Make file objects as thread safe as the underlying libc FILE* implementation.

close() will now raise an IOError if any operations on the file object
are currently in progress in other threads.

Most code was written by Antoine Pitrou (pitrou).  Additional testing,
documentation and test suite cleanup done by me (gregory.p.smith).

Fixes issue 815646 and 595601 (as well as many other bugs and
references to this problem dating back to the dawn of Python).

Doc/c-api/file.rst

@@ -58,10 +58,42 @@ change in future releases of Python.
    closed.  Return *NULL* on failure.
 
 
-.. cfunction:: FILE* PyFile_AsFile(PyObject *p)
+.. cfunction:: FILE* PyFile_AsFile(PyObject \*p)
 
    Return the file object associated with *p* as a :ctype:`FILE\*`.
 
+   If the caller will ever use the returned :ctype:`FILE\*` object while
+   the GIL is released it must also call the `PyFile_IncUseCount` and
+   `PyFile_DecUseCount` functions described below as appropriate.
+
+
+.. cfunction:: void PyFile_IncUseCount(PyFileObject \*p)
+
+   Increments the PyFileObject's internal use count to indicate
+   that the underlying :ctype:`FILE\*` is being used.
+   This prevents Python from calling f_close() on it from another thread.
+   Callers of this must call `PyFile_DecUseCount` when they are
+   finished with the :ctype:`FILE\*`.  Otherwise the file object will
+   never be closed by Python.
+
+   The GIL must be held while calling this function.
+
+   The suggested use is to call this after `PyFile_AsFile` just before
+   you release the GIL.
+
+   .. versionadded:: 2.6
+
+
+.. cfunction:: void PyFile_DecUseCount(PyFileObject \*p)
+
+   Decrements the PyFileObject's internal unlocked_count member to
+   indicate that the caller is done with its own use of the :ctype:`FILE\*`.
+   This may only be called to undo a prior call to `PyFile_IncUseCount`.
+
+   The GIL must be held while calling this function.
+
+   .. versionadded:: 2.6
+
 
 .. cfunction:: PyObject* PyFile_GetLine(PyObject *p, int n)
 

Include/fileobject.h

@@ -25,6 +25,8 @@ typedef struct {
 	int f_skipnextlf;	/* Skip next \n */
 	PyObject *f_encoding;
 	PyObject *weakreflist; /* List of weak references */
+	int unlocked_count;	/* Num. currently running sections of code
+				   using f_fp with the GIL released. */
 } PyFileObject;
 
 PyAPI_DATA(PyTypeObject) PyFile_Type;
@@ -38,6 +40,8 @@ PyAPI_FUNC(int) PyFile_SetEncoding(PyObject *, const char *);
 PyAPI_FUNC(PyObject *) PyFile_FromFile(FILE *, char *, char *,
                                              int (*)(FILE *));
 PyAPI_FUNC(FILE *) PyFile_AsFile(PyObject *);
+PyAPI_FUNC(void) PyFile_IncUseCount(PyFileObject *);
+PyAPI_FUNC(void) PyFile_DecUseCount(PyFileObject *);
 PyAPI_FUNC(PyObject *) PyFile_Name(PyObject *);
 PyAPI_FUNC(PyObject *) PyFile_GetLine(PyObject *, int);
 PyAPI_FUNC(int) PyFile_WriteObject(PyObject *, PyObject *, int);

Lib/test/test_file.py

@@ -1,9 +1,13 @@
 import sys
 import os
 import unittest
+import itertools
+import time
+import threading
 from array import array
 from weakref import proxy
 
+from test import test_support
 from test.test_support import TESTFN, findfile, run_unittest
 from UserList import UserList
 
@@ -339,11 +343,173 @@ class FileSubclassTests(unittest.TestCase):
         self.failUnless(f.subclass_closed)
 
