diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 893b7b502e18673d16a130debac7bd06facc3a52..89428b9d99334ed9a2ebf8b36430567febbe7459 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -42,6 +42,7 @@
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
+#include <linux/rwsem.h>
#include <linux/string.h>
#include <linux/sort.h>
#include <linux/kmod.h>
@@ -341,11 +342,10 @@ static struct css_set init_css_set;
static struct cgrp_cset_link init_cgrp_cset_link;
/*
- * css_set_lock protects the list of css_set objects, and the chain of
- * tasks off each css_set. Nests outside task->alloc_lock due to
- * css_task_iter_start().
+ * css_set_rwsem protects the list of css_set objects, and the chain of
+ * tasks off each css_set.
*/
-static DEFINE_RWLOCK(css_set_lock);
+static DECLARE_RWSEM(css_set_rwsem);
static int css_set_count;
/*
@@ -380,9 +380,9 @@ static void __put_css_set(struct css_set *cset, int taskexit)
*/
if (atomic_add_unless(&cset->refcount, -1, 1))
return;
- write_lock(&css_set_lock);
+ down_write(&css_set_rwsem);
if (!atomic_dec_and_test(&cset->refcount)) {
- write_unlock(&css_set_lock);
+ up_write(&css_set_rwsem);
return;
}
@@ -396,7 +396,7 @@ static void __put_css_set(struct css_set *cset, int taskexit)
list_del(&link->cset_link);
list_del(&link->cgrp_link);
- /* @cgrp can't go away while we're holding css_set_lock */
+ /* @cgrp can't go away while we're holding css_set_rwsem */
if (list_empty(&cgrp->cset_links) && notify_on_release(cgrp)) {
if (taskexit)
set_bit(CGRP_RELEASABLE, &cgrp->flags);
@@ -406,7 +406,7 @@ static void __put_css_set(struct css_set *cset, int taskexit)
kfree(link);
}
- write_unlock(&css_set_lock);
+ up_write(&css_set_rwsem);
kfree_rcu(cset, rcu_head);
}
@@ -627,11 +627,11 @@ static struct css_set *find_css_set(struct css_set *old_cset,
/* First see if we already have a cgroup group that matches
* the desired set */
- read_lock(&css_set_lock);
+ down_read(&css_set_rwsem);
cset = find_existing_css_set(old_cset, cgrp, template);
if (cset)
get_css_set(cset);
- read_unlock(&css_set_lock);
+ up_read(&css_set_rwsem);
if (cset)
return cset;
@@ -655,7 +655,7 @@ static struct css_set *find_css_set(struct css_set *old_cset,
* find_existing_css_set() */
memcpy(cset->subsys, template, sizeof(cset->subsys));
- write_lock(&css_set_lock);
+ down_write(&css_set_rwsem);
/* Add reference counts and links from the new css_set. */
list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
struct cgroup *c = link->cgrp;
@@ -673,7 +673,7 @@ static struct css_set *find_css_set(struct css_set *old_cset,
key = css_set_hash(cset->subsys);
hash_add(css_set_table, &cset->hlist, key);
- write_unlock(&css_set_lock);
+ up_write(&css_set_rwsem);
return cset;
}
@@ -739,14 +739,14 @@ static void cgroup_destroy_root(struct cgroupfs_root *root)
* Release all the links from cset_links to this hierarchy's
* root cgroup
*/
- write_lock(&css_set_lock);
+ down_write(&css_set_rwsem);
list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
list_del(&link->cset_link);
list_del(&link->cgrp_link);
kfree(link);
}
- write_unlock(&css_set_lock);
+ up_write(&css_set_rwsem);
if (!list_empty(&root->root_list)) {
list_del(&root->root_list);
@@ -764,7 +764,7 @@ static void cgroup_destroy_root(struct cgroupfs_root *root)
/*
* Return the cgroup for "task" from the given hierarchy. Must be
- * called with cgroup_mutex held.
+ * called with cgroup_mutex and css_set_rwsem held.
