replace the unnecessary checks in probe with potential error assetions

cache/coherence.hpp

@@ -163,16 +163,10 @@ class OuterCohPortT : public OPUC<Policy, EnMT, Extra...>
     CMDataBase *data = nullptr;
 
     if constexpr (EnMT) {
-      while(true) {
-        hit = cache->hit(addr, &ai, &s, &w, XactPrio::probe, true);
-        if(hit) {
-          std::tie(meta, data) = cache->access_line(ai, s, w); meta->lock();
-          if(!meta->match(addr)) { // cache line is invalidated by transactions with higher priority
-            meta->unlock(); meta = nullptr; data = nullptr;
-            cache->reset_mt_state(ai, s, XactPrio::probe); continue; // redo the hit check
-          }
-        }
-        break;
+      hit = cache->hit(addr, &ai, &s, &w, XactPrio::probe, true);
+      if(hit) {
+        std::tie(meta, data) = cache->access_line(ai, s, w); meta->lock();
+        assert(meta->match(addr)); // probe is the highest priority and nobody should intercept a probe after it locked a set
       }
     } else {
       hit = cache->hit(addr, &ai, &s, &w);
@@ -187,11 +181,9 @@ class OuterCohPortT : public OPUC<Policy, EnMT, Extra...>
         if(pwb) cache->hook_write(addr, ai, s, w, true, false, meta, data, delay);
       }
 
-      // writeback if dirty
-      if((writeback = Policy::probe_need_writeback(outer_cmd, meta))) {
-        if(data_outer) data_outer->copy(data);
-      }
-      if constexpr (EnMT) meta_outer->lock();
+      // now we should be able to safely operate on the cache line
+      if constexpr (EnMT) {assert(meta->match(addr)); meta_outer->lock(); }
+      if((writeback = Policy::probe_need_writeback(outer_cmd, meta))) { if(data_outer) data_outer->copy(data); } // writeback if dirty
       Policy::meta_after_probe(outer_cmd, meta, meta_outer, coh_id, writeback); // alway update meta
       cache->hook_manage(addr, ai, s, w, hit, coh::is_evict(outer_cmd), writeback, meta, data, delay);
       if constexpr (EnMT) { meta_outer->unlock(); meta->unlock(); cache->reset_mt_state(ai, s, XactPrio::probe); }
@@ -402,7 +394,7 @@ class InnerCohPortT : public IPUC<Policy, EnMT, Extra...>
     auto [valid, forward, meta, ai, s] = pending_xact.read(addr, outer_cmd.id);
     if(valid) {
       // avoid probe to the same cache line happens between a grant and a finish,
-      // unlock the cache line until a finish is received (only needed for coherent inner cache)
+      // do not unlock the cache line until a finish is received (only needed for coherent inner cache)
       if constexpr (EnMT) { meta->unlock(); cache->reset_mt_state(ai, s, XactPrio::acquire); }
       pending_xact.remove(addr, outer_cmd.id);
       if(forward) outer->finish_req(addr);