*/
#include <linux/module.h>
+#include <linux/slab.h>
#include <linux/cgroup.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/seq_file.h>
enum freezer_state {
- STATE_RUNNING = 0,
- STATE_FREEZING,
- STATE_FROZEN,
+ CGROUP_THAWED = 0,
+ CGROUP_FREEZING,
+ CGROUP_FROZEN,
};
struct freezer {
struct freezer, css);
}
-int cgroup_frozen(struct task_struct *task)
+int cgroup_freezing_or_frozen(struct task_struct *task)
{
struct freezer *freezer;
enum freezer_state state;
task_lock(task);
freezer = task_freezer(task);
- state = freezer->state;
+ if (!freezer->css.cgroup->parent)
+ state = CGROUP_THAWED; /* root cgroup can't be frozen */
+ else
+ state = freezer->state;
task_unlock(task);
- return state == STATE_FROZEN;
+ return (state == CGROUP_FREEZING) || (state == CGROUP_FROZEN);
}
/*
* CGROUP_LOCAL_BUFFER_SIZE
*/
static const char *freezer_state_strs[] = {
- "RUNNING",
+ "THAWED",
"FREEZING",
"FROZEN",
};
* Transitions are caused by userspace writes to the freezer.state file.
* The values in parenthesis are state labels. The rest are edge labels.
*
- * (RUNNING) --FROZEN--> (FREEZING) --FROZEN--> (FROZEN)
- * ^ ^ | |
- * | \_______RUNNING_______/ |
- * \_____________________________RUNNING___________/
+ * (THAWED) --FROZEN--> (FREEZING) --FROZEN--> (FROZEN)
+ * ^ ^ | |
+ * | \_______THAWED_______/ |
+ * \__________________________THAWED____________/
*/
struct cgroup_subsys freezer_subsys;
/* 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,
return ERR_PTR(-ENOMEM);
spin_lock_init(&freezer->lock);
- freezer->state = STATE_RUNNING;
+ freezer->state = CGROUP_THAWED;
return &freezer->css;
}
kfree(cgroup_freezer(cgroup));
}
+/* 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) ||
+ (task_is_stopped_or_traced(task) && freezing(task));
+}
+/*
+ * The call to cgroup_lock() in the freezer.state write method prevents
+ * a write to that file racing against an attach, and hence the
+ * can_attach() result will remain valid until the attach completes.
+ */
static int freezer_can_attach(struct cgroup_subsys *ss,
struct cgroup *new_cgroup,
- struct task_struct *task)
+ struct task_struct *task, bool threadgroup)
{
struct freezer *freezer;
- int retval = 0;
/*
- * The call to cgroup_lock() in the freezer.state write method prevents
- * a write to that file racing against an attach, and hence the
- * can_attach() result will remain valid until the attach completes.
+ * 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 == STATE_FROZEN)
- retval = -EBUSY;
- return retval;
+ if (freezer->state == CGROUP_FROZEN)
+ return -EBUSY;
+
+ if (threadgroup) {
+ struct task_struct *c;
+
+ 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;
+ }
+ }
+ rcu_read_unlock();
+ }
+
+ return 0;
}
static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
{
struct freezer *freezer;
- task_lock(task);
+ /*
+ * No lock is needed, since the task isn't on tasklist yet,
+ * so it can't be moved to another cgroup, which means the
+ * freezer won't be removed and will be valid during this
+ * function call. Nevertheless, apply RCU read-side critical
+ * section to suppress RCU lockdep false positives.
+ */
+ rcu_read_lock();
freezer = task_freezer(task);
- task_unlock(task);
+ rcu_read_unlock();
+
+ /*
+ * The root cgroup is non-freezable, so we can skip the
+ * following check.
+ */
+ if (!freezer->css.cgroup->parent)
+ return;
- BUG_ON(freezer->state == STATE_FROZEN);
spin_lock_irq(&freezer->lock);
- /* Locking avoids race with FREEZING -> RUNNING transitions. */
- if (freezer->state == STATE_FREEZING)
+ BUG_ON(freezer->state == CGROUP_FROZEN);
+
+ /* Locking avoids race with FREEZING -> THAWED transitions. */
+ if (freezer->state == CGROUP_FREEZING)
freeze_task(task, true);
spin_unlock_irq(&freezer->lock);
}
/*
* caller must hold freezer->lock
*/
-static void check_if_frozen(struct cgroup *cgroup,
- struct freezer *freezer)
+static void update_freezer_state(struct cgroup *cgroup,
+ struct freezer *freezer)
{
struct cgroup_iter it;
struct task_struct *task;
cgroup_iter_start(cgroup, &it);
while ((task = cgroup_iter_next(cgroup, &it))) {
ntotal++;
- /*
- * Task is frozen or will freeze immediately when next it gets
- * woken
- */
- if (frozen(task) ||
- (task_is_stopped_or_traced(task) && freezing(task)))
+ if (is_task_frozen_enough(task))
nfrozen++;
}
* tasks.
