mem: Add predecessor to SenderState base class

This patch adds a predecessor field to the SenderState base class to
make the process of linking them up more uniform, and enable a
traversal of the stack without knowing the specific type of the
subclasses.

There are a number of simplifications done as part of changing the
SenderState, particularly in the RubyTest.

1 files changed, 2 insertions, 3 deletions

diff --git a/src/arch/x86/pagetable_walker.cc b/src/arch/x86/pagetable_walker.cc
index b096fbfe8..c768bb428 100644
--- a/src/arch/x86/pagetable_walker.cc
+++ b/src/arch/x86/pagetable_walker.cc
@@ -123,8 +123,7 @@ bool
 Walker::recvTimingResp(PacketPtr pkt)
 {
     WalkerSenderState * senderState =
-        dynamic_cast<WalkerSenderState *>(pkt->senderState);
-    pkt->senderState = senderState->saved;
+        dynamic_cast<WalkerSenderState *>(pkt->popSenderState());
     WalkerState * senderWalk = senderState->senderWalk;
     bool walkComplete = senderWalk->recvPacket(pkt);
     delete senderState;
@@ -169,7 +168,7 @@ Walker::recvRetry()
 
 bool Walker::sendTiming(WalkerState* sendingState, PacketPtr pkt)
 {
-    pkt->senderState = new WalkerSenderState(sendingState, pkt->senderState);
+    pkt->pushSenderState(new WalkerSenderState(sendingState));
     return port.sendTimingReq(pkt);
 }