Index: /trunk/src/VBox/HostServices/GuestProperties/service.cpp
===================================================================
--- /trunk/src/VBox/HostServices/GuestProperties/service.cpp	(revision 29393)
+++ /trunk/src/VBox/HostServices/GuestProperties/service.cpp	(revision 29394)
@@ -97,11 +97,15 @@
 
     /** Are two properties equal? */
-    bool operator== (const Property &prop)
-    {
-        return (   mName == prop.mName
-                && mValue == prop.mValue
-                && mTimestamp == prop.mTimestamp
-                && mFlags == prop.mFlags
-               );
+    bool operator==(const Property &prop)
+    {
+        if (mTimestamp != prop.mTimestamp)
+            return false;
+        if (mFlags != prop.mFlags)
+            return false;
+        if (mName != prop.mName)
+            return false;
+        if (mValue != prop.mValue)
+            return false;
+        return true;
     }
 
@@ -164,4 +168,12 @@
     /** User data pointer to be supplied to the host callback function */
     void *mpvHostData;
+    /** The previous timestamp.
+     * This is used by getCurrentTimestamp() to decrease the chance of
+     * generating duplicate timestamps.  */
+    uint64_t mPrevTimestamp;
+    /** The number of consecutive timestamp adjustments that we've made.
+     * Together with mPrevTimestamp, this defines a set of obsolete timestamp
+     * values: {(mPrevTimestamp - mcTimestampAdjustments), ..., mPrevTimestamp} */
+    uint64_t mcTimestampAdjustments;
 
     /**
@@ -193,7 +205,10 @@
          *  - Matches the pszPatterns
          */
+        /** @todo r=bird: This incorrectly ASSUMES that mTimestamp is unique.
+         *  The timestamp resolution can be very coarse on windows for instance. */
         PropertyList::const_iterator it = mGuestNotifications.begin();
         for (;    it != mGuestNotifications.end()
-               && it->mTimestamp != u64Timestamp; ++it) {}
+               && it->mTimestamp != u64Timestamp; ++it)
+            {}
         if (it == mGuestNotifications.end())  /* Not found */
             it = mGuestNotifications.begin();
@@ -239,4 +254,6 @@
         , mpfnHostCallback(NULL)
         , mpvHostData(NULL)
+        , mPrevTimestamp(0)
+        , mcTimestampAdjustments(0)
     { }
 
@@ -319,4 +336,5 @@
 private:
     static DECLCALLBACK(int) reqThreadFn(RTTHREAD ThreadSelf, void *pvUser);
+    uint64_t getCurrentTimestamp(void);
     int validateName(const char *pszName, uint32_t cbName);
     int validateValue(const char *pszValue, uint32_t cbValue);
@@ -344,4 +362,29 @@
 
 /**
+ * Gets the current timestamp.
+ *
+ * Since the RTTimeNow resolution can be very coarse, this method takes some
+ * simple steps to try avoid returning the same timestamp for two consecutive
+ * calls.  Code like getOldNotification() more or less assumes unique
+ * timestamps.
+ *
+ * @returns Nanosecond timestamp.
+ */
+uint64_t Service::getCurrentTimestamp(void)
+{
+    RTTIMESPEC time;
+    uint64_t u64NanoTS = RTTimeSpecGetNano(RTTimeNow(&time));
+    if (mPrevTimestamp - u64NanoTS > mcTimestampAdjustments)
+        mcTimestampAdjustments = 0;
+    else
+    {
+        mcTimestampAdjustments++;
+        u64NanoTS = mPrevTimestamp + 1;
+    }
+    this->mPrevTimestamp = u64NanoTS;
+    return u64NanoTS;
+}
+
+/**
  * Check that a string fits our criteria for a property name.
  *
@@ -572,6 +615,5 @@
     uint32_t cchFlags = 0;
     uint32_t fFlags = NILFLAG;
-    RTTIMESPEC time;
-    uint64_t u64TimeNano = RTTimeSpecGetNano(RTTimeNow(&time));
+    uint64_t u64TimeNano = getCurrentTimestamp();
 
