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authorChris Down <chris@chrisdown.name>2020-04-01 21:07:33 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-04-02 09:35:29 -0700
commitb3a7822e5e7513006d74946a69bfbbc8d8472e90 (patch)
tree3eb11a32c0ab0fd8cfcb357a08e54f293a57cee7 /mm/memcontrol.c
parent32d087cdd9a1ff179177513a8b5d34bec2f54e62 (diff)
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 <chris@chrisdown.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Roman Gushchin <guro@fb.com> Cc: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/d1e9fbc0379fe8db475d82c8b6fbe048876e12ae.1584034301.git.chris@chrisdown.name Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c8
1 files changed, 4 insertions, 4 deletions
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)