >> This seems like the below case: > >> > >> CPU A CPU B > >> store shrinker_map load CSS_ONLINE > >> store CSS_ONLINE load shrinker_map > >> > >> So the memory ordering could be guaranteed by smp_wmb()/smp_rmb() pair. > >> > >> The memory barriers pair will guarantee the ordering between shrinker_deferred and CSS_ONLINE > >> for the following patches as well. > >> > >> Signed-off-by: Yang Shi <shy828301@xxxxxxxxx> > > > > As per previous feedback, please move the misplaced shrinker > > allocation callback from .css_online to .css_alloc. This will get you > > the necessary ordering guarantees from the cgroup core code. > > > Can you read my emails from ktkhai@xxxxxxxxxxxxx? I've already answered > on this question here: https://lkml.org/lkml/2020/12/10/726 > > Check your spam folder, and add my address to allow-list if so. It was indeed in my spam folder. Disregard what I wrote above.
