Draining fixes.

src/cpu/o3/cpu.cc:
    Handle draining properly when CPU isn't actually being used.
src/cpu/simple/atomic.cc:
    Be sure to set status properly when draining.
src/mem/bus.cc:
    Fix for draining.

--HG--
extra : convert_revision : d9796e6693e974f022159029fc9743c49a970c8f

src/cpu/o3/cpu.cc

@@ -819,6 +819,12 @@ unsigned int
 FullO3CPU<Impl>::drain(Event *drain_event)
 {
     DPRINTF(O3CPU, "Switching out\n");
+
+    // If the CPU isn't doing anything, then return immediately.
+    if (_status == Idle || _status == SwitchedOut) {
+        return 0;
+    }
+
     drainCount = 0;
     fetch.drain();
     decode.drain();

src/cpu/simple/atomic.cc

@@ -213,6 +213,9 @@ AtomicSimpleCPU::takeOverFrom(BaseCPU *oldCPU)
             break;
         }
     }
+    if (_status != Running) {
+        _status = Idle;
+    }
 }
 
 

src/mem/bus.cc

@@ -242,8 +242,11 @@ Bus::recvRetry(int id)
         }
     }
     //If we weren't able to drain before, we might be able to now.
-    if (drainEvent && retryList.size() == 0 && curTick >= tickNextIdle)
+    if (drainEvent && retryList.size() == 0 && curTick >= tickNextIdle) {
         drainEvent->process();
+        // Clear the drain event once we're done with it.
+        drainEvent = NULL;
+    }
 }
 
 Port *