On 10/7/20 9:53 AM, Maurizio Lombardi wrote: > The iscsit_release_commands_from_conn() function does the following > operations: > > 1) locks the cmd_lock spinlock > 2) Scans the list of commands and sets the CMD_T_FABRIC_STOP flag > 3) Releases the cmd_lock spinlock > 4) Rescans the list again and clears the i_conn_node link of each command > > If an abort task timer is fired between 3) and 4), it will find > the CMD_T_FABRIC_STOP flag set and won't call list_del_init(); > therefore it may end up calling __iscsit_free_cmd() with a > non-empty i_conn_node list, thus triggering the warning. > > Considering that: > > - we expect list_del_init() to be executed by > iscsit_release_commands_from_conn() when the CMD_T_FABRIC_STOP is set. > - iscsit_aborted_task() is the only function that calls __iscsit_free_cmd() > directly, while all the other functions call iscsit_free_cmd(). > - the warning in __iscsit_free_cmd() is a duplicate (the same warning > can be found in iscsit_free_cmd(). > For iscsi, what does the last put on the cmd for a successful abort. Ignore this conn stop case. If we abort a command successfully, the abort path does: target_handle_abort -> transport_cmd_check_stop_to_fabric -> lio_check_stop_free -> target_put_sess_cmd When we create the cmd we do transport_init_se_cmd and that sets the refcount=1. We do target_get_sess_cmd with ack_kref=true so that sets refcount=2. On the abort completion path, target_handle_abort does target_put_sess_cmd (refcount=1 after), check_stop_free ends up doing a put (refcount=0 after). If we free the cmd from the abort path, then for your conn stop plus abort race case, could we do: 1. thread1 runs iscsit_release_commands_from_conn and sets CMD_T_FABRIC_STOP. 2. thread2 runs iscsit_aborted_task and then does __iscsit_free_cmd. It then returns from the aborted_task callout and we finish target_handle_abort and do: target_handle_abort -> transport_cmd_check_stop_to_fabric -> lio_check_stop_free -> target_put_sess_cmd The cmd is now freed. 3. thread1 now finishes iscsit_release_commands_from_conn and runs iscsit_free_cmd while accessing a command we just released.
