mem: Split port retry for all different packet classes

This patch fixes a long-standing isue with the port flow
control. Before this patch the retry mechanism was shared between all
different packet classes. As a result, a snoop response could get
stuck behind a request waiting for a retry, even if the send/recv
functions were split. This caused message-dependent deadlocks in
stress-test scenarios.

The patch splits the retry into one per packet (message) class. Thus,
sendTimingReq has a corresponding recvReqRetry, sendTimingResp has
recvRespRetry etc. Most of the changes to the code involve simply
clarifying what type of request a specific object was accepting.

The biggest change in functionality is in the cache downstream packet
queue, facing the memory. This queue was shared by requests and snoop
responses, and it is now split into two queues, each with their own
flow control, but the same physical MasterPort. These changes fixes
the previously seen deadlocks.

2 files changed, 3 insertions, 3 deletions

diff --git a/src/cpu/testers/traffic_gen/traffic_gen.cc b/src/cpu/testers/traffic_gen/traffic_gen.cc
index 9eee7a119..e4759512d 100644
--- a/src/cpu/testers/traffic_gen/traffic_gen.cc
+++ b/src/cpu/testers/traffic_gen/traffic_gen.cc
@@ -476,7 +476,7 @@ TrafficGen::enterState(uint32_t newState)
 }
 
 void
-TrafficGen::recvRetry()
+TrafficGen::recvReqRetry()
 {
     assert(retryPkt != NULL);
 
diff --git a/src/cpu/testers/traffic_gen/traffic_gen.hh b/src/cpu/testers/traffic_gen/traffic_gen.hh
index b9081b1d4..eb9f6541d 100644
--- a/src/cpu/testers/traffic_gen/traffic_gen.hh
+++ b/src/cpu/testers/traffic_gen/traffic_gen.hh
@@ -91,7 +91,7 @@ class TrafficGen : public MemObject
      * Receive a retry from the neighbouring port and attempt to
      * resend the waiting packet.
      */
-    void recvRetry();
+    void recvReqRetry();
 
     /** Struct to represent a probabilistic transition during parsing. */
     struct Transition {
@@ -148,7 +148,7 @@ class TrafficGen : public MemObject
 
       protected:
 
-        void recvRetry() { trafficGen.recvRetry(); }
+        void recvReqRetry() { trafficGen.recvReqRetry(); }
 
         bool recvTimingResp(PacketPtr pkt);