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| author | Waiman Long <longman@redhat.com> | 2023-12-07 08:46:14 -0500 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2023-12-07 12:54:59 -1000 |
| commit | a7fb0423c201ba12815877a0b5a68a6a1710b23a (patch) | |
| tree | 00c82ba90d21af7cf6efc50858d83d7756f91ca9 | |
| parent | 3232e7aad11e541da86bbb1fa5ea5737b30bd006 (diff) | |
| download | cgroup-for-6.8.tar.gz | |
cgroup: Move rcu_head up near the top of cgroup_rootcgroup-for-6.8for-6.8
Commit d23b5c577715 ("cgroup: Make operations on the cgroup root_list RCU
safe") adds a new rcu_head to the cgroup_root structure and kvfree_rcu()
for freeing the cgroup_root.
The current implementation of kvfree_rcu(), however, has the limitation
that the offset of the rcu_head structure within the larger data
structure must be less than 4096 or the compilation will fail. See the
macro definition of __is_kvfree_rcu_offset() in include/linux/rcupdate.h
for more information.
By putting rcu_head below the large cgroup structure, any change to the
cgroup structure that makes it larger run the risk of causing build
failure under certain configurations. Commit 77070eeb8821 ("cgroup:
Avoid false cacheline sharing of read mostly rstat_cpu") happens to be
the last straw that breaks it. Fix this problem by moving the rcu_head
structure up before the cgroup structure.
Fixes: d23b5c577715 ("cgroup: Make operations on the cgroup root_list RCU safe")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/lkml/20231207143806.114e0a74@canb.auug.org.au/
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
| -rw-r--r-- | include/linux/cgroup-defs.h | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 5a97ea95b5649e..ea48c861cd3695 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -562,6 +562,10 @@ struct cgroup_root { /* Unique id for this hierarchy. */ int hierarchy_id; + /* A list running through the active hierarchies */ + struct list_head root_list; + struct rcu_head rcu; /* Must be near the top */ + /* * The root cgroup. The containing cgroup_root will be destroyed on its * release. cgrp->ancestors[0] will be used overflowing into the @@ -575,10 +579,6 @@ struct cgroup_root { /* Number of cgroups in the hierarchy, used only for /proc/cgroups */ atomic_t nr_cgrps; - /* A list running through the active hierarchies */ - struct list_head root_list; - struct rcu_head rcu; - /* Hierarchy-specific flags */ unsigned int flags; |