mem: Fix WriteLineReq fill behaviour

This patch fixes issues in the interactions between deferred snoops
and WriteLineReq. More specifically, the patch addresses an issue
where deferred snoops caused assertion failures when being serviced on
the arrival of an InvalidateResp. The response packet was perceived to
be invalidating, when actually it is not for the cache that sent out
the original invalidation request.

diff --git a/src/mem/cache/cache.cc b/src/mem/cache/cache.cc
index 5ca17b88d9ddbf0a6ff347799c9c9115585d9cb9..fe715fa6dfd0acd04c2a88f178f700583a9b9c65 100644 (file)
--- a/src/mem/cache/cache.cc
+++ b/src/mem/cache/cache.cc
@@ -1228,7 +1228,7 @@ Cache::recvTimingResp(PacketPtr pkt)
 
     // allow invalidation responses originating from write-line
     // requests to be discarded
-    bool discard_invalidate = false;
+    bool is_invalidate = pkt->isInvalidate();
 
     // First offset for critical word first calculations
     int initial_offset = initial_tgt->pkt->getOffset(blkSize);
@@ -1271,7 +1271,7 @@ Cache::recvTimingResp(PacketPtr pkt)
                 // treat as a fill, and discard the invalidation
                 // response
                 is_fill = true;
-                discard_invalidate = true;
+                is_invalidate = false;
             }
 
             if (is_fill) {
@@ -1327,7 +1327,7 @@ Cache::recvTimingResp(PacketPtr pkt)
             if (is_error)
                 tgt_pkt->copyError(pkt);
             if (tgt_pkt->cmd == MemCmd::ReadResp &&
-                (pkt->isInvalidate() || mshr->hasPostInvalidate())) {
+                (is_invalidate || mshr->hasPostInvalidate())) {
                 // If intermediate cache got ReadRespWithInvalidate,
                 // propagate that.  Response should not have
                 // isInvalidate() set otherwise.
@@ -1353,7 +1353,7 @@ Cache::recvTimingResp(PacketPtr pkt)
             assert(!is_error);
             // response to snoop request
             DPRINTF(Cache, "processing deferred snoop...\n");
-            assert(!(pkt->isInvalidate() && !mshr->hasPostInvalidate()));
+            assert(!(is_invalidate && !mshr->hasPostInvalidate()));
             handleSnoop(tgt_pkt, blk, true, true, mshr->hasPostInvalidate());
             break;
 
@@ -1368,8 +1368,7 @@ Cache::recvTimingResp(PacketPtr pkt)
         // an invalidate response stemming from a write line request
         // should not invalidate the block, so check if the
         // invalidation should be discarded
-        if ((pkt->isInvalidate() || mshr->hasPostInvalidate()) &&
-            !discard_invalidate) {
+        if (is_invalidate || mshr->hasPostInvalidate()) {
             assert(blk != tempBlock);
             tags->invalidate(blk);
             blk->invalidate();