cgroups: fix lock inconsistency in cgroup_clone()
I fixed a bug in cgroup_clone() in Linus' tree in commit 7b574b7
("cgroups: fix a race between cgroup_clone and umount") without noticing
there was a cleanup patch in -mm tree that should be rebased (now commit
104cbd5, "cgroups: use task_lock() for access tsk->cgroups safe in
cgroup_clone()"), thus resulted in lock inconsistency.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2ae7cb4..0066092 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2993,20 +2993,21 @@
mutex_unlock(&cgroup_mutex);
return 0;
}
- task_lock(tsk);
- cg = tsk->cgroups;
- parent = task_cgroup(tsk, subsys->subsys_id);
/* Pin the hierarchy */
- if (!atomic_inc_not_zero(&parent->root->sb->s_active)) {
+ if (!atomic_inc_not_zero(&root->sb->s_active)) {
/* We race with the final deactivate_super() */
mutex_unlock(&cgroup_mutex);
return 0;
}
/* Keep the cgroup alive */
+ task_lock(tsk);
+ parent = task_cgroup(tsk, subsys->subsys_id);
+ cg = tsk->cgroups;
get_css_set(cg);
task_unlock(tsk);
+
mutex_unlock(&cgroup_mutex);
/* Now do the VFS work to create a cgroup */
@@ -3045,7 +3046,7 @@
mutex_unlock(&inode->i_mutex);
put_css_set(cg);
- deactivate_super(parent->root->sb);
+ deactivate_super(root->sb);
/* The cgroup is still accessible in the VFS, but
* we're not going to try to rmdir() it at this
* point. */
@@ -3071,7 +3072,7 @@
mutex_lock(&cgroup_mutex);
put_css_set(cg);
mutex_unlock(&cgroup_mutex);
- deactivate_super(parent->root->sb);
+ deactivate_super(root->sb);
return ret;
}
