Problem with our error reporting is that the error object is a
thread local variable. That means if there's an error reported
within the I/O thread it gets logged and everything, but later
when the event loop aborts the stream it doesn't see the original
error. So we are left with some generic error. We can do better
if we copy the error message between the threads.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
---
 daemon/stream.c        | 18 ++++++++++++------
 src/util/virfdstream.c |  9 ++++++---
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/daemon/stream.c b/daemon/stream.c
index 1d5b50ad7..5077ac8b0 100644
--- a/daemon/stream.c
+++ b/daemon/stream.c
@@ -231,17 +231,23 @@ daemonStreamEvent(virStreamPtr st, int events, void *opaque)
         int ret;
         virNetMessagePtr msg;
         virNetMessageError rerr;
+        virErrorPtr origErr = virSaveLastError();
 
         memset(&rerr, 0, sizeof(rerr));
         stream->closed = true;
         virStreamEventRemoveCallback(stream->st);
         virStreamAbort(stream->st);
-        if (events & VIR_STREAM_EVENT_HANGUP)
-            virReportError(VIR_ERR_RPC,
-                           "%s", _("stream had unexpected termination"));
-        else
-            virReportError(VIR_ERR_RPC,
-                           "%s", _("stream had I/O failure"));
+        if (origErr && origErr->code != VIR_ERR_OK) {
+            virSetError(origErr);
+            virFreeError(origErr);
+        } else {
+            if (events & VIR_STREAM_EVENT_HANGUP)
+                virReportError(VIR_ERR_RPC,
+                               "%s", _("stream had unexpected termination"));
+            else
+                virReportError(VIR_ERR_RPC,
+                               "%s", _("stream had I/O failure"));
+        }
 
         msg = virNetMessageNew(false);
         if (!msg) {
diff --git a/src/util/virfdstream.c b/src/util/virfdstream.c
index bd2355d17..f54ba15ae 100644
--- a/src/util/virfdstream.c
+++ b/src/util/virfdstream.c
@@ -106,7 +106,7 @@ struct virFDStreamData {
     /* Thread data */
     virThreadPtr thread;
     virCond threadCond;
-    int threadErr;
+    virErrorPtr threadErr;
     bool threadQuit;
     bool threadAbort;
     bool threadDoRead;
@@ -123,6 +123,7 @@ virFDStreamDataDispose(void *obj)
     virFDStreamDataPtr fdst = obj;
 
     VIR_DEBUG("obj=%p", fdst);
+    virFreeError(fdst->threadErr);
     virFDStreamMsgQueueFree(&fdst->msg);
 }
 
@@ -312,8 +313,10 @@ static void virFDStreamEvent(int watch ATTRIBUTE_UNUSED,
         return;
     }
 
-    if (fdst->threadErr)
+    if (fdst->threadErr) {
         events |= VIR_STREAM_EVENT_ERROR;
+        virSetError(fdst->threadErr);
+    }
 
     cb = fdst->cb;
     cbopaque = fdst->opaque;
@@ -641,7 +644,7 @@ virFDStreamThread(void *opaque)
     return;
 
  error:
-    fdst->threadErr = errno;
+    fdst->threadErr = virSaveLastError();
     goto cleanup;
 }
 
-- 
2.13.0

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On 06/22/2017 08:30 AM, Michal Privoznik wrote:
> Problem with our error reporting is that the error object is a
> thread local variable. That means if there's an error reported
> within the I/O thread it gets logged and everything, but later
> when the event loop aborts the stream it doesn't see the original
> error. So we are left with some generic error. We can do better
> if we copy the error message between the threads.
> 
> Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
> ---
>  daemon/stream.c        | 18 ++++++++++++------
>  src/util/virfdstream.c |  9 ++++++---
>  2 files changed, 18 insertions(+), 9 deletions(-)
> 

Reviewed-by: John Ferlan <jferlan@redhat.com>

John

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