argo: warn sendv() caller when ring is full

In its current state, if the destination ring is full, sendv()
will requeue the message and return the rc of pending_requeue(),
which will return 0 on success. This prevents the caller from
distinguishing the difference between a successful write and a
message that needs to be resent at a later time.

Instead, capture the -EAGAIN value returned from ringbuf_insert()
and *only* overwrite it if the rc of pending_requeue() is non-zero.
This allows the caller to make intelligent decisions on -EAGAIN and
still be alerted if the pending message fails to requeue.

Signed-off-by: Nicholas Tsirakis <tsirakisn@ainfosec.com>
Reviewed-by: Christopher Clark <christopher.w.clark@gmail.com>
master commit: 480800c76969b38f13b6909eb679b23571417538
master date: 2019-06-11 20:27:28 +0100

diff --git a/xen/common/argo.c b/xen/common/argo.c
index 13052b923949ab2078930d984aef9745c0bf3932..2f874a570da1a6867560d3cdabcf214c770f25fa 100644 (file)
--- a/xen/common/argo.c
+++ b/xen/common/argo.c
@@ -2048,9 +2048,13 @@ sendv(struct domain *src_d, xen_argo_addr_t *src_addr,
                              message_type, &len);
         if ( ret == -EAGAIN )
         {
+            int rc;
+
             argo_dprintk("argo_ringbuf_sendv failed, EAGAIN\n");
             /* requeue to issue a notification when space is there */
-            ret = pending_requeue(dst_d, ring_info, src_id.domain_id, len);
+            rc = pending_requeue(dst_d, ring_info, src_id.domain_id, len);
+            if ( rc )
+                ret = rc;
         }
 
         spin_unlock(&ring_info->L3_lock);