CGRP_WAIT_ON_RMDIR,
};
+/* which pidlist file are we talking about? */
+enum cgroup_filetype {
+ CGROUP_FILE_PROCS,
+ CGROUP_FILE_TASKS,
+};
+
+/*
+ * A pidlist is a list of pids that virtually represents the contents of one
+ * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
+ * a pair (one each for procs, tasks) for each pid namespace that's relevant
+ * to the cgroup.
+ */
struct cgroup_pidlist {
- /* protects the other fields */
- struct rw_semaphore mutex;
+ /*
+ * used to find which pidlist is wanted. doesn't change as long as
+ * this particular list stays in the list.
+ */
+ struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
/* array of xids */
pid_t *list;
/* how many elements the above list has */
int length;
/* how many files are using the current array */
int use_count;
+ /* each of these stored in a list by its cgroup */
+ struct list_head links;
+ /* pointer to the cgroup we belong to, for list removal purposes */
+ struct cgroup *owner;
+ /* protects the other fields */
+ struct rw_semaphore mutex;
};
struct cgroup {
*/
struct list_head release_list;
- /* we will have two separate pidlists, one for pids (the tasks file)
- * and one for tgids (the procs file). */
- struct cgroup_pidlist tasks, procs;
+ /*
+ * list of pidlists, up to two for each namespace (one for procs, one
+ * for tasks); created on demand.
+ */
+ struct list_head pidlists;
+ struct mutex pidlist_mutex;
/* For RCU-protected deletion */
struct rcu_head rcu_head;
*/
deactivate_super(cgrp->root->sb);
+ /*
+ * if we're getting rid of the cgroup, refcount should ensure
+ * that there are no pidlists left.
+ */
+ BUG_ON(!list_empty(&cgrp->pidlists));
+
call_rcu(&cgrp->rcu_head, free_cgroup_rcu);
}
iput(inode);
INIT_LIST_HEAD(&cgrp->children);
INIT_LIST_HEAD(&cgrp->css_sets);
INIT_LIST_HEAD(&cgrp->release_list);
- init_rwsem(&(cgrp->tasks.mutex));
- init_rwsem(&(cgrp->procs.mutex));
+ INIT_LIST_HEAD(&cgrp->pidlists);
+ mutex_init(&cgrp->pidlist_mutex);
}
static void init_cgroup_root(struct cgroupfs_root *root)
return *(pid_t *)a - *(pid_t *)b;
}
+/*
+ * find the appropriate pidlist for our purpose (given procs vs tasks)
+ * returns with the lock on that pidlist already held, and takes care
+ * of the use count, or returns NULL with no locks held if we're out of
+ * memory.
+ */
+static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
+ enum cgroup_filetype type)
+{
+ struct cgroup_pidlist *l;
+ /* don't need task_nsproxy() if we're looking at ourself */
+ struct pid_namespace *ns = get_pid_ns(current->nsproxy->pid_ns);
+ /*
+ * We can't drop the pidlist_mutex before taking the l->mutex in case
+ * the last ref-holder is trying to remove l from the list at the same
+ * time. Holding the pidlist_mutex precludes somebody taking whichever
+ * list we find out from under us - compare release_pid_array().
+ */
+ mutex_lock(&cgrp->pidlist_mutex);
+ list_for_each_entry(l, &cgrp->pidlists, links) {
+ if (l->key.type == type && l->key.ns == ns) {
+ /* found a matching list - drop the extra refcount */
+ put_pid_ns(ns);
+ /* make sure l doesn't vanish out from under us */
+ down_write(&l->mutex);
+ mutex_unlock(&cgrp->pidlist_mutex);
+ l->use_count++;
+ return l;
+ }
+ }
+ /* entry not found; create a new one */
+ l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
+ if (!l) {
+ mutex_unlock(&cgrp->pidlist_mutex);
+ put_pid_ns(ns);
+ return l;
+ }
+ init_rwsem(&l->mutex);
+ down_write(&l->mutex);
+ l->key.type = type;
+ l->key.ns = ns;
+ l->use_count = 0; /* don't increment here */
+ l->list = NULL;
+ l->owner = cgrp;
+ list_add(&l->links, &cgrp->pidlists);
+ mutex_unlock(&cgrp->pidlist_mutex);
+ return l;
+}
+
/*
* Load a cgroup's pidarray with either procs' tgids or tasks' pids
*/
-static int pidlist_array_load(struct cgroup *cgrp, bool procs)
+static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
+ struct cgroup_pidlist **lp)
{
pid_t *array;
int length;
if (unlikely(n == length))
break;
/* get tgid or pid for procs or tasks file respectively */
- pid = (procs ? task_tgid_vnr(tsk) : task_pid_vnr(tsk));
+ if (type == CGROUP_FILE_PROCS)
+ pid = task_tgid_vnr(tsk);
+ else
+ pid = task_pid_vnr(tsk);
if (pid > 0) /* make sure to only use valid results */
array[n++] = pid;
}
length = n;
/* now sort & (if procs) strip out duplicates */
sort(array, length, sizeof(pid_t), cmppid, NULL);
- if (procs) {
+ if (type == CGROUP_FILE_PROCS)
length = pidlist_uniq(&array, length);
- l = &(cgrp->procs);
- } else {
- l = &(cgrp->tasks);
+ l = cgroup_pidlist_find(cgrp, type);
+ if (!l) {
+ kfree(array);
+ return -ENOMEM;
}
- /* store array in cgroup, freeing old if necessary */
- down_write(&l->mutex);
+ /* store array, freeing old if necessary - lock already held */
kfree(l->list);
l->list = array;
l->length = length;
l->use_count++;
up_write(&l->mutex);
+ *lp = l;
return 0;
}
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
{
+ /*
+ * the case where we're the last user of this particular pidlist will
+ * have us remove it from the cgroup's list, which entails taking the
+ * mutex. since in pidlist_find the pidlist->lock depends on cgroup->
+ * pidlist_mutex, we have to take pidlist_mutex first.
+ */
+ mutex_lock(&l->owner->pidlist_mutex);
down_write(&l->mutex);
BUG_ON(!l->use_count);
if (!--l->use_count) {
+ /* we're the last user if refcount is 0; remove and free */
+ list_del(&l->links);
+ mutex_unlock(&l->owner->pidlist_mutex);
kfree(l->list);
- l->list = NULL;
- l->length = 0;
+ put_pid_ns(l->key.ns);
+ up_write(&l->mutex);
+ kfree(l);
+ return;
}
+ mutex_unlock(&l->owner->pidlist_mutex);
up_write(&l->mutex);
}
* in the cgroup.
*/
/* helper function for the two below it */
-static int cgroup_pidlist_open(struct file *file, bool procs)
+static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
{
struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
- struct cgroup_pidlist *l = (procs ? &cgrp->procs : &cgrp->tasks);
+ struct cgroup_pidlist *l;
int retval;
/* Nothing to do for write-only files */
return 0;
/* have the array populated */
- retval = pidlist_array_load(cgrp, procs);
+ retval = pidlist_array_load(cgrp, type, &l);
if (retval)
return retval;
/* configure file information */
}
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
- return cgroup_pidlist_open(file, false);
+ return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
- return cgroup_pidlist_open(file, true);
+ return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
}
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
projects / GitHub / LineageOS / android_kernel_motorola_exynos9610.git / commitdiff