*/
static struct cgroup *task_cgroup_from_root(struct task_struct *task,
struct cgroupfs_root *root)
@@ -772,8 +772,9 @@ static struct cgroup *task_cgroup_from_root(struct task_struct *task,
struct css_set *cset;
struct cgroup *res = NULL;
- BUG_ON(!mutex_is_locked(&cgroup_mutex));
- read_lock(&css_set_lock);
+ lockdep_assert_held(&cgroup_mutex);
+ lockdep_assert_held(&css_set_rwsem);
+
/*
* No need to lock the task - since we hold cgroup_mutex the
* task can't change groups, so the only thing that can happen
@@ -794,7 +795,7 @@ static struct cgroup *task_cgroup_from_root(struct task_struct *task,
}
}
}
- read_unlock(&css_set_lock);
+
BUG_ON(!res);
return res;
}
@@ -1310,7 +1311,7 @@ static void cgroup_enable_task_cg_lists(void)
{
struct task_struct *p, *g;
- write_lock(&css_set_lock);
+ down_write(&css_set_rwsem);
if (use_task_css_set_links)
goto out_unlock;
@@ -1343,7 +1344,7 @@ static void cgroup_enable_task_cg_lists(void)
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
out_unlock:
- write_unlock(&css_set_lock);
+ up_write(&css_set_rwsem);
}
static void init_cgroup_housekeeping(struct cgroup *cgrp)
@@ -1408,7 +1409,7 @@ static int cgroup_setup_root(struct cgroupfs_root *root, unsigned long ss_mask)
root_cgrp->id = ret;
/*
- * We're accessing css_set_count without locking css_set_lock here,
+ * We're accessing css_set_count without locking css_set_rwsem here,
* but that's OK - it can only be increased by someone holding
* cgroup_lock, and that's us. The worst that can happen is that we
* have some link structures left over
@@ -1451,10 +1452,10 @@ static int cgroup_setup_root(struct cgroupfs_root *root, unsigned long ss_mask)
* Link the top cgroup in this hierarchy into all the css_set
* objects.
*/
- write_lock(&css_set_lock);
+ down_write(&css_set_rwsem);
hash_for_each(css_set_table, i, cset, hlist)
link_css_set(&tmp_links, cset, root_cgrp);
- write_unlock(&css_set_lock);
+ up_write(&css_set_rwsem);
BUG_ON(!list_empty(&root_cgrp->children));
BUG_ON(atomic_read(&root->nr_cgrps) != 1);
@@ -1617,6 +1618,7 @@ char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
char *path = NULL;
mutex_lock(&cgroup_mutex);
+ down_read(&css_set_rwsem);
root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
@@ -1629,6 +1631,7 @@ char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
path = buf;
}
+ up_read(&css_set_rwsem);
mutex_unlock(&cgroup_mutex);
return path;
}
@@ -1739,9 +1742,9 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp,
rcu_assign_pointer(tsk->cgroups, new_cset);
task_unlock(tsk);
- write_lock(&css_set_lock);
+ down_write(&css_set_rwsem);
list_move(&tsk->cg_list, &new_cset->tasks);
- write_unlock(&css_set_lock);
+ up_write(&css_set_rwsem);
/*
* We just gained a reference on old_cset by taking it from the
@@ -1799,6 +1802,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
* already PF_EXITING could be freed from underneath us unless we
* take an rcu_read_lock.
*/
+ down_read(&css_set_rwsem);
rcu_read_lock();
do {
struct task_and_cgroup ent;
@@ -1826,6 +1830,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
break;
} while_each_thread(leader, tsk);
rcu_read_unlock();
+ up_read(&css_set_rwsem);
/* remember the number of threads in the array for later. */
group_size = i;
tset.tc_array = group;
@@ -2003,7 +2008,11 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
mutex_lock(&cgroup_mutex);
for_each_active_root(root) {
- struct cgroup *from_cgrp = task_cgroup_from_root(from, root);
+ struct cgroup *from_cgrp;
+
+ down_read(&css_set_rwsem);
+ from_cgrp = task_cgroup_from_root(from, root);
+ up_read(&css_set_rwsem);
retval = cgroup_attach_task(from_cgrp, tsk, false);
if (retval)
@@ -2396,10 +2405,10 @@ static int cgroup_task_count(const struct cgroup *cgrp)
int count = 0;
struct cgrp_cset_link *link;
- read_lock(&css_set_lock);
+ down_read(&css_set_rwsem);
list_for_each_entry(link, &cgrp->cset_links, cset_link)
count += atomic_read(&link->cset->refcount);
- read_unlock(&css_set_lock);
+ up_read(&css_set_rwsem);
return count;
}
@@ -2630,12 +2639,12 @@ static void css_advance_task_iter(struct css_task_iter *it)
*/
void css_task_iter_start(struct cgroup_subsys_state *css,
struct css_task_iter *it)
- __acquires(css_set_lock)
+ __acquires(css_set_rwsem)
{
/* no one should try to iterate before mounting cgroups */
WARN_ON_ONCE(!use_task_css_set_links);
- read_lock(&css_set_lock);
+ down_read(&css_set_rwsem);
it->origin_css = css;
it->cset_link = &css->cgroup->cset_links;
@@ -2683,9 +2692,9 @@ struct task_struct *css_task_iter_next(struct css_task_iter *it)
* Finish task iteration started by css_task_iter_start().
