From d1105a7417a983af1cc6fa4ea6a0657fa6413481 Mon Sep 17 00:00:00 2001

Message-Id: <d1105a7417a983af1cc6fa4ea6a0657fa6413481.1382534060.git.jdenemar@redhat.com>

From: Peter Krempa <pkrempa@redhat.com>

Date: Thu, 10 Oct 2013 13:56:31 +0200

Subject: [PATCH] qemu: monitor: Produce better errors on monitor hangup

https://bugzilla.redhat.com/show_bug.cgi?id=1001738

Change the monitor error code to add the ability to access the qemu log

file using a file descriptor so that we can dig in it for a more useful

error message. The error is now logged on monitor hangups and overwrites

a possible lesser error. A hangup on the monitor usualy means that qemu

has crashed and there's a significant chance it produced a useful error

message.

The functionality will be latent until the next patch.

(cherry picked from commit 90139a6236eb20a5cd2595af39ea11adae7d54de)

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

---

 src/qemu/qemu_monitor.c | 66 ++++++++++++++++++++++++++++++++++++++++++++-----

 1 file changed, 60 insertions(+), 6 deletions(-)

diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c

index 2eb536c..cf4f954 100644

--- a/src/qemu/qemu_monitor.c

+++ b/src/qemu/qemu_monitor.c

@@ -32,6 +32,8 @@

 #include "qemu_monitor.h"

 #include "qemu_monitor_text.h"

 #include "qemu_monitor_json.h"

+#include "qemu_domain.h"

+#include "qemu_process.h"

 #include "virerror.h"

 #include "viralloc.h"

 #include "virlog.h"

@@ -332,6 +334,35 @@ qemuMonitorOpenPty(const char *monitor)

 }

+/* Get a possible error from qemu's log. This function closes the

+ * corresponding log fd */

+static char *

+qemuMonitorGetErrorFromLog(qemuMonitorPtr mon)

+{

+    int len;

+    char *logbuf = NULL;

+    int orig_errno = errno;

+

+    if (mon->logfd < 0)

+        return NULL;

+

+    if (VIR_ALLOC_N_QUIET(logbuf, 4096) < 0)

+        goto error;

+

+    if ((len = qemuProcessReadLog(mon->logfd, logbuf, 4096 - 1, 0, true)) <= 0)

+        goto error;

+

+cleanup:

+    errno = orig_errno;

+    VIR_FORCE_CLOSE(mon->logfd);

+    return logbuf;

+

+error:

+    VIR_FREE(logbuf);

+    goto cleanup;

+}

+

+

 /* This method processes data that has been received

  * from the monitor. Looking for async events and

  * replies/errors.

@@ -565,6 +596,7 @@ qemuMonitorIO(int watch, int fd, int events, void *opaque) {

     qemuMonitorPtr mon = opaque;

     bool error = false;

     bool eof = false;

+    bool hangup = false;

     virObjectRef(mon);

@@ -615,12 +647,14 @@ qemuMonitorIO(int watch, int fd, int events, void *opaque) {

             }

         }

-        if (!error &&

-            events & VIR_EVENT_HANDLE_HANGUP) {

-            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",

-                           _("End of file from monitor"));

-            eof = true;

-            events &= ~VIR_EVENT_HANDLE_HANGUP;

+        if (events & VIR_EVENT_HANDLE_HANGUP) {

+            hangup = true;

+            if (!error) {

+                virReportError(VIR_ERR_INTERNAL_ERROR, "%s",

+                               _("End of file from monitor"));

+                eof = true;

+                events &= ~VIR_EVENT_HANDLE_HANGUP;

+            }

         }

         if (!error && !eof &&

@@ -639,6 +673,26 @@ qemuMonitorIO(int watch, int fd, int events, void *opaque) {

     }

     if (error || eof) {

+        if (hangup) {

+            /* Check if an error message from qemu is available and if so, use

+             * it to overwrite the actual message. It's done only in early

+             * startup phases where the message from qemu is certainly more

+             * interesting than a "connection reset by peer" message.

+             */

+            char *qemuMessage;

+

+            if ((qemuMessage = qemuMonitorGetErrorFromLog(mon))) {

+                virReportError(VIR_ERR_INTERNAL_ERROR,

+                               _("early end of file from monitor: "

+                                 "possible problem:\n%s"),

+                               qemuMessage);

+                virCopyLastError(&mon->lastError);

+                virResetLastError();

+            }

+

+            VIR_FREE(qemuMessage);

+        }

+

         if (mon->lastError.code != VIR_ERR_OK) {

             /* Already have an error, so clear any new error */

             virResetLastError();

-- 

1.8.4