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sched_ext: Introduce cgroup_lifetime_notifier 

Other subsystems may make use of the cgroup hierarchy with the cgroup_bpf
support being one such example. For such a feature, it's useful to be able
to hook into cgroup creation and destruction paths to perform
feature-specific initializations and cleanups.

Add cgroup_lifetime_notifier which generates CGROUP_LIFETIME_ONLINE and
CGROUP_LIFETIME_OFFLINE events whenever cgroups are created and destroyed,
respectively.

The next patch will convert cgroup_bpf to use the new notifier and other
uses are planned.

Signed-off-by: Tejun Heo <tj@kernel.org>
pull/1250/head
Tejun Heo 2025-05-14 00:44:44 -04:00
parent cd22cbad1b
commit 9e8c67a9e5
2 changed files with 34 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
include/linux/cgroup.h
View File

@ -19,6 +19,7 @@
#include <linux/kernfs.h>
#include <linux/jump_label.h>
#include <linux/types.h>
#include <linux/notifier.h>
#include <linux/ns_common.h>
#include <linux/nsproxy.h>
#include <linux/user_namespace.h>
@ -40,7 +41,7 @@ struct kernel_clone_args;
#ifdef CONFIG_CGROUPS
enum {
enum css_task_iter_flags {
CSS_TASK_ITER_PROCS = (1U << 0), /* walk only threadgroup leaders */
CSS_TASK_ITER_THREADED = (1U << 1), /* walk all threaded css_sets in the domain */
CSS_TASK_ITER_SKIPPED = (1U << 16), /* internal flags */
@ -66,10 +67,16 @@ struct css_task_iter {
struct list_head iters_node; /* css_set->task_iters */
};
enum cgroup_lifetime_events {
CGROUP_LIFETIME_ONLINE,
CGROUP_LIFETIME_OFFLINE,
};
extern struct file_system_type cgroup_fs_type;
extern struct cgroup_root cgrp_dfl_root;
extern struct css_set init_css_set;
extern spinlock_t css_set_lock;
extern struct blocking_notifier_head cgroup_lifetime_notifier;
#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
#include <linux/cgroup_subsys.h>

27
kernel/cgroup/cgroup.c
View File

@ -95,6 +95,9 @@ EXPORT_SYMBOL_GPL(cgroup_mutex);
EXPORT_SYMBOL_GPL(css_set_lock);
#endif
struct blocking_notifier_head cgroup_lifetime_notifier =
BLOCKING_NOTIFIER_INIT(cgroup_lifetime_notifier);
DEFINE_SPINLOCK(trace_cgroup_path_lock);
char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
static bool cgroup_debug __read_mostly;
@ -1326,6 +1329,7 @@ static void cgroup_destroy_root(struct cgroup_root *root)
{
struct cgroup *cgrp = &root->cgrp;
struct cgrp_cset_link *link, *tmp_link;
int ret;
trace_cgroup_destroy_root(root);
@ -1334,6 +1338,10 @@ static void cgroup_destroy_root(struct cgroup_root *root)
BUG_ON(atomic_read(&root->nr_cgrps));
BUG_ON(!list_empty(&cgrp->self.children));
ret = blocking_notifier_call_chain(&cgroup_lifetime_notifier,
CGROUP_LIFETIME_OFFLINE, cgrp);
WARN_ON_ONCE(notifier_to_errno(ret));
/* Rebind all subsystems back to the default hierarchy */
WARN_ON(rebind_subsystems(&cgrp_dfl_root, root->subsys_mask));
@ -2140,6 +2148,10 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
WARN_ON_ONCE(ret);
}
ret = blocking_notifier_call_chain(&cgroup_lifetime_notifier,
CGROUP_LIFETIME_ONLINE, root_cgrp);
WARN_ON_ONCE(notifier_to_errno(ret));
trace_cgroup_setup_root(root);
/*
@ -5733,6 +5745,15 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
goto out_psi_free;
}
ret = blocking_notifier_call_chain_robust(&cgroup_lifetime_notifier,
CGROUP_LIFETIME_ONLINE,
CGROUP_LIFETIME_OFFLINE, cgrp);
ret = notifier_to_errno(ret);
if (ret) {
cgroup_bpf_offline(cgrp);
goto out_psi_free;
}
/* allocation complete, commit to creation */
spin_lock_irq(&css_set_lock);
for (i = 0; i < level; i++) {
@ -5966,7 +5987,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
struct cgroup *tcgrp, *parent = cgroup_parent(cgrp);
struct cgroup_subsys_state *css;
struct cgrp_cset_link *link;
int ssid;
int ssid, ret;
lockdep_assert_held(&cgroup_mutex);
@ -6027,6 +6048,10 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
if (cgrp->root == &cgrp_dfl_root)
cgroup_bpf_offline(cgrp);
ret = blocking_notifier_call_chain(&cgroup_lifetime_notifier,
CGROUP_LIFETIME_OFFLINE, cgrp);
WARN_ON_ONCE(notifier_to_errno(ret));
/* put the base reference */
percpu_ref_kill(&cgrp->self.refcnt);