On 5/15/20 1:21 AM, Qian Cai wrote:
Lockdep is screwed here in next-20200514 due to "BUG: MAX_LOCKDEP_ENTRIES too low". One of the traces below pointed to this linux-next commit, 8c8e824d4ef0 watch_queue: Introduce a non-repeating system-unique superblock ID which was accidentally just showed up in next-20200514 along with, 46896d79c514 watch_queue: Add superblock notifications I did have here, CONFIG_SB_NOTIFICATIONS=y CONFIG_MOUNT_NOTIFICATIONS=y CONFIG_FSINFO=y While MAX_LOCKDEP_ENTRIES is 32768, I noticed there is one type of lock had a lot along, # grep 'type->s_umount_key’ /proc/lockdep_chains | wc -l 6979
The lock_list table entries are for tracking a lock's forward and backward dependencies. The lockdep_chains isn't the right lockdep file to look at. Instead, check the lockdep files for entries with the maximum BD (backward dependency) + FD (forward dependency). That will give you a better view of which locks are consuming most of the lock_list entries. Also take a look at lockdep_stats for an overall view of how much various table entries are being consumed.
Cheers, Longman
