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Merge branch 'for-3.15-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 

Pull more cgroup fixes from Tejun Heo:
 "Three more patches to fix cgroup_freezer breakage due to the recent
  cgroup internal locking changes - an operation cgroup_freezer was
  using now requires sleepable context and cgroup_freezer was invoking
  that while holding a spin lock.  cgroup_freezer was using an overly
  elaborate hierarchical locking scheme.

  While it's possible to convert the hierarchical spinlocks directly to
  mutexes, this patch simplifies the overall locking so that it uses a
  global mutex.  This has the added benefit of avoiding iterating
  potentially huge number of tasks under a spinlock.  While the patch is
  on the larger side in the devel cycle, the changes made are mostly
  straight-forward and the locking logic is a lot simpler afterwards"

* 'for-3.15-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: fix rcu_read_lock() leak in update_if_frozen()
  cgroup_freezer: replace freezer->lock with freezer_mutex
  cgroup: introduce task_css_is_root()
wifi-calibration
Linus Torvalds 2014-05-21 18:36:40 +09:00
parent 6ab9028d00 36e9d2ebcc
commit 06eb4cc2e7
3 changed files with 65 additions and 68 deletions
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15
include/linux/cgroup.h
View File

@ -473,6 +473,7 @@ struct cftype {
};
extern struct cgroup_root cgrp_dfl_root;
extern struct css_set init_css_set;
static inline bool cgroup_on_dfl(const struct cgroup *cgrp)
{
@ -700,6 +701,20 @@ static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
return task_css_check(task, subsys_id, false);
}
/**
* task_css_is_root - test whether a task belongs to the root css
* @task: the target task
* @subsys_id: the target subsystem ID
*
* Test whether @task belongs to the root css on the specified subsystem.
* May be invoked in any context.
*/
static inline bool task_css_is_root(struct task_struct *task, int subsys_id)
{
return task_css_check(task, subsys_id, true) ==
init_css_set.subsys[subsys_id];
}
static inline struct cgroup *task_cgroup(struct task_struct *task,
int subsys_id)
{

2
kernel/cgroup.c
View File

@ -348,7 +348,7 @@ struct cgrp_cset_link {
* reference-counted, to improve performance when child cgroups
* haven't been created.
*/
static struct css_set init_css_set = {
struct css_set init_css_set = {
.refcount = ATOMIC_INIT(1),
.cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
.tasks = LIST_HEAD_INIT(init_css_set.tasks),

