On Wed, Jan 10, 2018 at 10:18:16AM -0800, Bart Van Assche wrote: > Several SCSI transport and LLD drivers surround code that does not > tolerate concurrent calls of .queuecommand() with scsi_target_block() / > scsi_target_unblock(). These last two functions use > blk_mq_quiesce_queue() / blk_mq_unquiesce_queue() for scsi-mq request > queues to prevent concurrent .queuecommand() calls. However, that is Actually blk_mq_quiesce_queue() is supposed to disable and drain dispatch, not for prevent concurrent .queuecommand() calls. > not sufficient to prevent .queuecommand() calls from scsi_send_eh_cmnd(). Given it is error handling, do we need to prevent the .queuecommand() call in scsi_send_eh_cmnd()? Could you share us what the actual issue observed is from user view? > Hence surround the .queuecommand() call from the SCSI error handler with > blk_start_wait_if_quiesced() / blk_finish_wait_if_quiesced(). > > Note: converting the .queuecommand() call in scsi_send_eh_cmnd() into > code that calls blk_get_request(), e.g. scsi_execute_req(), is not an > option since scsi_send_eh_cmnd() can be called if all requests are > allocated and if no requests will make progress without aborting any > of these requests. If we need to prevent the .queuecommand() in scsi_send_eh_cmnd(), what do you think of the approach by requeuing the EH command via scsi_mq_requeue_cmd()/scsi_requeue_cmd()? And the EH request will be dispatched finally when the queue becomes unquiesced or the STOPPED is cleared. -- Ming
