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.

4 files changed, 6 insertions, 6 deletions

diff --git a/src/cpu/minor/fetch1.cc b/src/cpu/minor/fetch1.cc
index 79a5d0a78..567bd2ecc 100644
--- a/src/cpu/minor/fetch1.cc
+++ b/src/cpu/minor/fetch1.cc
@@ -417,7 +417,7 @@ Fetch1::recvTimingResp(PacketPtr response)
 }
 
 void
-Fetch1::recvRetry()
+Fetch1::recvReqRetry()
 {
     DPRINTF(Fetch, "recvRetry\n");
     assert(icacheState == IcacheNeedsRetry);
diff --git a/src/cpu/minor/fetch1.hh b/src/cpu/minor/fetch1.hh
index 29e10def5..d4a35c468 100644
--- a/src/cpu/minor/fetch1.hh
+++ b/src/cpu/minor/fetch1.hh
@@ -77,7 +77,7 @@ class Fetch1 : public Named
         bool recvTimingResp(PacketPtr pkt)
         { return fetch.recvTimingResp(pkt); }
 
-        void recvRetry() { fetch.recvRetry(); }
+        void recvReqRetry() { fetch.recvReqRetry(); }
     };
 
     /** Memory access queuing.
@@ -345,7 +345,7 @@ class Fetch1 : public Named
 
     /** Memory interface */
     virtual bool recvTimingResp(PacketPtr pkt);
-    virtual void recvRetry();
+    virtual void recvReqRetry();
 
   public:
     Fetch1(const std::string &name_,
diff --git a/src/cpu/minor/lsq.cc b/src/cpu/minor/lsq.cc
index 72873211b..06b6c5165 100644
--- a/src/cpu/minor/lsq.cc
+++ b/src/cpu/minor/lsq.cc
@@ -1235,7 +1235,7 @@ LSQ::recvTimingResp(PacketPtr response)
 }
 
 void
-LSQ::recvRetry()
+LSQ::recvReqRetry()
 {
     DPRINTF(MinorMem, "Received retry request\n");
 
diff --git a/src/cpu/minor/lsq.hh b/src/cpu/minor/lsq.hh
index 7936ae8f0..8a7d78216 100644
--- a/src/cpu/minor/lsq.hh
+++ b/src/cpu/minor/lsq.hh
@@ -101,7 +101,7 @@ class LSQ : public Named
         bool recvTimingResp(PacketPtr pkt)
         { return lsq.recvTimingResp(pkt); }
 
-        void recvRetry() { lsq.recvRetry(); }
+        void recvReqRetry() { lsq.recvReqRetry(); }
 
         void recvTimingSnoopReq(PacketPtr pkt)
         { return lsq.recvTimingSnoopReq(pkt); }
@@ -712,7 +712,7 @@ class LSQ : public Named
 
     /** Memory interface */
     bool recvTimingResp(PacketPtr pkt);
-    void recvRetry();
+    void recvReqRetry();
     void recvTimingSnoopReq(PacketPtr pkt);
 
     /** Return the raw-bindable port */