116
kernel/cgroup_freezer.c
View File

@ -21,6 +21,7 @@
#include <linux/uaccess.h>
#include <linux/freezer.h>
#include <linux/seq_file.h>
#include <linux/mutex.h>
/*
* A cgroup is freezing if any FREEZING flags are set. FREEZING_SELF is
@ -42,9 +43,10 @@ enum freezer_state_flags {
struct freezer {
struct cgroup_subsys_state css;
unsigned int state;
spinlock_t lock;
};
static DEFINE_MUTEX(freezer_mutex);
static inline struct freezer *css_freezer(struct cgroup_subsys_state *css)
{
return css ? container_of(css, struct freezer, css) : NULL;
@ -93,7 +95,6 @@ freezer_css_alloc(struct cgroup_subsys_state *parent_css)
if (!freezer)
return ERR_PTR(-ENOMEM);
spin_lock_init(&freezer->lock);
return &freezer->css;
}
@ -110,14 +111,7 @@ static int freezer_css_online(struct cgroup_subsys_state *css)
struct freezer *freezer = css_freezer(css);
struct freezer *parent = parent_freezer(freezer);
/*
* The following double locking and freezing state inheritance
* guarantee that @cgroup can never escape ancestors' freezing
* states. See css_for_each_descendant_pre() for details.
*/
if (parent)
spin_lock_irq(&parent->lock);
spin_lock_nested(&freezer->lock, SINGLE_DEPTH_NESTING);
mutex_lock(&freezer_mutex);
freezer->state |= CGROUP_FREEZER_ONLINE;
@ -126,10 +120,7 @@ static int freezer_css_online(struct cgroup_subsys_state *css)
atomic_inc(&system_freezing_cnt);
}
spin_unlock(&freezer->lock);
if (parent)
spin_unlock_irq(&parent->lock);
mutex_unlock(&freezer_mutex);
return 0;
}
@ -144,14 +135,14 @@ static void freezer_css_offline(struct cgroup_subsys_state *css)
{
struct freezer *freezer = css_freezer(css);
spin_lock_irq(&freezer->lock);
mutex_lock(&freezer_mutex);
if (freezer->state & CGROUP_FREEZING)
atomic_dec(&system_freezing_cnt);
freezer->state = 0;
spin_unlock_irq(&freezer->lock);
mutex_unlock(&freezer_mutex);
}
static void freezer_css_free(struct cgroup_subsys_state *css)
@ -175,7 +166,7 @@ static void freezer_attach(struct cgroup_subsys_state *new_css,
struct task_struct *task;
bool clear_frozen = false;
spin_lock_irq(&freezer->lock);
mutex_lock(&freezer_mutex);
/*
* Make the new tasks conform to the current state of @new_css.
@ -197,21 +188,13 @@ static void freezer_attach(struct cgroup_subsys_state *new_css,
}
}
spin_unlock_irq(&freezer->lock);
/*
* Propagate FROZEN clearing upwards. We may race with
* update_if_frozen(), but as long as both work bottom-up, either
* update_if_frozen() sees child's FROZEN cleared or we clear the
* parent's FROZEN later. No parent w/ !FROZEN children can be
* left FROZEN.
*/
/* propagate FROZEN clearing upwards */
while (clear_frozen && (freezer = parent_freezer(freezer))) {
spin_lock_irq(&freezer->lock);
freezer->state &= ~CGROUP_FROZEN;
clear_frozen = freezer->state & CGROUP_FREEZING;
spin_unlock_irq(&freezer->lock);
}
mutex_unlock(&freezer_mutex);
}
/**
@ -228,9 +211,6 @@ static void freezer_fork(struct task_struct *task)
{
struct freezer *freezer;
rcu_read_lock();
freezer = task_freezer(task);
/*
* The root cgroup is non-freezable, so we can skip locking the
* freezer. This is safe regardless of race with task migration.
@ -238,24 +218,18 @@ static void freezer_fork(struct task_struct *task)
* to do. If we lost and root is the new cgroup, noop is still the
* right thing to do.
*/
if (!parent_freezer(freezer))
goto out;
if (task_css_is_root(task, freezer_cgrp_id))
return;
/*
* Grab @freezer->lock and freeze @task after verifying @task still
* belongs to @freezer and it's freezing. The former is for the
* case where we have raced against task migration and lost and
* @task is already in a different cgroup which may not be frozen.
* This isn't strictly necessary as freeze_task() is allowed to be
* called spuriously but let's do it anyway for, if nothing else,
* documentation.
*/
spin_lock_irq(&freezer->lock);
if (freezer == task_freezer(task) && (freezer->state & CGROUP_FREEZING))
mutex_lock(&freezer_mutex);
rcu_read_lock();
freezer = task_freezer(task);
if (freezer->state & CGROUP_FREEZING)
freeze_task(task);
spin_unlock_irq(&freezer->lock);
out:
rcu_read_unlock();
mutex_unlock(&freezer_mutex);
}
/**
@ -281,22 +255,24 @@ static void update_if_frozen(struct cgroup_subsys_state *css)
struct css_task_iter it;
struct task_struct *task;
WARN_ON_ONCE(!rcu_read_lock_held());
spin_lock_irq(&freezer->lock);
lockdep_assert_held(&freezer_mutex);
if (!(freezer->state & CGROUP_FREEZING) ||
(freezer->state & CGROUP_FROZEN))
goto out_unlock;
return;
/* are all (live) children frozen? */
rcu_read_lock();
css_for_each_child(pos, css) {
struct freezer *child = css_freezer(pos);
if ((child->state & CGROUP_FREEZER_ONLINE) &&
!(child->state & CGROUP_FROZEN))
goto out_unlock;
!(child->state & CGROUP_FROZEN)) {
rcu_read_unlock();
return;
}
}
rcu_read_unlock();
/* are all tasks frozen? */
css_task_iter_start(css, &it);
@ -317,21 +293,29 @@ static void update_if_frozen(struct cgroup_subsys_state *css)
freezer->state |= CGROUP_FROZEN;
out_iter_end:
css_task_iter_end(&it);
out_unlock:
spin_unlock_irq(&freezer->lock);
}
static int freezer_read(struct seq_file *m, void *v)
{
struct cgroup_subsys_state *css = seq_css(m), *pos;
mutex_lock(&freezer_mutex);
rcu_read_lock();
/* update states bottom-up */
css_for_each_descendant_post(pos, css)
css_for_each_descendant_post(pos, css) {
if (!css_tryget(pos))
continue;
rcu_read_unlock();
update_if_frozen(pos);
rcu_read_lock();
css_put(pos);
}
rcu_read_unlock();
mutex_unlock(&freezer_mutex);
seq_puts(m, freezer_state_strs(css_freezer(css)->state));
seq_putc(m, '\n');
@ -373,7 +357,7 @@ static void freezer_apply_state(struct freezer *freezer, bool freeze,
unsigned int state)
{
/* also synchronizes against task migration, see freezer_attach() */
lockdep_assert_held(&freezer->lock);
lockdep_assert_held(&freezer_mutex);
if (!(freezer->state & CGROUP_FREEZER_ONLINE))
return;
@ -414,31 +398,29 @@ static void freezer_change_state(struct freezer *freezer, bool freeze)
* descendant will try to inherit its parent's FREEZING state as
* CGROUP_FREEZING_PARENT.
*/
mutex_lock(&freezer_mutex);
rcu_read_lock();
css_for_each_descendant_pre(pos, &freezer->css) {
struct freezer *pos_f = css_freezer(pos);
struct freezer *parent = parent_freezer(pos_f);
spin_lock_irq(&pos_f->lock);
if (!css_tryget(pos))
continue;
rcu_read_unlock();
if (pos_f == freezer) {
if (pos_f == freezer)
freezer_apply_state(pos_f, freeze,
CGROUP_FREEZING_SELF);
} else {
/*
* Our update to @parent->state is already visible
* which is all we need. No need to lock @parent.
* For more info on synchronization, see
* freezer_post_create().
*/
else
freezer_apply_state(pos_f,
parent->state & CGROUP_FREEZING,
CGROUP_FREEZING_PARENT);
}
spin_unlock_irq(&pos_f->lock);
rcu_read_lock();
css_put(pos);
}
rcu_read_unlock();
mutex_unlock(&freezer_mutex);
}
static int freezer_write(struct cgroup_subsys_state *css, struct cftype *cft,