3.16.39-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Nicholas Bellinger <[email protected]> commit 5e2c956b8aa24d4f33ff7afef92d409eed164746 upstream. During transport_generic_free_cmd() with a concurrent TMR ABORT_TASK and shutdown CMD_T_FABRIC_STOP bit set, the caller will be blocked on se_cmd->cmd_wait_stop completion until the final kref_put() -> target_release_cmd_kref() has been invoked to call complete(). However, when ABORT_TASK is completed with FUNCTION_COMPLETE in core_tmr_abort_task(), the aborted se_cmd will have already been removed from se_sess->sess_cmd_list via list_del_init(). This results in target_release_cmd_kref() hitting the legacy list_empty() == true check, invoking ->release_cmd() but skipping complete() to wakeup se_cmd->cmd_wait_stop blocked earlier in transport_generic_free_cmd() code. To address this bug, it's safe to go ahead and drop the original list_empty() check so that fabric_stop invokes the complete() as expected, since list_del_init() can safely be used on a empty list. Cc: Mike Christie <[email protected]> Cc: Quinn Tran <[email protected]> Cc: Himanshu Madhani <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Hannes Reinecke <[email protected]> Tested-by: Nicholas Bellinger <[email protected]> Signed-off-by: Nicholas Bellinger <[email protected]> [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <[email protected]> --- drivers/target/target_core_transport.c | 6 ------ 1 file changed, 6 deletions(-) --- a/drivers/target/target_core_transport.c +++ b/drivers/target/target_core_transport.c @@ -2455,12 +2455,6 @@ static void target_release_cmd_kref(stru struct se_session *se_sess = se_cmd->se_sess; bool fabric_stop; - if (list_empty(&se_cmd->se_cmd_list)) { - spin_unlock(&se_sess->sess_cmd_lock); - target_free_cmd_mem(se_cmd); - se_cmd->se_tfo->release_cmd(se_cmd); - return; - } spin_lock(&se_cmd->t_state_lock); fabric_stop = (se_cmd->transport_state & CMD_T_FABRIC_STOP);
