bus/vmbus: debug subchannel setup

Add more instrumentation to subchannel setup to help diagnose
startup issues.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>

diff --git a/drivers/bus/vmbus/linux/vmbus_uio.c b/drivers/bus/vmbus/linux/vmbus_uio.c
index 38df4d7..09f7efd 100644 (file)
--- a/drivers/bus/vmbus/linux/vmbus_uio.c
+++ b/drivers/bus/vmbus/linux/vmbus_uio.c
@@ -357,19 +357,25 @@ int vmbus_uio_get_subchan(struct vmbus_channel *primary,
                        continue;
                }
 
-               if (!vmbus_isnew_subchannel(primary, relid))
-                       continue;       /* Already know about you */
+               if (!vmbus_isnew_subchannel(primary, relid)) {
+                       VMBUS_LOG(DEBUG, "skip already found channel: %lu",
+                                 relid);
+                       continue;
+               }
 
-               if (!vmbus_uio_ring_present(dev, relid))
-                       continue;       /* Ring may not be ready yet */
+               if (!vmbus_uio_ring_present(dev, relid)) {
+                       VMBUS_LOG(DEBUG, "ring mmap not found (yet) for: %lu",
+                                 relid);
+                       continue;
+               }
 
                snprintf(subchan_path, sizeof(subchan_path), "%s/%lu",
                         chan_path, relid);
                err = vmbus_uio_sysfs_read(subchan_path, "subchannel_id",
                                           &subid, UINT16_MAX);
                if (err) {
-                       VMBUS_LOG(NOTICE, "invalid subchannel id %lu",
-                                 subid);
+                       VMBUS_LOG(NOTICE, "no subchannel_id in %s:%s",
+                                 subchan_path, strerror(-err));
                        goto fail;
                }
 
@@ -379,14 +385,14 @@ int vmbus_uio_get_subchan(struct vmbus_channel *primary,
                err = vmbus_uio_sysfs_read(subchan_path, "monitor_id",
                                           &monid, UINT8_MAX);
                if (err) {
-                       VMBUS_LOG(NOTICE, "invalid monitor id %lu",
-                                 monid);
+                       VMBUS_LOG(NOTICE, "no monitor_id in %s:%s",
+                                 subchan_path, strerror(-err));
                        goto fail;
                }
 
                err = vmbus_chan_create(dev, relid, subid, monid, subchan);
                if (err) {
-                       VMBUS_LOG(NOTICE, "subchannel setup failed");
+                       VMBUS_LOG(ERR, "subchannel setup failed");
                        goto fail;
                }
                break;