Breaking sleep after yield into small quanta.

Rationale: there is no reason to sleep for 4 seconds between
transactions if there is no one using the database.  This long
sleep only makes sense if two threads are actively using 
the database yielding to each other every several seconds.

1 files changed, 68 insertions, 55 deletions

diff --git a/core/java/android/database/sqlite/SQLiteDatabase.java b/core/java/android/database/sqlite/SQLiteDatabase.java
index 5d7af69..57bf3f7 100644
--- a/core/java/android/database/sqlite/SQLiteDatabase.java
+++ b/core/java/android/database/sqlite/SQLiteDatabase.java
@@ -62,53 +62,53 @@ public class SQLiteDatabase extends SQLiteClosable {
      */
     public enum ConflictAlgorithm {
         /**
-         *  When a constraint violation occurs, an immediate ROLLBACK occurs, 
-         * thus ending the current transaction, and the command aborts with a 
-         * return code of SQLITE_CONSTRAINT. If no transaction is active 
+         *  When a constraint violation occurs, an immediate ROLLBACK occurs,
+         * thus ending the current transaction, and the command aborts with a
+         * return code of SQLITE_CONSTRAINT. If no transaction is active
          * (other than the implied transaction that is created on every command)
          *  then this algorithm works the same as ABORT.
          */
         ROLLBACK("ROLLBACK"),
-        
+
         /**
-         * When a constraint violation occurs,no ROLLBACK is executed 
-         * so changes from prior commands within the same transaction 
+         * When a constraint violation occurs,no ROLLBACK is executed
+         * so changes from prior commands within the same transaction
          * are preserved. This is the default behavior.
          */
         ABORT("ABORT"),
-        
+
         /**
-         * When a constraint violation occurs, the command aborts with a return 
-         * code SQLITE_CONSTRAINT. But any changes to the database that 
-         * the command made prior to encountering the constraint violation 
+         * When a constraint violation occurs, the command aborts with a return
+         * code SQLITE_CONSTRAINT. But any changes to the database that
+         * the command made prior to encountering the constraint violation
          * are preserved and are not backed out.
          */
         FAIL("FAIL"),
-        
+
         /**
-         * When a constraint violation occurs, the one row that contains 
-         * the constraint violation is not inserted or changed. 
-         * But the command continues executing normally. Other rows before and 
-         * after the row that contained the constraint violation continue to be 
+         * When a constraint violation occurs, the one row that contains
+         * the constraint violation is not inserted or changed.
+         * But the command continues executing normally. Other rows before and
+         * after the row that contained the constraint violation continue to be
          * inserted or updated normally. No error is returned.
          */
         IGNORE("IGNORE"),
-        
+
         /**
          * When a UNIQUE constraint violation occurs, the pre-existing rows that
-         * are causing the constraint violation are removed prior to inserting 
+         * are causing the constraint violation are removed prior to inserting
          * or updating the current row. Thus the insert or update always occurs.
-         * The command continues executing normally. No error is returned. 
+         * The command continues executing normally. No error is returned.
          * If a NOT NULL constraint violation occurs, the NULL value is replaced
-         * by the default value for that column. If the column has no default 
-         * value, then the ABORT algorithm is used. If a CHECK constraint 
-         * violation occurs then the IGNORE algorithm is used. When this conflict 
-         * resolution strategy deletes rows in order to satisfy a constraint, 
+         * by the default value for that column. If the column has no default
+         * value, then the ABORT algorithm is used. If a CHECK constraint
+         * violation occurs then the IGNORE algorithm is used. When this conflict
+         * resolution strategy deletes rows in order to satisfy a constraint,
          * it does not invoke delete triggers on those rows.
          *  This behavior might change in a future release.
          */
         REPLACE("REPLACE");
-        
+
         private final String mValue;
         ConflictAlgorithm(String value) {
             mValue = value;
@@ -117,7 +117,7 @@ public class SQLiteDatabase extends SQLiteClosable {
             return mValue;
         }
     }
-    
+
     /**
      * Maximum Length Of A LIKE Or GLOB Pattern
      * The pattern matching algorithm used in the default LIKE and GLOB implementation
@@ -180,17 +180,19 @@ public class SQLiteDatabase extends SQLiteClosable {
 
     private long mLockAcquiredWallTime = 0L;
     private long mLockAcquiredThreadTime = 0L;
-    
+
     // limit the frequency of complaints about each database to one within 20 sec
-    // unless run command adb shell setprop log.tag.Database VERBOSE  
+    // unless run command adb shell setprop log.tag.Database VERBOSE
     private static final int LOCK_WARNING_WINDOW_IN_MS = 20000;
     /** If the lock is held this long then a warning will be printed when it is released. */
     private static final int LOCK_ACQUIRED_WARNING_TIME_IN_MS = 300;
     private static final int LOCK_ACQUIRED_WARNING_THREAD_TIME_IN_MS = 100;
     private static final int LOCK_ACQUIRED_WARNING_TIME_IN_MS_ALWAYS_PRINT = 2000;
 
