projects/linux·commit cfebe563

cgroups: fix lockdep subclasses overflow

cfebe563 · Li Zefan <[email protected]> · 2009-02-11 13:04:36 -08:00

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: Li Zefan <[email protected]>
Acked-by: Paul Menage <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Commit
cfebe563bd0a3ff97e1bc167123120d59c7a84db
Parents
01c4a428

Changes

2 files changed · +3 −1

FileStatusAddDelContent
include/linux/cgroup.hmodified+1−0View file
kernel/cgroup.cmodified+2−1View file

include/linux/cgroup.h

View file
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index e4e8e11..499900d 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -378,6 +378,7 @@ struct cgroup_subsys {
* - initiating hotplug events
*/
struct mutex hierarchy_mutex;
+ struct lock_class_key subsys_key;
/*
* Link to parent, and list entry in parent's children.

kernel/cgroup.c

View file
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 5a54ff4..e14db9c 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2351,7 +2351,7 @@ static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
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);
+ mutex_lock(&ss->hierarchy_mutex);
}
}
@@ -2637,6 +2637,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
BUG_ON(!list_empty(&init_task.tasks));
mutex_init(&ss->hierarchy_mutex);
+ lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
ss->active = 1;
}