 
+class FileThreadingTests(unittest.TestCase):
+    # These tests check the ability to call various methods of file objects
+    # (including close()) concurrently without crashing the Python interpreter.
+    # See #815646, #595601
+
+    def setUp(self):
+        self.f = None
+        self.filename = TESTFN
+        with open(self.filename, "w") as f:
+            f.write("\n".join("0123456789"))
+        self._count_lock = threading.Lock()
+        self.close_count = 0
+        self.close_success_count = 0
+
+    def tearDown(self):
+        if self.f:
+            try:
+                self.f.close()
+            except (EnvironmentError, ValueError):
+                pass
+        try:
+            os.remove(self.filename)
+        except EnvironmentError:
+            pass
+
+    def _create_file(self):
+        self.f = open(self.filename, "w+")
+
+    def _close_file(self):
+        with self._count_lock:
+            self.close_count += 1
+        self.f.close()
+        with self._count_lock:
+            self.close_success_count += 1
+
+    def _close_and_reopen_file(self):
+        self._close_file()
+        # if close raises an exception thats fine, self.f remains valid so
+        # we don't need to reopen.
+        self._create_file()
+
+    def _run_workers(self, func, nb_workers, duration=0.2):
+        with self._count_lock:
+            self.close_count = 0
+            self.close_success_count = 0
+        self.do_continue = True
+        threads = []
+        try:
+            for i in range(nb_workers):
+                t = threading.Thread(target=func)
+                t.start()
+                threads.append(t)
+            for _ in xrange(100):
+                time.sleep(duration/100)
+                with self._count_lock:
+                    if self.close_count-self.close_success_count > nb_workers+1:
+                        if test_support.verbose:
+                            print 'Q',
+                        break
+            time.sleep(duration)
+        finally:
+            self.do_continue = False
+            for t in threads:
+                t.join()
+
+    def _test_close_open_io(self, io_func, nb_workers=5):
+        def worker():
+            self._create_file()
+            funcs = itertools.cycle((
+                lambda: io_func(),
+                lambda: self._close_and_reopen_file(),
+            ))
+            for f in funcs:
+                if not self.do_continue:
+                    break
+                try:
+                    f()
+                except (IOError, ValueError):
+                    pass
+        self._run_workers(worker, nb_workers)
+        if test_support.verbose:
+            # Useful verbose statistics when tuning this test to take
+            # less time to run but still ensuring that its still useful.
+            #
+            # the percent of close calls that raised an error
+            percent = 100. - 100.*self.close_success_count/self.close_count
+            print self.close_count, ('%.4f ' % percent),
+
+    def test_close_open(self):
+        def io_func():
+            pass
+        self._test_close_open_io(io_func)
+
+    def test_close_open_flush(self):
+        def io_func():
+            self.f.flush()
+        self._test_close_open_io(io_func)
+
+    def test_close_open_iter(self):
+        def io_func():
+            list(iter(self.f))
+        self._test_close_open_io(io_func)
+
+    def test_close_open_isatty(self):
+        def io_func():
+            self.f.isatty()
+        self._test_close_open_io(io_func)
+
+    def test_close_open_print(self):
+        def io_func():
+            print >> self.f, ''
+        self._test_close_open_io(io_func)
+
+    def test_close_open_read(self):
+        def io_func():
+            self.f.read(0)
+        self._test_close_open_io(io_func)
+
+    def test_close_open_readinto(self):
+        def io_func():
+            a = array('c', 'xxxxx')
+            self.f.readinto(a)
+        self._test_close_open_io(io_func)
+
+    def test_close_open_readline(self):
+        def io_func():
+            self.f.readline()
+        self._test_close_open_io(io_func)
+
+    def test_close_open_readlines(self):
+        def io_func():
+            self.f.readlines()
+        self._test_close_open_io(io_func)
+
+    def test_close_open_seek(self):
+        def io_func():
+            self.f.seek(0, 0)
+        self._test_close_open_io(io_func)
+
+    def test_close_open_tell(self):
+        def io_func():
+            self.f.tell()
+        self._test_close_open_io(io_func)
+
+    def test_close_open_truncate(self):
+        def io_func():
+            self.f.truncate()
+        self._test_close_open_io(io_func)
+
+    def test_close_open_write(self):
+        def io_func():
+            self.f.write('')
+        self._test_close_open_io(io_func)
+
+    def test_close_open_writelines(self):
+        def io_func():
+            self.f.writelines('')
+        self._test_close_open_io(io_func)
+
+
+
 def test_main():
     # Historically, these tests have been sloppy about removing TESTFN.
     # So get rid of it no matter what.
     try:
-        run_unittest(AutoFileTests, OtherFileTests, FileSubclassTests)
+        run_unittest(AutoFileTests, OtherFileTests, FileSubclassTests,
+            FileThreadingTests)
     finally:
         if os.path.exists(TESTFN):
             os.unlink(TESTFN)

Misc/NEWS

@@ -18,6 +18,11 @@ Extensions Modules
 Library
 -------
 
+- Issue #815646: Individual file objects may now be used from multiple
+  threads at once without fear of crashing the Python interpreter.  If
+  file.close() is called while an object is in use by another thread
+  an IOError exception will be raised and the file will not be closed.
+
 - The bundled libffi copy is now in sync with the recently released
   libffi3.0.5 version, apart from some small changes to
   Modules/_ctypes/libffi/configure.ac.