+    private static final int SLEEP_AFTER_YIELD_QUANTUM = 500;
+
     private long mLastLockMessageTime = 0L;
-    
+
     /** Used by native code, do not rename */
     /* package */ int mNativeHandle = 0;
 
@@ -205,15 +207,15 @@ public class SQLiteDatabase extends SQLiteClosable {
 
     /** The optional factory to use when creating new Cursors */
     private CursorFactory mFactory;
-    
+
     private WeakHashMap<SQLiteClosable, Object> mPrograms;
- 
+
     private final RuntimeException mLeakedException;
 
     // package visible, since callers will access directly to minimize overhead in the case
     // that logging is not enabled.
     /* package */ final boolean mLogStats;
-    
+
     /**
      * @param closable
      */
@@ -225,7 +227,7 @@ public class SQLiteDatabase extends SQLiteClosable {
             unlock();
         }
     }
-    
+
     void removeSQLiteClosable(SQLiteClosable closable) {
         lock();
         try {
@@ -233,8 +235,8 @@ public class SQLiteDatabase extends SQLiteClosable {
         } finally {
             unlock();
         }
-    }    
-   
+    }
+
     @Override
     protected void onAllReferencesReleased() {
         if (isOpen()) {
@@ -245,10 +247,10 @@ public class SQLiteDatabase extends SQLiteClosable {
     /**
      * Attempts to release memory that SQLite holds but does not require to
      * operate properly. Typically this memory will come from the page cache.
-     * 
+     *
      * @return the number of bytes actually released
      */
-    static public native int releaseMemory(); 
+    static public native int releaseMemory();
 
     /**
      * Control whether or not the SQLiteDatabase is made thread-safe by using locks
@@ -284,7 +286,7 @@ public class SQLiteDatabase extends SQLiteClosable {
      * touch the native sqlite3* object since it is single threaded and uses
      * a polling lock contention algorithm. The lock is recursive, and may be acquired
      * multiple times by the same thread. This is a no-op if mLockingEnabled is false.
-     * 
+     *
      * @see #unlock()
      */
     /* package */ void lock() {
@@ -320,7 +322,7 @@ public class SQLiteDatabase extends SQLiteClosable {
 
     /**
      * Releases the database lock. This is a no-op if mLockingEnabled is false.
-     * 
+     *
      * @see #unlock()
      */
     /* package */ void unlock() {
@@ -350,7 +352,7 @@ public class SQLiteDatabase extends SQLiteClosable {
     private void checkLockHoldTime() {
         // Use elapsed real-time since the CPU may sleep when waiting for IO
         long elapsedTime = SystemClock.elapsedRealtime();
-        long lockedTime = elapsedTime - mLockAcquiredWallTime;                
+        long lockedTime = elapsedTime - mLockAcquiredWallTime;
         if (lockedTime < LOCK_ACQUIRED_WARNING_TIME_IN_MS_ALWAYS_PRINT &&
                 !Log.isLoggable(TAG, Log.VERBOSE) &&
                 (elapsedTime - mLastLockMessageTime) < LOCK_WARNING_WINDOW_IN_MS) {
@@ -567,10 +569,21 @@ public class SQLiteDatabase extends SQLiteClosable {
             }
         }
         if (sleepAfterYieldDelay > 0) {
-            try {
-                Thread.sleep(sleepAfterYieldDelay);
-            } catch (InterruptedException e) {
-                Thread.interrupted();
+            // Sleep for up to sleepAfterYieldDelay milliseconds, waking up periodically to
+            // check if anyone is using the database.  If the database is not contended,
+            // retake the lock and return.
+            long remainingDelay = sleepAfterYieldDelay;
+            while (remainingDelay > 0) {
+                try {
+                    Thread.sleep(remainingDelay < SLEEP_AFTER_YIELD_QUANTUM ?
+                            remainingDelay : SLEEP_AFTER_YIELD_QUANTUM);
+                } catch (InterruptedException e) {
+                    Thread.interrupted();
+                }
+                remainingDelay -= SLEEP_AFTER_YIELD_QUANTUM;
+                if (mLock.getQueueLength() == 0) {
+                    break;
+                }
             }
         }
         beginTransaction();
@@ -720,9 +733,9 @@ public class SQLiteDatabase extends SQLiteClosable {
             if (program != null) {
                 program.onAllReferencesReleasedFromContainer();
             }
-        }        
+        }
     }
-    
+
     /**
      * Native call to close the database.
      */
@@ -1157,8 +1170,8 @@ public class SQLiteDatabase extends SQLiteClosable {
 
