diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index b0d93bf79978f..25faad7f8e617 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -5486,9 +5486,11 @@ static int schedule_resp(struct scsi_cmnd *cmnd, struct sdebug_dev_info *devip,
 				u64 d = ktime_get_boottime_ns() - ns_from_boot;
 
 				if (kt <= d) {	/* elapsed duration >= kt */
+					spin_lock_irqsave(&sqp->qc_lock, iflags);
 					sqcp->a_cmnd = NULL;
 					atomic_dec(&devip->num_in_q);
 					clear_bit(k, sqp->in_use_bm);
+					spin_unlock_irqrestore(&sqp->qc_lock, iflags);
 					if (new_sd_dp)
 						kfree(sd_dp);
 					/* call scsi_done() from this thread */