commit 9bcbd544fe68fd39e33c6acf09841130825f5b8b
author Zhenkai Zhu <zhenkai@cs.ucla.edu> Mon Dec 31 01:01:25 2012 -0800
committer Zhenkai Zhu <zhenkai@cs.ucla.edu> Mon Dec 31 01:01:25 2012 -0800
tree 815cd5cbaa8674c9e2dcfef9a44159e2c2601088
parent d8569c94812ad9c12ff8d1f55bfab15140029a00

lock for cache

include/object-db-file.h

diff --git a/include/object-db-file.h b/include/object-db-file.h
index b90bd91..dea8582 100644
--- a/include/object-db-file.h
+++ b/include/object-db-file.h
@@ -10,6 +10,7 @@
 #include <deque>
 #include <boost/thread/locks.hpp>
 #include <boost/lexical_cast.hpp>
+#include <boost/thread/shared_mutex.hpp>
 #include <boost/interprocess/sync/file_lock.hpp>
 #include <boost/interprocess/sync/sharable_lock.hpp>
 #include <boost/interprocess/sync/scoped_lock.hpp>
@@ -44,6 +45,9 @@
   typedef boost::interprocess::file_lock Filelock;
   typedef boost::interprocess::scoped_lock<Filelock> WriteLock;
   typedef boost::interprocess::sharable_lock<Filelock> ReadLock;
+  typedef boost::shared_mutex Mutex;
+  typedef boost::shared_lock<Mutex> SLock;
+  typedef boost::unique_lock<Mutex> ULock;
 
   ObjectDBFile(const string &filename);
   virtual ~ObjectDBFile(){}
@@ -121,6 +125,7 @@
   // If needed and time allows, we can have more complex cache
   #define CACHE_SIZE 10
   map<int, Bytes> m_dummyCache;
+  Mutex m_cacheMutex;
 };
 
 void inline

src/object-db-file.cpp

diff --git a/src/object-db-file.cpp b/src/object-db-file.cpp
index 02991a9..526ea4e 100644
--- a/src/object-db-file.cpp
+++ b/src/object-db-file.cpp
@@ -122,16 +122,20 @@
 Bytes
 ObjectDBFile::next()
 {
-  ReadLock(m_filelock);
-  // We are been lazy here; just use file lock as mutex
-  // for the access to the cache too
-  if (m_dummyCache.find(m_index) != map::end)
+  // Scoped shared lock for cache
   {
-    int index = m_index;
-    m_index++;
-    return m_dummyCache[index];
+    SLock(m_cacheLock);
+    // no need to read file if found in cache
+    if (m_dummyCache.find(m_index) != map::end)
+    {
+      int index = m_index;
+      m_index++;
+      return m_dummyCache[index];
+    }
   }
 
+  ReadLock(m_filelock);
+
   // m_index not found in cache
   Bytes co;
   if (m_index >= m_size)
@@ -152,6 +156,7 @@
 void
 ObjectDBFile::fillDummyCache()
 {
+  ULock(m_cacheLock);
   m_dummyCache.clear();
   int stop = (m_index + CACHE_SIZE < m_size) ? m_index + CACHE_SIZE : m_size;
   // the m_index should not change