*/
void css_task_iter_end(struct css_task_iter *it)
- __releases(css_set_lock)
+ __releases(css_set_rwsem)
{
- read_unlock(&css_set_lock);
+ up_read(&css_set_rwsem);
}
static inline int started_after_time(struct task_struct *t1,
@@ -2735,7 +2744,7 @@ static inline int started_after(void *p1, void *p2)
*
* @test may be NULL, meaning always true (select all tasks), which
* effectively duplicates css_task_iter_{start,next,end}() but does not
- * lock css_set_lock for the call to @process.
+ * lock css_set_rwsem for the call to @process.
*
* It is guaranteed that @process will act on every task that is a member
* of @css for the duration of this call. This function may or may not
@@ -3867,12 +3876,12 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
lockdep_assert_held(&cgroup_mutex);
/*
- * css_set_lock synchronizes access to ->cset_links and prevents
+ * css_set_rwsem synchronizes access to ->cset_links and prevents
* @cgrp from being removed while __put_css_set() is in progress.
*/
- read_lock(&css_set_lock);
+ down_read(&css_set_rwsem);
empty = list_empty(&cgrp->cset_links);
- read_unlock(&css_set_lock);
+ up_read(&css_set_rwsem);
if (!empty)
return -EBUSY;
@@ -4208,6 +4217,7 @@ int proc_cgroup_show(struct seq_file *m, void *v)
retval = 0;
mutex_lock(&cgroup_mutex);
+ down_read(&css_set_rwsem);
for_each_active_root(root) {
struct cgroup_subsys *ss;
@@ -4233,6 +4243,7 @@ int proc_cgroup_show(struct seq_file *m, void *v)
}
out_unlock:
+ up_read(&css_set_rwsem);
mutex_unlock(&cgroup_mutex);
put_task_struct(tsk);
out_free:
@@ -4328,12 +4339,12 @@ void cgroup_post_fork(struct task_struct *child)
* lock on fork.
*/
if (use_task_css_set_links) {
- write_lock(&css_set_lock);
+ down_write(&css_set_rwsem);
task_lock(child);
if (list_empty(&child->cg_list))
list_add(&child->cg_list, &task_css_set(child)->tasks);
task_unlock(child);
- write_unlock(&css_set_lock);
+ up_write(&css_set_rwsem);
}
/*
@@ -4390,15 +4401,14 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
int i;
/*
- * Unlink from the css_set task list if necessary.
- * Optimistically check cg_list before taking
- * css_set_lock
+ * Unlink from the css_set task list if necessary. Optimistically
+ * check cg_list before taking css_set_rwsem.
*/
if (!list_empty(&tsk->cg_list)) {
- write_lock(&css_set_lock);
+ down_write(&css_set_rwsem);
if (!list_empty(&tsk->cg_list))
list_del_init(&tsk->cg_list);
- write_unlock(&css_set_lock);
+ up_write(&css_set_rwsem);
}
/* Reassign the task to the init_css_set. */
@@ -4650,7 +4660,7 @@ static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
if (!name_buf)
return -ENOMEM;
- read_lock(&css_set_lock);
+ down_read(&css_set_rwsem);
rcu_read_lock();
cset = rcu_dereference(current->cgroups);
list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
@@ -4666,7 +4676,7 @@ static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
c->root->hierarchy_id, name);
}
rcu_read_unlock();
- read_unlock(&css_set_lock);
+ up_read(&css_set_rwsem);
kfree(name_buf);
return 0;
}
@@ -4677,7 +4687,7 @@ static int cgroup_css_links_read(struct seq_file *seq, void *v)
struct cgroup_subsys_state *css = seq_css(seq);
struct cgrp_cset_link *link;
- read_lock(&css_set_lock);
+ down_read(&css_set_rwsem);
list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
struct css_set *cset = link->cset;
struct task_struct *task;
@@ -4693,7 +4703,7 @@ static int cgroup_css_links_read(struct seq_file *seq, void *v)
}
}
}
- read_unlock(&css_set_lock);
+ up_read(&css_set_rwsem);
return 0;
}