commit 90f43dce840b2a815426b6bfcdbe5f92358ab956
author Jamie Gennis <jgennis@google.com> Sun Oct 30 18:10:41 2011 -0700
committer Alex Ray <aray@google.com> Tue Jul 30 13:56:58 2013 -0700
tree 7c2ce777441fce483f62885c32c6b46181727a24
parent b37fbe9f810545bf62468fea5958325caa3635be

BlobCache: remove the mutex locking

This change removes the mutex from the BlobCache class.  The caller must
be responsible for thread synchronization in order to properly implement
the Flattenable interface, which is coming soon.  Otherwise would be the
potential for the cache contents to change between the call to the
getFlattenedSize and flatten methods.  Because the caller must do this
synchronization anyway there's no reason to also some synchronization
inside BlobCache.

Change-Id: Ie1f4f6f82b78744f46a41ce863cac0cad276a20e

include/utils/BlobCache.h

diff --git a/include/utils/BlobCache.h b/include/utils/BlobCache.h
index dc45ff0..11d4246 100644
--- a/include/utils/BlobCache.h
+++ b/include/utils/BlobCache.h
@@ -25,8 +25,8 @@
 
 namespace android {
 
-// A BlobCache is an in-memory cache for binary key/value pairs. All the public
-// methods are thread-safe.
+// A BlobCache is an in-memory cache for binary key/value pairs.  A BlobCache
+// does NOT provide any thread-safety guarantees.
 //
 // The cache contents can be serialized to a file and reloaded in a subsequent
 // execution of the program. This serialization is non-portable and should only
@@ -166,17 +166,12 @@
     size_t mTotalSize;
 
     // mRandState is the pseudo-random number generator state. It is passed to
-    // nrand48 to generate random numbers when needed. It must be protected by
-    // mMutex.
+    // nrand48 to generate random numbers when needed.
     unsigned short mRandState[3];
 
     // mCacheEntries stores all the cache entries that are resident in memory.
     // Cache entries are added to it by the 'set' method.
     SortedVector<CacheEntry> mCacheEntries;
-
-    // mMutex is used to synchronize access to all member variables.  It must be
-    // locked any time the member variables are written or read.
-    Mutex mMutex;
 };
 
 }

libs/utils/BlobCache.cpp

diff --git a/libs/utils/BlobCache.cpp b/libs/utils/BlobCache.cpp
index 4039807..24fdca8 100644
--- a/libs/utils/BlobCache.cpp
+++ b/libs/utils/BlobCache.cpp
@@ -67,7 +67,6 @@
         return;
     }
 
-    Mutex::Autolock lock(mMutex);
     sp<Blob> dummyKey(new Blob(key, keySize, false));
     CacheEntry dummyEntry(dummyKey, NULL);
 
@@ -129,7 +128,6 @@
                 keySize, mMaxKeySize);
         return 0;
     }
-    Mutex::Autolock lock(mMutex);
     sp<Blob> dummyKey(new Blob(key, keySize, false));
     CacheEntry dummyEntry(dummyKey, NULL);
     ssize_t index = mCacheEntries.indexOf(dummyEntry);