Objects/fileobject.c

@@ -48,6 +48,30 @@
 #define NEWLINE_LF 2		/* \n newline seen */
 #define NEWLINE_CRLF 4		/* \r\n newline seen */
 
+/*
+ * These macros release the GIL while preventing the f_close() function being
+ * called in the interval between them.  For that purpose, a running total of
+ * the number of currently running unlocked code sections is kept in
+ * the unlocked_count field of the PyFileObject. The close() method raises
+ * an IOError if that field is non-zero.  See issue #815646, #595601.
+ */
+
+#define FILE_BEGIN_ALLOW_THREADS(fobj) \
+{ \
+	fobj->unlocked_count++; \
+	Py_BEGIN_ALLOW_THREADS
+
+#define FILE_END_ALLOW_THREADS(fobj) \
+	Py_END_ALLOW_THREADS \
+	fobj->unlocked_count--; \
+	assert(fobj->unlocked_count >= 0); \
+}
+
+#define FILE_ABORT_ALLOW_THREADS(fobj) \
+	Py_BLOCK_THREADS \
+	fobj->unlocked_count--; \
+	assert(fobj->unlocked_count >= 0);
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -61,6 +85,17 @@ PyFile_AsFile(PyObject *f)
 		return ((PyFileObject *)f)->f_fp;
 }
 
+void PyFile_IncUseCount(PyFileObject *fobj)
+{
+	fobj->unlocked_count++;
+}
+
+void PyFile_DecUseCount(PyFileObject *fobj)
+{
+	fobj->unlocked_count--;
+	assert(fobj->unlocked_count >= 0);
+}
+
 PyObject *
 PyFile_Name(PyObject *f)
 {
@@ -70,6 +105,19 @@ PyFile_Name(PyObject *f)
 		return ((PyFileObject *)f)->f_name;
 }
 
+/* This is a safe wrapper around PyObject_Print to print to the FILE
+   of a PyFileObject. PyObject_Print releases the GIL but knows nothing
+   about PyFileObject. */
+static int
+file_PyObject_Print(PyObject *op, PyFileObject *f, int flags)
+{
+	int result;
+	PyFile_IncUseCount(f);
+	result = PyObject_Print(op, f->f_fp, flags);
+	PyFile_DecUseCount(f);
+	return result;
+}
+
 /* On Unix, fopen will succeed for directories.
    In Python, there should be no file objects referring to
    directories, so we need a check.  */
@@ -220,20 +268,20 @@ open_the_file(PyFileObject *f, char *name, char *mode)
 		PyObject *wmode;
 		wmode = PyUnicode_DecodeASCII(newmode, strlen(newmode), NULL);
 		if (f->f_name && wmode) {
-			Py_BEGIN_ALLOW_THREADS
+			FILE_BEGIN_ALLOW_THREADS(f)
 			/* PyUnicode_AS_UNICODE OK without thread
 			   lock as it is a simple dereference. */
 			f->f_fp = _wfopen(PyUnicode_AS_UNICODE(f->f_name),
 					  PyUnicode_AS_UNICODE(wmode));
-			Py_END_ALLOW_THREADS
+			FILE_END_ALLOW_THREADS(f)
 		}
 		Py_XDECREF(wmode);
 	}
 #endif
 	if (NULL == f->f_fp && NULL != name) {
-		Py_BEGIN_ALLOW_THREADS
+		FILE_BEGIN_ALLOW_THREADS(f)
 		f->f_fp = fopen(name, newmode);
-		Py_END_ALLOW_THREADS
+		FILE_END_ALLOW_THREADS(f)
 	}
 
