CursorWindow can not be created due to cursor [memory] leak

记录了Android系统上由于cursor泄露导致内存耗尽（error -12）导致的CursorWindow不能再创建的Issue。

[Symptom]

08-30 20:27:36.751 E/CursorWindow(  760): Could not allocate CursorWindow '/data/data/com.android.providers.media/databases/external.db' of size 2097152 due to error -12.
08-30 20:27:36.771 E/JavaBinder(  760): *** Uncaught remote exception!  (Exceptions are not yet supported across processes.)
08-30 20:27:36.771 E/JavaBinder(  760): android.database.CursorWindowAllocationException: Cursor window allocation of 2048 kb failed. # Open Cursors=781 (# cursors opened by pid 3105=781)
08-30 20:27:36.771 E/JavaBinder(  760):  at android.database.CursorWindow.<init>(CursorWindow.java:104)
08-30 20:27:36.771 E/JavaBinder(  760):  at android.database.AbstractWindowedCursor.clearOrCreateWindow(AbstractWindowedCursor.java:198)
08-30 20:27:36.771 E/JavaBinder(  760):  at android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:162)
08-30 20:27:36.771 E/JavaBinder(  760):  at android.database.sqlite.SQLiteCursor.getCount(SQLiteCursor.java:156)
08-30 20:27:36.771 E/JavaBinder(  760):  at android.database.CursorToBulkCursorAdaptor.count(CursorToBulkCursorAdaptor.java:184)
08-30 20:27:36.771 E/JavaBinder(  760):  at android.content.ContentProviderNative.onTransact(ContentProviderNative.java:117)
08-30 20:27:36.771 E/JavaBinder(  760):  at android.os.Binder.execTransact(Binder.java:338)
08-30 20:27:36.771 E/JavaBinder(  760):  at dalvik.system.NativeStart.run(Native Method)

[Analysis]

logcat中有很明显的下列输出

Could not allocate CursorWindow '/data/data/com.android.providers.media/databases/external.db' of size 2097152due to error -12，

主要是due to error -12, ENOMEM，除非是其它原因内存耗尽，否则一般情况下是cursor泄露；注意errno是-12，如果是-24，EMFILE，则表示是进程内文件描述符耗尽，则未必是cursor泄露的原因。

继续从logcat中向前找，会发现大量的下列输出，

08-30 20:27:24.909 D/dalvikvm( 3105): GC_EXPLICIT freed 1686K, 26% free 15810K/21315K, paused 8ms+16ms
08-30 20:27:24.919 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:24.929 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:24.949 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:24.949 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:24.969 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:24.989 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:24.989 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:24.989 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:24.999 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:24.999 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:24.999 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.009 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.009 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.009 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.019 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.019 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.019 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.019 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.029 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.029 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.029 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.039 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.039 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.039 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.039 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.049 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.049 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.049 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.049 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.049 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.049 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.059 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.059 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.059 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.059 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.059 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.059 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.069 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.069 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.069 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.069 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.069 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.069 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.069 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.079 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.079 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.079 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.079 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.079 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:27:25.079 W/CursorWrapperInner( 3105): Cursor finalized without prior close()

08-30 20:26:57.179 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.189 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.209 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.229 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.249 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.259 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.269 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.279 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.299 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.299 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.299 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.309 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.309 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.309 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.309 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.309 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.319 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.319 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.319 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.319 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.319 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.329 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.339 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.339 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.339 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.349 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.349 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.349 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.359 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.359 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.369 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.369 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.369 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.369 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.369 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.379 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.379 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.389 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.389 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.389 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.389 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.399 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.399 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.399 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.399 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.409 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.409 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.409 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.409 W/CursorWrapperInner( 3105): Cursor finalized without prior close()
08-30 20:26:57.419 W/CursorWrapperInner( 3105): Cursor finalized without prior close()

说明有很明显的cursor leak。

解决办法是找到使用cursor的地方，在使用完毕后cursor.close()即可。

Cursor和CursorWindow的关系，参见Concepts of Cursor and CursorWindow on android platform