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Revert "cgroup: Make operations on the cgroup root_list RCU safe"

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This reverts commit 45a81667e0 which is
commit d23b5c577715892c87533b13923306acc6243f93 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Ib735fb56a5adb6b0198eebc51b0f9737eaff944b
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
This commit is contained in:
Greg Kroah-Hartman 2024-11-10 08:09:20 +00:00
parent 77867ef6d4
commit 246d613c20
3 changed files with 8 additions and 10 deletions
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1
include/linux/cgroup-defs.h
View File

@ -519,7 +519,6 @@ struct cgroup_root {
/* A list running through the active hierarchies */
struct list_head root_list;
struct rcu_head rcu;
/* Hierarchy-specific flags */
unsigned int flags;

3
kernel/cgroup/cgroup-internal.h
View File

@ -172,8 +172,7 @@ extern struct list_head cgroup_roots;
/* iterate across the hierarchies */
#define for_each_root(root) \
list_for_each_entry_rcu((root), &cgroup_roots, root_list, \
lockdep_is_held(&cgroup_mutex))
list_for_each_entry((root), &cgroup_roots, root_list)
/**
* for_each_subsys - iterate all enabled cgroup subsystems

14
kernel/cgroup/cgroup.c
View File

@ -1328,7 +1328,7 @@ static void cgroup_exit_root_id(struct cgroup_root *root)
void cgroup_free_root(struct cgroup_root *root)
{
kfree_rcu(root, rcu);
kfree(root);
}
static void cgroup_destroy_root(struct cgroup_root *root)
@ -1361,7 +1361,7 @@ static void cgroup_destroy_root(struct cgroup_root *root)
spin_unlock_irq(&css_set_lock);
if (!list_empty(&root->root_list)) {
list_del_rcu(&root->root_list);
list_del(&root->root_list);
cgroup_root_count--;
}
@ -1406,6 +1406,7 @@ current_cgns_cgroup_from_root(struct cgroup_root *root)
}
rcu_read_unlock();
BUG_ON(!res);
return res;
}
@ -1415,6 +1416,7 @@ static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
{
struct cgroup *res = NULL;
lockdep_assert_held(&cgroup_mutex);
lockdep_assert_held(&css_set_lock);
if (cset == &init_css_set) {
@ -1440,9 +1442,7 @@ static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
/*
* Return the cgroup for "task" from the given hierarchy. Must be
* called with css_set_lock held to prevent task's groups from being modified.
* Must be called with either cgroup_mutex or rcu read lock to prevent the
* cgroup root from being destroyed.
* called with cgroup_mutex and css_set_lock held.
*/
struct cgroup *task_cgroup_from_root(struct task_struct *task,
struct cgroup_root *root)
@ -1974,7 +1974,7 @@ void init_cgroup_root(struct cgroup_fs_context *ctx)
struct cgroup_root *root = ctx->root;
struct cgroup *cgrp = &root->cgrp;
INIT_LIST_HEAD_RCU(&root->root_list);
INIT_LIST_HEAD(&root->root_list);
atomic_set(&root->nr_cgrps, 1);
cgrp->root = root;
init_cgroup_housekeeping(cgrp);
@ -2052,7 +2052,7 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
* care of subsystems' refcounts, which are explicitly dropped in
* the failure exit path.
*/
list_add_rcu(&root->root_list, &cgroup_roots);
list_add(&root->root_list, &cgroup_roots);
cgroup_root_count++;
/*