 	if (f->f_fp == NULL) {
@@ -271,6 +319,48 @@ cleanup:
 	return (PyObject *)f;
 }
 
+static PyObject *
+close_the_file(PyFileObject *f)
+{
+	int sts = 0;
+	int (*local_close)(FILE *);
+	FILE *local_fp = f->f_fp;
+	if (local_fp != NULL) {
+		local_close = f->f_close;
+		if (local_close != NULL && f->unlocked_count > 0) {
+			if (f->ob_refcnt > 0) {
+				PyErr_SetString(PyExc_IOError,
+					"close() called during concurrent "
+					"operation on the same file object.");
+			} else {
+				/* This should not happen unless someone is
+				 * carelessly playing with the PyFileObject
+				 * struct fields and/or its associated FILE
+				 * pointer. */
+				PyErr_SetString(PyExc_SystemError,
+					"PyFileObject locking error in "
+					"destructor (refcnt <= 0 at close).");
+			}
+			return NULL;
+		}
+		/* NULL out the FILE pointer before releasing the GIL, because
+		 * it will not be valid anymore after the close() function is
+		 * called. */
+		f->f_fp = NULL;
+		if (local_close != NULL) {
+			Py_BEGIN_ALLOW_THREADS
+			errno = 0;
+			sts = (*local_close)(local_fp);
+			Py_END_ALLOW_THREADS
+			if (sts == EOF)
+				return PyErr_SetFromErrno(PyExc_IOError);
+			if (sts != 0)
+				return PyInt_FromLong((long)sts);
+		}
+	}
+	Py_RETURN_NONE;
+}
+
 PyObject *
 PyFile_FromFile(FILE *fp, char *name, char *mode, int (*close)(FILE *))
 {
@@ -386,15 +476,16 @@ static void drop_readahead(PyFileObject *);
 static void
 file_dealloc(PyFileObject *f)
 {
-	int sts = 0;
+	PyObject *ret;
 	if (f->weakreflist != NULL)
 		PyObject_ClearWeakRefs((PyObject *) f);
-	if (f->f_fp != NULL && f->f_close != NULL) {
-		Py_BEGIN_ALLOW_THREADS
-		sts = (*f->f_close)(f->f_fp);
-		Py_END_ALLOW_THREADS
-		if (sts == EOF) 
-			PySys_WriteStderr("close failed: [Errno %d] %s\n", errno, strerror(errno)); 
+	ret = close_the_file(f);
+	if (!ret) {
+		PySys_WriteStderr("close failed in file object destructor:\n");
+		PyErr_Print();
+	}
+	else {
+		Py_DECREF(ret);
 	}
 	PyMem_Free(f->f_setbuf);
 	Py_XDECREF(f->f_name);
@@ -432,24 +523,10 @@ file_repr(PyFileObject *f)
 static PyObject *
 file_close(PyFileObject *f)
 {
-	int sts = 0;
-	if (f->f_fp != NULL) {
-		if (f->f_close != NULL) {
-			Py_BEGIN_ALLOW_THREADS
-			errno = 0;
-			sts = (*f->f_close)(f->f_fp);
-			Py_END_ALLOW_THREADS
-		}
-		f->f_fp = NULL;
-	}
+	PyObject *sts = close_the_file(f);
 	PyMem_Free(f->f_setbuf);
 	f->f_setbuf = NULL;
-	if (sts == EOF)
-		return PyErr_SetFromErrno(PyExc_IOError);
-	if (sts != 0)
-		return PyInt_FromLong((long)sts);
-	Py_INCREF(Py_None);
-	return Py_None;
+	return sts;
 }
 
 
@@ -566,10 +643,10 @@ file_seek(PyFileObject *f, PyObject *args)
 	if (PyErr_Occurred())
 		return NULL;
 
-	Py_BEGIN_ALLOW_THREADS
+ 	FILE_BEGIN_ALLOW_THREADS(f)
 	errno = 0;
 	ret = _portable_fseek(f->f_fp, offset, whence);
-	Py_END_ALLOW_THREADS
+	FILE_END_ALLOW_THREADS(f)
 
 	if (ret != 0) {
 		PyErr_SetFromErrno(PyExc_IOError);
@@ -603,10 +680,10 @@ file_truncate(PyFileObject *f, PyObject *args)
 	 * then at least on Windows).  The easiest thing is to capture
 	 * current pos now and seek back to it at the end.
 	 */
-	Py_BEGIN_ALLOW_THREADS
+	FILE_BEGIN_ALLOW_THREADS(f)
 	errno = 0;
 	initialpos = _portable_ftell(f->f_fp);
-	Py_END_ALLOW_THREADS
+	FILE_END_ALLOW_THREADS(f)
 	if (initialpos == -1)
 		goto onioerror;
 