     /**
      * Runs the provided SQL and returns a cursor over the result set.
-     * The cursor will read an initial set of rows and the return to the caller. 
-     * It will continue to read in batches and send data changed notifications 
+     * The cursor will read an initial set of rows and the return to the caller.
+     * It will continue to read in batches and send data changed notifications
      * when the later batches are ready.
      * @param sql the SQL query. The SQL string must not be ; terminated
      * @param selectionArgs You may include ?s in where clause in the query,
@@ -1167,19 +1180,19 @@ public class SQLiteDatabase extends SQLiteClosable {
      * @param initialRead set the initial count of items to read from the cursor
      * @param maxRead set the count of items to read on each iteration after the first
      * @return A {@link Cursor} object, which is positioned before the first entry
-     * 
+     *
      * This work is incomplete and not fully tested or reviewed, so currently
      * hidden.
      * @hide
      */
-    public Cursor rawQuery(String sql, String[] selectionArgs, 
+    public Cursor rawQuery(String sql, String[] selectionArgs,
             int initialRead, int maxRead) {
         SQLiteCursor c = (SQLiteCursor)rawQueryWithFactory(
                 null, sql, selectionArgs, null);
         c.setLoadStyle(initialRead, maxRead);
         return c;
     }
-    
+
     /**
      * Convenience method for inserting a row into the database.
      *
@@ -1232,7 +1245,7 @@ public class SQLiteDatabase extends SQLiteClosable {
      */
     public long replace(String table, String nullColumnHack, ContentValues initialValues) {
         try {
-            return insertWithOnConflict(table, nullColumnHack, initialValues, 
+            return insertWithOnConflict(table, nullColumnHack, initialValues,
                     ConflictAlgorithm.REPLACE);
         } catch (SQLException e) {
             Log.e(TAG, "Error inserting " + initialValues, e);
@@ -1254,7 +1267,7 @@ public class SQLiteDatabase extends SQLiteClosable {
      */
     public long replaceOrThrow(String table, String nullColumnHack,
             ContentValues initialValues) throws SQLException {
-        return insertWithOnConflict(table, nullColumnHack, initialValues, 
+        return insertWithOnConflict(table, nullColumnHack, initialValues,
                 ConflictAlgorithm.REPLACE);
     }
 
@@ -1410,7 +1423,7 @@ public class SQLiteDatabase extends SQLiteClosable {
     public int update(String table, ContentValues values, String whereClause, String[] whereArgs) {
         return updateWithOnConflict(table, values, whereClause, whereArgs, null);
     }
-    
+
     /**
      * Convenience method for updating rows in the database.
      *
@@ -1423,7 +1436,7 @@ public class SQLiteDatabase extends SQLiteClosable {
      * @return the number of rows affected
      * @hide
      */
-    public int updateWithOnConflict(String table, ContentValues values, 
+    public int updateWithOnConflict(String table, ContentValues values,
             String whereClause, String[] whereArgs, ConflictAlgorithm algorithm) {
         if (!isOpen()) {
             throw new IllegalStateException("database not open");
@@ -1440,7 +1453,7 @@ public class SQLiteDatabase extends SQLiteClosable {
             sql.append(algorithm.value());
             sql.append(" ");
         }
-        
+
         sql.append(table);
         sql.append(" SET ");
 
@@ -1601,7 +1614,7 @@ public class SQLiteDatabase extends SQLiteClosable {
         mFlags = flags;
         mPath = path;
         mLogStats = "1".equals(android.os.SystemProperties.get("db.logstats"));
-        
+
         mLeakedException = new IllegalStateException(path +
             " SQLiteDatabase created and never closed");
         mFactory = factory;