Hello, Li.

On Thu, Jun 28, 2012 at 02:07:51PM +0800, Li Zefan wrote:

quoted

Hmm... fa980ca87d "cgroup: superblock can't be released with active
dentries" is supposed to have fixed that.  Looking into it.

I think I know what happened here:

umount
  deativate_super(sb)
                       dput(subdir)
                         subdir->d_count--
                         d_release(subdir)
                           deactivate_super(sb)
                             shrink_dcache_for_umount(sb)
                               BUG(root->d_count)!!
                         root->d_count--

Can you please elaborate a bit?  I'm not really following?  Where does
the last root->d_count-- come from?

I use this script to reproduce the bug:

mount -t cgroup -o cpu xxx /mnt
mkdir /mnt/sub
sleep 100 < /mnt/sub &
kill $!
wait $!
rmdir /mnt/sub
umount /mnt

Unfortunately, this doesn't reproduce the bug here either. :(

Thanks.

-- 
tejun