     LogFlowThisFunc(("\n"));
@@ -702,6 +744,5 @@
         if (rc == VINF_SUCCESS && found)
         {
-            RTTIMESPEC time;
-            uint64_t u64Timestamp = RTTimeSpecGetNano(RTTimeNow(&time));
+            uint64_t u64Timestamp = getCurrentTimestamp();
             mProperties.erase(it);
             // if (isGuest)  /* Notify the host even for properties that the host
@@ -808,26 +849,25 @@
                                         Property *pProp)
 {
-    int rc = VINF_SUCCESS;
-    bool warn = false;
-
     /* We count backwards, as the guest should normally be querying the
      * most recent events. */
+    int rc = VWRN_NOT_FOUND;
     PropertyList::reverse_iterator it = mGuestNotifications.rbegin();
-    for (; it->mTimestamp != u64Timestamp && it != mGuestNotifications.rend();
-         ++it) {}
-    /* Warn if the timestamp was not found. */
-    if (it->mTimestamp != u64Timestamp)
-        warn = true;
+    for (; it != mGuestNotifications.rend(); ++it)
+        if (it->mTimestamp == u64Timestamp)
+        {
+            rc = VINF_SUCCESS;
+            break;
+        }
+
     /* Now look for an event matching the patterns supplied.  The base()
      * member conveniently points to the following element. */
     PropertyList::iterator base = it.base();
-    for (; !base->Matches(pszPatterns) && base != mGuestNotifications.end();
-         ++base) {}
-    if (RT_SUCCESS(rc) && base != mGuestNotifications.end())
-        *pProp = *base;
-    else if (RT_SUCCESS(rc))
-        *pProp = Property();
-    if (warn)
-        rc = VWRN_NOT_FOUND;
+    for (; base != mGuestNotifications.end(); ++base)
+        if (base->Matches(pszPatterns))
+        {
+            *pProp = *base;
+            return rc;
+        }
+    *pProp = Property();
     return rc;
 }
Index: /trunk/src/VBox/HostServices/GuestProperties/testcase/tstGuestPropSvc.cpp
===================================================================
--- /trunk/src/VBox/HostServices/GuestProperties/testcase/tstGuestPropSvc.cpp	(revision 29393)
+++ /trunk/src/VBox/HostServices/GuestProperties/testcase/tstGuestPropSvc.cpp	(revision 29394)
@@ -727,5 +727,5 @@
     int rc = VINF_SUCCESS;
     VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
-    char chBuffer[MAX_NAME_LEN + MAX_VALUE_LEN + MAX_FLAGS_LEN];
+    char achBuffer[MAX_NAME_LEN + MAX_VALUE_LEN + MAX_FLAGS_LEN];
     static char szPattern[] = "";
 
@@ -739,5 +739,5 @@
     paParms[0].setPointer ((void *) szPattern, sizeof(szPattern));
     paParms[1].setUInt64 (u64Timestamp);
-    paParms[2].setPointer ((void *) chBuffer, getNotifications[0].cchBuffer - 1);
+    paParms[2].setPointer ((void *) achBuffer, getNotifications[0].cchBuffer - 1);
     pTable->pfnCall(pTable->pvService, &callHandle, 0, NULL,
                     GET_NOTIFICATION, 4, paParms);
@@ -760,5 +760,5 @@
         paParms[0].setPointer ((void *) szPattern, sizeof(szPattern));
         paParms[1].setUInt64 (u64Timestamp);
-        paParms[2].setPointer ((void *) chBuffer, sizeof(chBuffer));
+        paParms[2].setPointer ((void *) achBuffer, sizeof(achBuffer));
         pTable->pfnCall(pTable->pvService, &callHandle, 0, NULL,
                         GET_NOTIFICATION, 4, paParms);
@@ -768,9 +768,9 @@
             || RT_FAILURE(paParms[3].getUInt32 (&u32Size))
             || u32Size != getNotifications[i].cchBuffer
-            || memcmp(chBuffer, getNotifications[i].pchBuffer, u32Size) != 0
+            || memcmp(achBuffer, getNotifications[i].pchBuffer, u32Size) != 0
            )
         {
-            RTPrintf("Failed to get notification for property '%s'.\n",
-                     getNotifications[i].pchBuffer);
+            RTPrintf("Failed to get notification for property '%s' (rc=%Rrc).\n",
+                     getNotifications[i].pchBuffer, rc);
             rc = VERR_UNRESOLVED_ERROR;
         }