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Merge branch 'for-6.0-fixes' into for-6.1

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Pulling to receive 43626dade3 ("group: Add missing cpus_read_lock() to
cgroup_attach_task_all()") for a follow-up patch.
This commit is contained in:
Tejun Heo 2022-08-26 11:13:39 -10:00
commit 265efc941f
6 changed files with 63 additions and 39 deletions
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5
include/linux/cgroup.h
View File

@ -732,11 +732,6 @@ static inline struct cgroup *cgroup_parent(struct cgroup *cgrp)
return NULL;
}
static inline struct psi_group *cgroup_psi(struct cgroup *cgrp)
{
return NULL;
}
static inline bool cgroup_psi_enabled(void)
{
return false;

2
include/linux/psi.h
View File

@ -27,7 +27,7 @@ void psi_memstall_leave(unsigned long *flags);
int psi_show(struct seq_file *s, struct psi_group *group, enum psi_res res);
struct psi_trigger *psi_trigger_create(struct psi_group *group,
char *buf, size_t nbytes, enum psi_res res);
char *buf, enum psi_res res);
void psi_trigger_destroy(struct psi_trigger *t);
__poll_t psi_trigger_poll(void **trigger_ptr, struct file *file,

2
kernel/cgroup/cgroup-v1.c
View File

@ -59,6 +59,7 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
int retval = 0;
mutex_lock(&cgroup_mutex);
cpus_read_lock();
percpu_down_write(&cgroup_threadgroup_rwsem);
for_each_root(root) {
struct cgroup *from_cgrp;
@ -72,6 +73,7 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
break;
}
percpu_up_write(&cgroup_threadgroup_rwsem);
cpus_read_unlock();
mutex_unlock(&cgroup_mutex);
return retval;

80
kernel/cgroup/cgroup.c
View File

@ -1820,6 +1820,7 @@ int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
if (ss->css_rstat_flush) {
list_del_rcu(&css->rstat_css_node);
synchronize_rcu();
list_add_rcu(&css->rstat_css_node,
&dcgrp->rstat_css_list);
}
@ -2369,6 +2370,47 @@ int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
}
EXPORT_SYMBOL_GPL(task_cgroup_path);
/**
* cgroup_attach_lock - Lock for ->attach()
* @lock_threadgroup: whether to down_write cgroup_threadgroup_rwsem
*
* cgroup migration sometimes needs to stabilize threadgroups against forks and
* exits by write-locking cgroup_threadgroup_rwsem. However, some ->attach()
* implementations (e.g. cpuset), also need to disable CPU hotplug.
* Unfortunately, letting ->attach() operations acquire cpus_read_lock() can
* lead to deadlocks.
*
* Bringing up a CPU may involve creating and destroying tasks which requires
* read-locking threadgroup_rwsem, so threadgroup_rwsem nests inside
* cpus_read_lock(). If we call an ->attach() which acquires the cpus lock while
* write-locking threadgroup_rwsem, the locking order is reversed and we end up
* waiting for an on-going CPU hotplug operation which in turn is waiting for
* the threadgroup_rwsem to be released to create new tasks. For more details:
*
* http://lkml.kernel.org/r/20220711174629.uehfmqegcwn2lqzu@wubuntu
*
* Resolve the situation by always acquiring cpus_read_lock() before optionally
* write-locking cgroup_threadgroup_rwsem. This allows ->attach() to assume that
* CPU hotplug is disabled on entry.
*/
static void cgroup_attach_lock(bool lock_threadgroup)
{
cpus_read_lock();
if (lock_threadgroup)
percpu_down_write(&cgroup_threadgroup_rwsem);
}
/**
* cgroup_attach_unlock - Undo cgroup_attach_lock()
* @lock_threadgroup: whether to up_write cgroup_threadgroup_rwsem
*/
static void cgroup_attach_unlock(bool lock_threadgroup)
{
if (lock_threadgroup)
percpu_up_write(&cgroup_threadgroup_rwsem);
cpus_read_unlock();
}
/**
* cgroup_migrate_add_task - add a migration target task to a migration context
* @task: target task
@ -2841,8 +2883,7 @@ int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
}
struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup,
bool *locked)
__acquires(&cgroup_threadgroup_rwsem)
bool *threadgroup_locked)
{
struct task_struct *tsk;
pid_t pid;
@ -2859,12 +2900,8 @@ struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup,
* Therefore, we can skip the global lock.
*/
lockdep_assert_held(&cgroup_mutex);
if (pid || threadgroup) {
percpu_down_write(&cgroup_threadgroup_rwsem);
*locked = true;
} else {
*locked = false;
}
*threadgroup_locked = pid || threadgroup;
cgroup_attach_lock(*threadgroup_locked);
rcu_read_lock();
if (pid) {
@ -2895,17 +2932,14 @@ struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup,
goto out_unlock_rcu;
out_unlock_threadgroup:
if (*locked) {
percpu_up_write(&cgroup_threadgroup_rwsem);
*locked = false;
}
cgroup_attach_unlock(*threadgroup_locked);
*threadgroup_locked = false;
out_unlock_rcu:
rcu_read_unlock();
return tsk;
}
void cgroup_procs_write_finish(struct task_struct *task, bool locked)
__releases(&cgroup_threadgroup_rwsem)
void cgroup_procs_write_finish(struct task_struct *task, bool threadgroup_locked)
{
struct cgroup_subsys *ss;
int ssid;
@ -2913,8 +2947,8 @@ void cgroup_procs_write_finish(struct task_struct *task, bool locked)
/* release reference from cgroup_procs_write_start() */
put_task_struct(task);
if (locked)
percpu_up_write(&cgroup_threadgroup_rwsem);
cgroup_attach_unlock(threadgroup_locked);
for_each_subsys(ss, ssid)
if (ss->post_attach)
ss->post_attach();
@ -3000,8 +3034,7 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp)
* write-locking can be skipped safely.
*/
has_tasks = !list_empty(&mgctx.preloaded_src_csets);
if (has_tasks)
percpu_down_write(&cgroup_threadgroup_rwsem);
cgroup_attach_lock(has_tasks);
/* NULL dst indicates self on default hierarchy */
ret = cgroup_migrate_prepare_dst(&mgctx);
@ -3022,8 +3055,7 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp)
ret = cgroup_migrate_execute(&mgctx);
out_finish:
cgroup_migrate_finish(&mgctx);
if (has_tasks)
percpu_up_write(&cgroup_threadgroup_rwsem);
cgroup_attach_unlock(has_tasks);
return ret;
}
@ -3698,7 +3730,7 @@ static ssize_t cgroup_pressure_write(struct kernfs_open_file *of, char *buf,
}
psi = cgroup_ino(cgrp) == 1 ? &psi_system : cgrp->psi;
new = psi_trigger_create(psi, buf, nbytes, res);
new = psi_trigger_create(psi, buf, res);
if (IS_ERR(new)) {
cgroup_put(cgrp);
return PTR_ERR(new);
@ -4971,13 +5003,13 @@ static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
struct task_struct *task;
const struct cred *saved_cred;
ssize_t ret;
bool locked;
bool threadgroup_locked;
dst_cgrp = cgroup_kn_lock_live(of->kn, false);
if (!dst_cgrp)
return -ENODEV;
task = cgroup_procs_write_start(buf, threadgroup, &locked);
task = cgroup_procs_write_start(buf, threadgroup, &threadgroup_locked);
ret = PTR_ERR_OR_ZERO(task);
if (ret)
goto out_unlock;
@ -5003,7 +5035,7 @@ static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
ret = cgroup_attach_task(dst_cgrp, task, threadgroup);
out_finish:
cgroup_procs_write_finish(task, locked);
cgroup_procs_write_finish(task, threadgroup_locked);
out_unlock:
cgroup_kn_unlock(of->kn);

