On 14-09-01 11:36 AM, Christoph Hellwig wrote:
--- a/drivers/scsi/scsi_debug.c 2014-08-26 13:24:51.646948507 -0400 +++ b/drivers/scsi/scsi_debug.c 2014-08-30 18:04:54.589226679 -0400 @@ -2743,6 +2743,13 @@ static int stop_queued_cmnd(struct scsi_ if (test_bit(k, queued_in_use_bm)) { sqcp = &queued_arr[k]; if (cmnd == sqcp->a_cmnd) { + devip = (struct sdebug_dev_info *) + cmnd->device->hostdata; + if (devip) + atomic_dec(&devip->num_in_q); + sqcp->a_cmnd = NULL;Why would the hostdata every be NULL here? We should never call ->slave_destroy on a device that has outstanding commands.
To your first question, perhaps it could not be. In the scsi_debug driver almost all uses of 'devip' check for NULL, so it may not always have been true. 'rmmod scsi_debug' would lead to scsi_debug_exit() being called and that called stop_all_queued() which deadlocked with a command completion, or worse command commencement. scsi_debug_exit() looks a bit racy: the first thing it does is stop_all_queued() but has anything been done to stop new commands being issued? Later scsi_debug_exit() brings down the hosts. This patch is primarily a bug fix for the lk 3.17 series and the code you highlight was simply moved from being under a lock to outside that lock. I didn't want to be too creative, it's too easy to slip up and upset the management. Enhancements could be sent to your drivers-for-3.18 tree. Rob Elliott already has a few in mind, to improve performance. Removing all 'devip' NULL checks would also improve performance, and readability. Doug Gilbert -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