*/
if (nfrozen == ntotal)
- freezer->state = STATE_FROZEN;
+ freezer->state = CGROUP_FROZEN;
+ else if (nfrozen > 0)
+ freezer->state = CGROUP_FREEZING;
+ else
+ freezer->state = CGROUP_THAWED;
cgroup_iter_end(cgroup, &it);
}
freezer = cgroup_freezer(cgroup);
spin_lock_irq(&freezer->lock);
state = freezer->state;
- if (state == STATE_FREEZING) {
+ if (state == CGROUP_FREEZING) {
/* We change from FREEZING to FROZEN lazily if the cgroup was
* only partially frozen when we exitted write. */
- check_if_frozen(cgroup, freezer);
+ update_freezer_state(cgroup, freezer);
state = freezer->state;
}
spin_unlock_irq(&freezer->lock);
struct task_struct *task;
unsigned int num_cant_freeze_now = 0;
- freezer->state = STATE_FREEZING;
+ freezer->state = CGROUP_FREEZING;
cgroup_iter_start(cgroup, &it);
while ((task = cgroup_iter_next(cgroup, &it))) {
if (!freeze_task(task, true))
continue;
- if (task_is_stopped_or_traced(task) && freezing(task))
- /*
- * The freeze flag is set so these tasks will
- * immediately go into the fridge upon waking.
- */
+ if (is_task_frozen_enough(task))
continue;
if (!freezing(task) && !freezer_should_skip(task))
num_cant_freeze_now++;
return num_cant_freeze_now ? -EBUSY : 0;
}
-static int unfreeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
+static void unfreeze_cgroup(struct cgroup *cgroup, struct freezer *freezer)
{
struct cgroup_iter it;
struct task_struct *task;
cgroup_iter_start(cgroup, &it);
while ((task = cgroup_iter_next(cgroup, &it))) {
- int do_wake;
-
- task_lock(task);
- do_wake = __thaw_process(task);
- task_unlock(task);
- if (do_wake)
- wake_up_process(task);
+ thaw_process(task);
}
cgroup_iter_end(cgroup, &it);
- freezer->state = STATE_RUNNING;
- return 0;
+ freezer->state = CGROUP_THAWED;
}
static int freezer_change_state(struct cgroup *cgroup,
int retval = 0;
freezer = cgroup_freezer(cgroup);
+
spin_lock_irq(&freezer->lock);
- check_if_frozen(cgroup, freezer); /* may update freezer->state */
+
+ update_freezer_state(cgroup, freezer);
if (goal_state == freezer->state)
goto out;
- switch (freezer->state) {
- case STATE_RUNNING:
- retval = try_to_freeze_cgroup(cgroup, freezer);
+
+ switch (goal_state) {
+ case CGROUP_THAWED:
+ unfreeze_cgroup(cgroup, freezer);
break;
- case STATE_FREEZING:
- if (goal_state == STATE_FROZEN) {
- /* Userspace is retrying after
- * "/bin/echo FROZEN > freezer.state" returned -EBUSY */
- retval = try_to_freeze_cgroup(cgroup, freezer);
- break;
- }
- /* state == FREEZING and goal_state == RUNNING, so unfreeze */
- case STATE_FROZEN:
- retval = unfreeze_cgroup(cgroup, freezer);
+ case CGROUP_FROZEN:
+ retval = try_to_freeze_cgroup(cgroup, freezer);
break;
default:
- break;
+ BUG();
}
out:
spin_unlock_irq(&freezer->lock);
int retval;
enum freezer_state goal_state;
- if (strcmp(buffer, freezer_state_strs[STATE_RUNNING]) == 0)
- goal_state = STATE_RUNNING;
- else if (strcmp(buffer, freezer_state_strs[STATE_FROZEN]) == 0)
- goal_state = STATE_FROZEN;
+ if (strcmp(buffer, freezer_state_strs[CGROUP_THAWED]) == 0)
+ goal_state = CGROUP_THAWED;
+ else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0)
+ goal_state = CGROUP_FROZEN;
else
- return -EIO;
+ return -EINVAL;
if (!cgroup_lock_live_group(cgroup))
return -ENODEV;
static int freezer_populate(struct cgroup_subsys *ss, struct cgroup *cgroup)
{
+ if (!cgroup->parent)
+ return 0;
return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files));
}
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff