struct freezer, css);
}
-int cgroup_freezing_or_frozen(struct task_struct *task)
+static inline int __cgroup_freezing_or_frozen(struct task_struct *task)
{
- struct freezer *freezer;
- enum freezer_state state;
+ enum freezer_state state = task_freezer(task)->state;
+ return (state == CGROUP_FREEZING) || (state == CGROUP_FROZEN);
+}
+int cgroup_freezing_or_frozen(struct task_struct *task)
+{
+ int result;
task_lock(task);
- freezer = task_freezer(task);
- if (!freezer->css.cgroup->parent)
- state = CGROUP_THAWED; /* root cgroup can't be frozen */
- else
- state = freezer->state;
+ result = __cgroup_freezing_or_frozen(task);
task_unlock(task);
-
- return (state == CGROUP_FREEZING) || (state == CGROUP_FROZEN);
+ return result;
}
/*
/* Locks taken and their ordering
* ------------------------------
- * css_set_lock
* cgroup_mutex (AKA cgroup_lock)
- * task->alloc_lock (AKA task_lock)
* freezer->lock
+ * css_set_lock
+ * task->alloc_lock (AKA task_lock)
* task->sighand->siglock
*
* cgroup code forces css_set_lock to be taken before task->alloc_lock
* freezer_create(), freezer_destroy():
* cgroup_mutex [ by cgroup core ]
*
- * can_attach():
- * cgroup_mutex
+ * freezer_can_attach():
+ * cgroup_mutex (held by caller of can_attach)
*
- * cgroup_frozen():
+ * cgroup_freezing_or_frozen():
* task->alloc_lock (to get task's cgroup)
*
* freezer_fork() (preserving fork() performance means can't take cgroup_mutex):
- * task->alloc_lock (to get task's cgroup)
* freezer->lock
* sighand->siglock (if the cgroup is freezing)
*
* freezer_read():
* cgroup_mutex
* freezer->lock
+ * write_lock css_set_lock (cgroup iterator start)
+ * task->alloc_lock
* read_lock css_set_lock (cgroup iterator start)
*
* freezer_write() (freeze):
* cgroup_mutex
* freezer->lock
+ * write_lock css_set_lock (cgroup iterator start)
+ * task->alloc_lock
* read_lock css_set_lock (cgroup iterator start)
- * sighand->siglock
+ * sighand->siglock (fake signal delivery inside freeze_task())
*
* freezer_write() (unfreeze):
* cgroup_mutex
* freezer->lock
+ * write_lock css_set_lock (cgroup iterator start)
+ * task->alloc_lock
* read_lock css_set_lock (cgroup iterator start)
- * task->alloc_lock (to prevent races with freeze_task())
+ * task->alloc_lock (inside thaw_process(), prevents race with refrigerator())
* sighand->siglock
*/
static struct cgroup_subsys_state *freezer_create(struct cgroup_subsys *ss,
kfree(cgroup_freezer(cgroup));
}
-/* Task is frozen or will freeze immediately when next it gets woken */
+/* task is frozen or will freeze immediately when next it gets woken */
static bool is_task_frozen_enough(struct task_struct *task)
{
return frozen(task) ||
*/
static int freezer_can_attach(struct cgroup_subsys *ss,
struct cgroup *new_cgroup,
- struct task_struct *task, bool threadgroup)
+ struct task_struct *task)
{
struct freezer *freezer;
/*
* Anything frozen can't move or be moved to/from.
- *
- * Since orig_freezer->state == FROZEN means that @task has been
- * frozen, so it's sufficient to check the latter condition.
*/
- if (is_task_frozen_enough(task))
- return -EBUSY;
-
freezer = cgroup_freezer(new_cgroup);
- if (freezer->state == CGROUP_FROZEN)
+ if (freezer->state != CGROUP_THAWED)
return -EBUSY;
- if (threadgroup) {
- struct task_struct *c;
+ return 0;
+}
- rcu_read_lock();
- list_for_each_entry_rcu(c, &task->thread_group, thread_group) {
- if (is_task_frozen_enough(c)) {
- rcu_read_unlock();
- return -EBUSY;
- }
- }
+static int freezer_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
+{
+ rcu_read_lock();
+ if (__cgroup_freezing_or_frozen(tsk)) {
rcu_read_unlock();
+ return -EBUSY;
}
-
+ rcu_read_unlock();
return 0;
}
/*
* caller must hold freezer->lock
*/
-static void update_freezer_state(struct cgroup *cgroup,
+static void update_if_frozen(struct cgroup *cgroup,
struct freezer *freezer)
{
struct cgroup_iter it;
struct task_struct *task;
unsigned int nfrozen = 0, ntotal = 0;
+ enum freezer_state old_state = freezer->state;
cgroup_iter_start(cgroup, &it);
while ((task = cgroup_iter_next(cgroup, &it))) {
nfrozen++;
}
- /*
- * Transition to FROZEN when no new tasks can be added ensures
- * that we never exist in the FROZEN state while there are unfrozen
- * tasks.
- */
- if (nfrozen == ntotal)
- freezer->state = CGROUP_FROZEN;
- else if (nfrozen > 0)
- freezer->state = CGROUP_FREEZING;
- else
- freezer->state = CGROUP_THAWED;
+ if (old_state == CGROUP_THAWED) {
+ BUG_ON(nfrozen > 0);
+ } else if (old_state == CGROUP_FREEZING) {
+ if (nfrozen == ntotal)
+ freezer->state = CGROUP_FROZEN;
+ } else { /* old_state == CGROUP_FROZEN */
+ BUG_ON(nfrozen != ntotal);
+ }
+
cgroup_iter_end(cgroup, &it);
}
if (state == CGROUP_FREEZING) {
/* We change from FREEZING to FROZEN lazily if the cgroup was
* only partially frozen when we exitted write. */
- update_freezer_state(cgroup, freezer);
+ update_if_frozen(cgroup, freezer);
state = freezer->state;
}
spin_unlock_irq(&freezer->lock);
spin_lock_irq(&freezer->lock);
- update_freezer_state(cgroup, freezer);
+ update_if_frozen(cgroup, freezer);
if (goal_state == freezer->state)
goto out;
.populate = freezer_populate,
.subsys_id = freezer_subsys_id,
.can_attach = freezer_can_attach,
+ .can_attach_task = freezer_can_attach_task,
+ .pre_attach = NULL,
+ .attach_task = NULL,
.attach = NULL,
.fork = freezer_fork,
.exit = NULL,
Code Review / linux-2.6.git / blobdiff