Commit cfebe563 authored by Li Zefan's avatar Li Zefan Committed by Linus Torvalds

cgroups: fix lockdep subclasses overflow

I enabled all cgroup subsystems when compiling kernel, and then:
 # mount -t cgroup -o net_cls xxx /mnt
 # mkdir /mnt/0

This showed up immediately:
 BUG: MAX_LOCKDEP_SUBCLASSES too low!
 turning off the locking correctness validator.

It's caused by the cgroup hierarchy lock:
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		if (ss->root == root)
			mutex_lock_nested(&ss->hierarchy_mutex, i);
	}

Now we have 9 cgroup subsystems, and the above 'i' for net_cls is 8, but
MAX_LOCKDEP_SUBCLASSES is 8.

This patch uses different lockdep keys for different subsystems.
Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Acked-by: default avatarPaul Menage <menage@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 01c4a428
...@@ -378,6 +378,7 @@ struct cgroup_subsys { ...@@ -378,6 +378,7 @@ struct cgroup_subsys {
* - initiating hotplug events * - initiating hotplug events
*/ */
struct mutex hierarchy_mutex; struct mutex hierarchy_mutex;
struct lock_class_key subsys_key;
/* /*
* Link to parent, and list entry in parent's children. * Link to parent, and list entry in parent's children.
......
...@@ -2351,7 +2351,7 @@ static void cgroup_lock_hierarchy(struct cgroupfs_root *root) ...@@ -2351,7 +2351,7 @@ static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i]; struct cgroup_subsys *ss = subsys[i];
if (ss->root == root) if (ss->root == root)
mutex_lock_nested(&ss->hierarchy_mutex, i); mutex_lock(&ss->hierarchy_mutex);
} }
} }
...@@ -2637,6 +2637,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss) ...@@ -2637,6 +2637,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
BUG_ON(!list_empty(&init_task.tasks)); BUG_ON(!list_empty(&init_task.tasks));
mutex_init(&ss->hierarchy_mutex); mutex_init(&ss->hierarchy_mutex);
lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
ss->active = 1; ss->active = 1;
} }
......
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