On 6/5/19 10:14 PM, 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 > not sufficient to prevent .queuecommand() calls from scsi_send_eh_cmnd(). > Hence surround the .queuecommand() call from the SCSI error handler with > code that avoids that .queuecommand() gets called in the quiesced state. > > Note: converting the .queuecommand() call in scsi_send_eh_cmnd() into > code that calls blk_get_request() + blk_execute_rq() is not an option > since scsi_send_eh_cmnd() must be able to make forward progress even > if all requests have been allocated. > Hmm. Have you actually observed this? Typically, scsi_target_block()/scsi_target_unblock() is called prior to invoking EH, to allow the system to settle and to guarantee that it's fully quiesced. Only then EH is started. Consequently, scsi_target_block()/scsi_target_unblock() really shouldn't be called during EH; we're essentially single-threaded at this point, so nothing else will be submitting command. Can you explain why you need this? Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking hare@xxxxxxx +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 21284 (AG Nürnberg)