@@ -631,10 +708,10 @@ file_truncate(PyFileObject *f, PyObject *args)
 	 * I/O, and a flush may be necessary to synch both platform views
 	 * of the current file state.
 	 */
-	Py_BEGIN_ALLOW_THREADS
+	FILE_BEGIN_ALLOW_THREADS(f)
 	errno = 0;
 	ret = fflush(f->f_fp);
-	Py_END_ALLOW_THREADS
+	FILE_END_ALLOW_THREADS(f)
 	if (ret != 0)
 		goto onioerror;
 
@@ -645,15 +722,15 @@ file_truncate(PyFileObject *f, PyObject *args)
 		HANDLE hFile;
 
 		/* Have to move current pos to desired endpoint on Windows. */
-		Py_BEGIN_ALLOW_THREADS
+		FILE_BEGIN_ALLOW_THREADS(f)
 		errno = 0;
 		ret = _portable_fseek(f->f_fp, newsize, SEEK_SET) != 0;
-		Py_END_ALLOW_THREADS
+		FILE_END_ALLOW_THREADS(f)
 		if (ret)
 			goto onioerror;
 
 		/* Truncate.  Note that this may grow the file! */
-		Py_BEGIN_ALLOW_THREADS
+		FILE_BEGIN_ALLOW_THREADS(f)
 		errno = 0;
 		hFile = (HANDLE)_get_osfhandle(fileno(f->f_fp));
 		ret = hFile == (HANDLE)-1;
@@ -662,24 +739,24 @@ file_truncate(PyFileObject *f, PyObject *args)
 			if (ret)
 				errno = EACCES;
 		}
-		Py_END_ALLOW_THREADS
+		FILE_END_ALLOW_THREADS(f)
 		if (ret)
 			goto onioerror;
 	}
 #else
-	Py_BEGIN_ALLOW_THREADS
+	FILE_BEGIN_ALLOW_THREADS(f)
 	errno = 0;
 	ret = ftruncate(fileno(f->f_fp), newsize);
-	Py_END_ALLOW_THREADS
+	FILE_END_ALLOW_THREADS(f)
 	if (ret != 0)
 		goto onioerror;
 #endif /* !MS_WINDOWS */
 
 	/* Restore original file position. */
-	Py_BEGIN_ALLOW_THREADS
+	FILE_BEGIN_ALLOW_THREADS(f)
 	errno = 0;
 	ret = _portable_fseek(f->f_fp, initialpos, SEEK_SET) != 0;
-	Py_END_ALLOW_THREADS
+	FILE_END_ALLOW_THREADS(f)
 	if (ret)
 		goto onioerror;
 
@@ -700,10 +777,11 @@ file_tell(PyFileObject *f)
 
 	if (f->f_fp == NULL)
 		return err_closed();
-	Py_BEGIN_ALLOW_THREADS
+	FILE_BEGIN_ALLOW_THREADS(f)
 	errno = 0;
 	pos = _portable_ftell(f->f_fp);
-	Py_END_ALLOW_THREADS
+	FILE_END_ALLOW_THREADS(f)
+
 	if (pos == -1) {
 		PyErr_SetFromErrno(PyExc_IOError);
 		clearerr(f->f_fp);
@@ -740,10 +818,10 @@ file_flush(PyFileObject *f)
 
 	if (f->f_fp == NULL)
 		return err_closed();
-	Py_BEGIN_ALLOW_THREADS
+	FILE_BEGIN_ALLOW_THREADS(f)
 	errno = 0;
 	res = fflush(f->f_fp);
-	Py_END_ALLOW_THREADS
+	FILE_END_ALLOW_THREADS(f)
 	if (res != 0) {
 		PyErr_SetFromErrno(PyExc_IOError);
 		clearerr(f->f_fp);
@@ -759,9 +837,9 @@ file_isatty(PyFileObject *f)
 	long res;
 	if (f->f_fp == NULL)
 		return err_closed();
-	Py_BEGIN_ALLOW_THREADS
+	FILE_BEGIN_ALLOW_THREADS(f)
 	res = isatty((int)fileno(f->f_fp));
-	Py_END_ALLOW_THREADS
+	FILE_END_ALLOW_THREADS(f)
 	return PyBool_FromLong(res);
 }
 