3
kernel/cgroup/cpuset.c
View File

@ -2289,7 +2289,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
cgroup_taskset_first(tset, &css);
cs = css_cs(css);
cpus_read_lock();
lockdep_assert_cpus_held(); /* see cgroup_attach_lock() */
percpu_down_write(&cpuset_rwsem);
guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
@ -2343,7 +2343,6 @@ static void cpuset_attach(struct cgroup_taskset *tset)
wake_up(&cpuset_attach_wq);
percpu_up_write(&cpuset_rwsem);
cpus_read_unlock();
}
/* The various types of files and directories in a cpuset file system */

10
kernel/sched/psi.c
View File

@ -190,12 +190,8 @@ static void group_init(struct psi_group *group)
/* Init trigger-related members */
mutex_init(&group->trigger_lock);
INIT_LIST_HEAD(&group->triggers);
memset(group->nr_triggers, 0, sizeof(group->nr_triggers));
group->poll_states = 0;
group->poll_min_period = U32_MAX;
memset(group->polling_total, 0, sizeof(group->polling_total));
group->polling_next_update = ULLONG_MAX;
group->polling_until = 0;
init_waitqueue_head(&group->poll_wait);
timer_setup(&group->poll_timer, poll_timer_fn, 0);
rcu_assign_pointer(group->poll_task, NULL);
@ -957,7 +953,7 @@ int psi_cgroup_alloc(struct cgroup *cgroup)
if (static_branch_likely(&psi_disabled))
return 0;
cgroup->psi = kmalloc(sizeof(struct psi_group), GFP_KERNEL);
cgroup->psi = kzalloc(sizeof(struct psi_group), GFP_KERNEL);
if (!cgroup->psi)
return -ENOMEM;
@ -1091,7 +1087,7 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res)
}
struct psi_trigger *psi_trigger_create(struct psi_group *group,
char *buf, size_t nbytes, enum psi_res res)
char *buf, enum psi_res res)
{
struct psi_trigger *t;
enum psi_states state;
@ -1320,7 +1316,7 @@ static ssize_t psi_write(struct file *file, const char __user *user_buf,
return -EBUSY;
}
new = psi_trigger_create(&psi_system, buf, nbytes, res);
new = psi_trigger_create(&psi_system, buf, res);
if (IS_ERR(new)) {
mutex_unlock(&seq->lock);
return PTR_ERR(new);