I got a freeze (without lockdep warning) with a small out-of-tree patch
applied on 2.6.38. It seems to me that the deadlock occurred when running
pivot_root(). I guess it is spinning at spin_lock() below.
Is below lock dependency safe?
d_path():
write_seqlock(&rename_lock);
br_read_lock(vfsmount_lock);
spin_lock(&dentry->d_lock);
spin_unlock(&dentry->d_lock);
br_read_unlock(vfsmount_lock);
write_sequnlock(&rename_lock);
pivot_root():
down_write(&namespace_sem);
mutex_lock(&old.dentry->d_inode->i_mutex);
br_write_lock(vfsmount_lock);
spin_lock(&dentry->d_lock);
spin_unlock(&dentry->d_lock);
br_write_unlock(vfsmount_lock);
mutex_unlock(&old.dentry->d_inode->i_mutex);
up_write(&namespace_sem);
[ 384.711037] 8 locks held by make/6110:
[ 384.711037] #0: (&ccs_ss){.+.+.+}, at: [<c11bc320>] ccs_path_perm+0x0/0x1c0
[ 384.711037] #1: (rename_lock){+.+...}, at: [<c10e41c9>] __d_path+0x39/0x80
[ 384.711037] #2: (vfsmount_lock){++++..}, at: [<c10e8500>] vfsmount_lock_local_lock+0x0/0x60
[ 384.711037] #3: (&serio->lock){-.-...}, at: [<c12ddb68>] serio_interrupt+0x28/0x80
[ 384.711037] #4: (&(&dev->event_lock)->rlock){-.-...}, at: [<c12e053f>] input_event+0x3f/0x70
[ 384.711037] #5: (rcu_read_lock){.+.+..}, at: [<c12dfe30>] input_pass_event+0x0/0x1c0
[ 384.711037] #6: (sysrq_key_table_lock){-.-...}, at: [<c124c348>] __handle_sysrq+0x18/0x110
[ 384.711037] #7: (tasklist_lock){.?.?..}, at: [<c10701a6>] debug_show_all_locks+0x36/0x1d0
[ 384.711037]
(I think #3 to #7 are caused by pressing sysrq key.)
Complete log is at http://I-love.SAKURA.ne.jp/tmp/dmesg-2.6.38.txt
Regards.
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