@@ -861,11 +939,11 @@ file_read(PyFileObject *f, PyObject *args)
 		return NULL;
 	bytesread = 0;
 	for (;;) {
-		Py_BEGIN_ALLOW_THREADS
+		FILE_BEGIN_ALLOW_THREADS(f)
 		errno = 0;
 		chunksize = Py_UniversalNewlineFread(BUF(v) + bytesread,
 			  buffersize - bytesread, f->f_fp, (PyObject *)f);
-		Py_END_ALLOW_THREADS
+		FILE_END_ALLOW_THREADS(f)
 		if (chunksize == 0) {
 			if (!ferror(f->f_fp))
 				break;
@@ -917,11 +995,11 @@ file_readinto(PyFileObject *f, PyObject *args)
 		return NULL;
 	ndone = 0;
 	while (ntodo > 0) {
-		Py_BEGIN_ALLOW_THREADS
+		FILE_BEGIN_ALLOW_THREADS(f)
 		errno = 0;
 		nnow = Py_UniversalNewlineFread(ptr+ndone, ntodo, f->f_fp,
 						(PyObject *)f);
-		Py_END_ALLOW_THREADS
+		FILE_END_ALLOW_THREADS(f)
 		if (nnow == 0) {
 			if (!ferror(f->f_fp))
 				break;
@@ -986,7 +1064,7 @@ trailing null byte.  #define DONT_USE_FGETS_IN_GETLINE to disable this code.
 
 #ifdef USE_FGETS_IN_GETLINE
 static PyObject*
-getline_via_fgets(FILE *fp)
+getline_via_fgets(PyFileObject *f, FILE *fp)
 {
 /* INITBUFSIZE is the maximum line length that lets us get away with the fast
  * no-realloc, one-fgets()-call path.  Boosting it isn't free, because we have
@@ -1019,13 +1097,13 @@ getline_via_fgets(FILE *fp)
 	total_v_size = INITBUFSIZE;	/* start small and pray */
 	pvfree = buf;
 	for (;;) {
-		Py_BEGIN_ALLOW_THREADS
+		FILE_BEGIN_ALLOW_THREADS(f)
 		pvend = buf + total_v_size;
 		nfree = pvend - pvfree;
 		memset(pvfree, '\n', nfree);
 		assert(nfree < INT_MAX); /* Should be atmost MAXBUFSIZE */
 		p = fgets(pvfree, (int)nfree, fp);
-		Py_END_ALLOW_THREADS
+		FILE_END_ALLOW_THREADS(f)
 
 		if (p == NULL) {
 			clearerr(fp);
@@ -1094,13 +1172,13 @@ getline_via_fgets(FILE *fp)
 	 * the code above for detailed comments about the logic.
 	 */
 	for (;;) {
-		Py_BEGIN_ALLOW_THREADS
+		FILE_BEGIN_ALLOW_THREADS(f)
 		pvend = BUF(v) + total_v_size;
 		nfree = pvend - pvfree;
 		memset(pvfree, '\n', nfree);
 		assert(nfree < INT_MAX);
 		p = fgets(pvfree, (int)nfree, fp);
-		Py_END_ALLOW_THREADS
+		FILE_END_ALLOW_THREADS(f)
 
 		if (p == NULL) {
 			clearerr(fp);
@@ -1171,7 +1249,7 @@ get_line(PyFileObject *f, int n)
 
 #if defined(USE_FGETS_IN_GETLINE)
 	if (n <= 0 && !univ_newline )
-		return getline_via_fgets(fp);
+		return getline_via_fgets(f, fp);
 #endif
 	total_v_size = n > 0 ? n : 100;
 	v = PyString_FromStringAndSize((char *)NULL, total_v_size);
@@ -1181,7 +1259,7 @@ get_line(PyFileObject *f, int n)
 	end = buf + total_v_size;
 
