From b3a7822e5e7513006d74946a69bfbbc8d8472e90 Mon Sep 17 00:00:00 2001 From: Chris Down Date: Wed, 1 Apr 2020 21:07:33 -0700 Subject: mm, memcg: prevent mem_cgroup_protected store tearing The read side of this is all protected, but we can still tear if multiple iterations of mem_cgroup_protected are going at the same time. There's some intentional racing in mem_cgroup_protected which is ok, but load/store tearing should be avoided. Signed-off-by: Chris Down Signed-off-by: Andrew Morton Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Roman Gushchin Cc: Tejun Heo Link: http://lkml.kernel.org/r/d1e9fbc0379fe8db475d82c8b6fbe048876e12ae.1584034301.git.chris@chrisdown.name Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'mm/memcontrol.c') diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 1cd944c2a734..a96d9015ff73 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6396,14 +6396,14 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root, parent_usage = page_counter_read(&parent->memory); - memcg->memory.emin = effective_protection(usage, parent_usage, + WRITE_ONCE(memcg->memory.emin, effective_protection(usage, parent_usage, READ_ONCE(memcg->memory.min), READ_ONCE(parent->memory.emin), - atomic_long_read(&parent->memory.children_min_usage)); + atomic_long_read(&parent->memory.children_min_usage))); - memcg->memory.elow = effective_protection(usage, parent_usage, + WRITE_ONCE(memcg->memory.elow, effective_protection(usage, parent_usage, memcg->memory.low, READ_ONCE(parent->memory.elow), - atomic_long_read(&parent->memory.children_low_usage)); + atomic_long_read(&parent->memory.children_low_usage))); out: if (usage <= memcg->memory.emin) -- cgit v1.2.3