Merge pull request #104 from basho/mv-prefetch-race

correct prefetch race condition.
basho · Mar 13, 2014 · 639f69c · 639f69c
2 parents c91408c + 0af027d
commit 639f69c
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Showing 2 changed files with 10 additions and 4 deletions.
diff --git a/c_src/eleveldb.cc b/c_src/eleveldb.cc
@@ -2,7 +2,7 @@
 //
 // eleveldb: Erlang Wrapper for LevelDB (http://code.google.com/p/leveldb/)
 //
-// Copyright (c) 2011-2013 Basho Technologies, Inc. All Rights Reserved.
+// Copyright (c) 2011-2014 Basho Technologies, Inc. All Rights Reserved.
 //
 // This file is provided to you under the Apache License,
 // Version 2.0 (the "License"); you may not use this file
@@ -738,7 +738,7 @@ async_iterator_move(
     const ERL_NIF_TERM& action_or_target = argv[2];
     ERL_NIF_TERM ret_term;
 
-    bool submit_new_request(true);
+    bool submit_new_request(true), prefetch_state;
 
     ReferencePtr<ItrObject> itr_ptr;
 
@@ -768,6 +768,11 @@ async_iterator_move(
     // debug syslog(LOG_ERR, "move state: %d, %d, %d",
     //              action, itr_ptr->m_Iter->m_PrefetchStarted, itr_ptr->m_Iter->m_HandoffAtomic);
 
+    // must set this BEFORE call to compare_and_swap ... or have potential
+    //  for an "extra" message coming out of prefetch
+    prefetch_state = itr_ptr->m_Iter->m_PrefetchStarted;
+    itr_ptr->m_Iter->m_PrefetchStarted =  prefetch_state && (eleveldb::MoveTask::PREFETCH_STOP != action );
+
     //
     // Three situations:
     //  #1 not a PREFETCH next call
@@ -802,7 +807,7 @@ async_iterator_move(
         // leave m_HandoffAtomic as 1 so first response is via message
 
         // is this truly a wait for prefetch ... or actually the first prefetch request
-        if (!itr_ptr->m_Iter->m_PrefetchStarted)
+        if (!prefetch_state)
         {
             submit_new_request=true;
             itr_ptr->ReleaseReuseMove();
@@ -814,6 +819,7 @@ async_iterator_move(
             submit_new_request=false;
         }   // else
 
+        // redundant ... but clarifying where it really belongs in logic pattern
         itr_ptr->m_Iter->m_PrefetchStarted=(eleveldb::MoveTask::PREFETCH_STOP != action );
     }   // else if
 

diff --git a/test/eleveldb_schema_tests.erl b/test/eleveldb_schema_tests.erl
@@ -13,7 +13,7 @@ basic_schema_test() ->
         ["../priv/eleveldb.schema"], [], context(), predefined_schema()),
 
     cuttlefish_unit:assert_config(Config, "eleveldb.data_root", "./data/leveldb"),
-    cuttlefish_unit:assert_config(Config, "eleveldb.total_leveldb_mem_percent", 80),
+    cuttlefish_unit:assert_config(Config, "eleveldb.total_leveldb_mem_percent", 70),
     cuttlefish_unit:assert_not_configured(Config, "eleveldb.total_leveldb_mem"),
     cuttlefish_unit:assert_config(Config, "eleveldb.sync", false),
     cuttlefish_unit:assert_config(Config, "eleveldb.limited_developer_mem", false),