Index: /trunk/src/VBox/Devices/Storage/DevAHCI.cpp
===================================================================
--- /trunk/src/VBox/Devices/Storage/DevAHCI.cpp	(revision 29440)
+++ /trunk/src/VBox/Devices/Storage/DevAHCI.cpp	(revision 29441)
@@ -5406,4 +5406,8 @@
                 ahciSendD2HFis(pAhciPort, pAhciPortTaskState, pAhciPortTaskState->cmdFis, true);
                 pAhciPort->aCachedTasks[pNotifierItem->iTask] = pAhciPortTaskState;
+#ifdef RT_STRICT
+                fXchg = ASMAtomicCmpXchgBool(&pAhciPortTaskState->fActive, false, true);
+                AssertMsg(fXchg, ("Task is not active\n"));
+#endif
                 return true;
             }
@@ -5412,4 +5416,8 @@
                 ahciFinishStorageDeviceReset(pAhciPort, pAhciPortTaskState);
                 pAhciPort->aCachedTasks[pNotifierItem->iTask] = pAhciPortTaskState;
+#ifdef RT_STRICT
+                fXchg = ASMAtomicCmpXchgBool(&pAhciPortTaskState->fActive, false, true);
+                AssertMsg(fXchg, ("Task is not active\n"));
+#endif
                 return true;
             }