[LU-7593] umount vs tgt_last_rcvd_update deadlock

• Type: Bug
• Resolution: Fixed
• Priority: Major
• Fix Version/s: Lustre 2.9.0
• Labels: bgti patch
• Severity: 3
• Assignee: nasf (Inactive)
• Reporter: Andriy Skulysh

Description

tgt_client_del() and
ofd_commitrw_write->tgt_last_rcvd_update
take transaction and ted->ted_lcd_lock
in different order:

thread1:
osd_trans_start
tgt_client_data_update
tgt_client_del <<< mutex_lock(&ted->ted_lcd_lock);
ofd_obd_disconnect
class_disconnect_export_list
class_disconnect_exports
class_cleanup
...
sys_umount

thread2:
__mutex_lock_slowpath
mutex_lock <<< mutex_lock(&ted->ted_lcd_lock);
tgt_last_rcvd_update
tgt_txn_stop_cb
dt_txn_hook_stop
osd_trans_stop
ofd_trans_stop
ofd_commitrw_write
...
tgt_brw_write