bitkeeper revision 1.1209 (421346f9xbQDgRDaxkDUGy8ppyT1UQ)

fix debug race condition on tap.

signed-off-by: akw27@cl.cam.ac.uk

BitKeeper/etc/logging_ok

@@ -1,6 +1,7 @@
 ach61@boulderdash.cl.cam.ac.uk
 ach61@labyrinth.cl.cam.ac.uk
 ach61@soar.cl.cam.ac.uk
+akw27@arcadians.cl.cam.ac.uk
 akw27@boulderdash.cl.cam.ac.uk
 akw27@labyrinth.cl.cam.ac.uk
 akw27@plucky.localdomain

linux-2.6.10-xen-sparse/drivers/xen/blktap/blktap_datapath.c

@@ -456,13 +456,18 @@ void print_vm_ring_idxs(void)
     WPRINTK("FE Rings: \n---------\n");
     for ( i = 0; i < 50; i++) { 
         blkif = blkif_find_by_handle((domid_t)i, 0);
-        if (blkif != NULL)
-            WPRINTK("%2d: req_cons: %2d, rsp_prod_prv: %2d "
-                "| req_prod: %2d, rsp_prod: %2d\n", i, 
-                blkif->blk_ring.req_cons,
-                blkif->blk_ring.rsp_prod_pvt,
-                blkif->blk_ring.sring->req_prod,
-                blkif->blk_ring.sring->rsp_prod);
+        if (blkif != NULL) {
+            if (blkif->blk_ring.sring != NULL) {
+                WPRINTK("%2d: req_cons: %2d, rsp_prod_prv: %2d "
+                    "| req_prod: %2d, rsp_prod: %2d\n", i, 
+                    blkif->blk_ring.req_cons,
+                    blkif->blk_ring.rsp_prod_pvt,
+                    blkif->blk_ring.sring->req_prod,
+                    blkif->blk_ring.sring->rsp_prod);
+            } else {
+                WPRINTK("%2d: [no device channel yet]\n", i);
+            }
+        }
     }
     if (blktap_be_ring.sring != NULL) {
         WPRINTK("BE Ring: \n--------\n");