remote: Fix locking in stream APIs

Remote driver needs to make sure the driver lock is released before
entering client IO loop as that may block indefinitely in poll(). As a
direct consequence of not following this in stream APIs, tunneled
migration to a destination host which becomes non-responding may block
qemu driver. Luckily, if keepalive is turned for p2p migrations, both
remote and qemu drivers will get automagically unblocked after keepalive
timeout.
(cherry picked from commit 17f3be07)

src/remote/remote_driver.c

@@ -3882,12 +3882,14 @@ remoteStreamSend(virStreamPtr st,
     VIR_DEBUG("st=%p data=%p nbytes=%zu", st, data, nbytes);
     struct private_data *priv = st->conn->privateData;
     virNetClientStreamPtr privst = st->privateData;
-    int rv = -1;
-
-    remoteDriverLock(priv);
+    int rv;
 
     if (virNetClientStreamRaiseError(privst))
-        goto cleanup;
+        return -1;
+
+    remoteDriverLock(priv);
+    priv->localUses++;
+    remoteDriverUnlock(priv);
 
     rv = virNetClientStreamSendPacket(privst,
                                       priv->client,
@@ -3895,9 +3897,9 @@ remoteStreamSend(virStreamPtr st,
                                       data,
                                       nbytes);
 
-cleanup:
+    remoteDriverLock(priv);
+    priv->localUses--;
     remoteDriverUnlock(priv);
-
     return rv;
 }
 
@@ -3910,12 +3912,14 @@ remoteStreamRecv(virStreamPtr st,
     VIR_DEBUG("st=%p data=%p nbytes=%zu", st, data, nbytes);
     struct private_data *priv = st->conn->privateData;
     virNetClientStreamPtr privst = st->privateData;
-    int rv = -1;
-
-    remoteDriverLock(priv);
+    int rv;
 
     if (virNetClientStreamRaiseError(privst))
-        goto cleanup;
+        return -1;
+
+    remoteDriverLock(priv);
+    priv->localUses++;
+    remoteDriverUnlock(priv);
 
     rv = virNetClientStreamRecvPacket(privst,
                                       priv->client,
@@ -3925,9 +3929,9 @@ remoteStreamRecv(virStreamPtr st,
 
     VIR_DEBUG("Done %d", rv);
 
-cleanup:
+    remoteDriverLock(priv);
+    priv->localUses--;
     remoteDriverUnlock(priv);
-
     return rv;
 }
 
@@ -4044,12 +4048,18 @@ remoteStreamFinish(virStreamPtr st)
     if (virNetClientStreamRaiseError(privst))
         goto cleanup;
 
+    priv->localUses++;
+    remoteDriverUnlock(priv);
+
     ret = virNetClientStreamSendPacket(privst,
                                        priv->client,
                                        VIR_NET_OK,
                                        NULL,
                                        0);
 
+    remoteDriverLock(priv);
+    priv->localUses--;
+
 cleanup:
     virNetClientRemoveStream(priv->client, privst);
     virNetClientStreamFree(privst);
@@ -4073,12 +4083,18 @@ remoteStreamAbort(virStreamPtr st)
     if (virNetClientStreamRaiseError(privst))
         goto cleanup;
 
+    priv->localUses++;
+    remoteDriverUnlock(priv);
+
     ret = virNetClientStreamSendPacket(privst,
                                        priv->client,
                                        VIR_NET_ERROR,
                                        NULL,
                                        0);
 
+    remoteDriverLock(priv);
+    priv->localUses--;
+
 cleanup:
     virNetClientRemoveStream(priv->client, privst);
     virNetClientStreamFree(privst);