Changeset 44847 in vbox for trunk/src/VBox

Timestamp:

Feb 27, 2013 6:47:11 PM (12 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

83996

Message:

TMR3UtcNow: Get stable offVirtualSync and offVirtualSyncGivenUp values.

File:

• trunk/src/VBox/VMM/VMMR3/TM.cpp (modified) (1 diff)

trunk/src/VBox/VMM/VMMR3/TM.cpp

@@ -2620 +2620 @@
 VMMR3_INT_DECL(PRTTIMESPEC) TMR3UtcNow(PVM pVM, PRTTIMESPEC pTime)
 {
+    /* Get a stable set of VirtualSync parameters before querying UTC. */
+    uint64_t offVirtualSync;
+    uint64_t offVirtualSyncGivenUp;
+    do
+    {
+        offVirtualSync        = ASMAtomicReadU64(&pVM->tm.s.offVirtualSync);
+        offVirtualSyncGivenUp = ASMAtomicReadU64((uint64_t volatile *)&pVM->tm.s.offVirtualSyncGivenUp);
+    } while (ASMAtomicReadU64(&pVM->tm.s.offVirtualSync) != offVirtualSync);
+
+    Assert(offVirtualSync >= offVirtualSyncGivenUp);
+    uint64_t const offLag = offVirtualSync - offVirtualSyncGivenUp;
+
     RTTimeNow(pTime);
-    RTTimeSpecSubNano(pTime, ASMAtomicReadU64(&pVM->tm.s.offVirtualSync) - ASMAtomicReadU64((uint64_t volatile *)&pVM->tm.s.offVirtualSyncGivenUp));
+    RTTimeSpecSubNano(pTime, offLag);
     RTTimeSpecAddNano(pTime, pVM->tm.s.offUTC);
     return pTime;