 	for (;;) {
-		Py_BEGIN_ALLOW_THREADS
+		FILE_BEGIN_ALLOW_THREADS(f)
 		FLOCKFILE(fp);
 		if (univ_newline) {
 			c = 'x'; /* Shut up gcc warning */
@@ -1216,7 +1294,7 @@ get_line(PyFileObject *f, int n)
 			buf != end)
 			;
 		FUNLOCKFILE(fp);
-		Py_END_ALLOW_THREADS
+		FILE_END_ALLOW_THREADS(f)
 		f->f_newlinetypes = newlinetypes;
 		f->f_skipnextlf = skipnextlf;
 		if (c == '\n')
@@ -1381,7 +1459,7 @@ static PyObject *
 file_readlines(PyFileObject *f, PyObject *args)
 {
 	long sizehint = 0;
-	PyObject *list;
+	PyObject *list = NULL;
 	PyObject *line;
 	char small_buffer[SMALLCHUNK];
 	char *buffer = small_buffer;
@@ -1409,11 +1487,11 @@ file_readlines(PyFileObject *f, PyObject *args)
 		if (shortread)
 			nread = 0;
 		else {
-			Py_BEGIN_ALLOW_THREADS
+			FILE_BEGIN_ALLOW_THREADS(f)
 			errno = 0;
 			nread = Py_UniversalNewlineFread(buffer+nfilled,
 				buffersize-nfilled, f->f_fp, (PyObject *)f);
-			Py_END_ALLOW_THREADS
+			FILE_END_ALLOW_THREADS(f)
 			shortread = (nread < buffersize-nfilled);
 		}
 		if (nread == 0) {
@@ -1422,10 +1500,7 @@ file_readlines(PyFileObject *f, PyObject *args)
 				break;
 			PyErr_SetFromErrno(PyExc_IOError);
 			clearerr(f->f_fp);
-		  error:
-			Py_DECREF(list);
-			list = NULL;
-			goto cleanup;
+			goto error;
 		}
 		totalread += nread;
 		p = (char *)memchr(buffer+nfilled, '\n', nread);
@@ -1499,9 +1574,14 @@ file_readlines(PyFileObject *f, PyObject *args)
 		if (err != 0)
 			goto error;
 	}
-  cleanup:
+
+cleanup:
 	Py_XDECREF(big_buffer);
 	return list;
+
+error:
+	Py_CLEAR(list);
+	goto cleanup;
 }
 
 static PyObject *
@@ -1514,10 +1594,10 @@ file_write(PyFileObject *f, PyObject *args)
 	if (!PyArg_ParseTuple(args, f->f_binary ? "s#" : "t#", &s, &n))
 		return NULL;
 	f->f_softspace = 0;
-	Py_BEGIN_ALLOW_THREADS
+	FILE_BEGIN_ALLOW_THREADS(f)
 	errno = 0;
 	n2 = fwrite(s, 1, n, f->f_fp);
-	Py_END_ALLOW_THREADS
+	FILE_END_ALLOW_THREADS(f)
 	if (n2 != n) {
 		PyErr_SetFromErrno(PyExc_IOError);
 		clearerr(f->f_fp);
@@ -1615,8 +1695,8 @@ file_writelines(PyFileObject *f, PyObject *seq)
 
 		/* Since we are releasing the global lock, the
 		   following code may *not* execute Python code. */
-		Py_BEGIN_ALLOW_THREADS
 		f->f_softspace = 0;
+		FILE_BEGIN_ALLOW_THREADS(f)
 		errno = 0;
 		for (i = 0; i < j; i++) {
 		    	line = PyList_GET_ITEM(list, i);
@@ -1624,13 +1704,13 @@ file_writelines(PyFileObject *f, PyObject *seq)
 			nwritten = fwrite(PyString_AS_STRING(line),
 					  1, len, f->f_fp);
 			if (nwritten != len) {
-				Py_BLOCK_THREADS
+				FILE_ABORT_ALLOW_THREADS(f)
 				PyErr_SetFromErrno(PyExc_IOError);
 				clearerr(f->f_fp);
 				goto error;
 			}
 		}
-		Py_END_ALLOW_THREADS
+		FILE_END_ALLOW_THREADS(f)
 
 		if (j < CHUNKSIZE)
 			break;
@@ -1895,11 +1975,11 @@ readahead(PyFileObject *f, int bufsize)
 		PyErr_NoMemory();
 		return -1;
 	}
-	Py_BEGIN_ALLOW_THREADS
+	FILE_BEGIN_ALLOW_THREADS(f)
 	errno = 0;
 	chunksize = Py_UniversalNewlineFread(
 		f->f_buf, bufsize, f->f_fp, (PyObject *)f);
-	Py_END_ALLOW_THREADS
+	FILE_END_ALLOW_THREADS(f)
 	if (chunksize == 0) {
 		if (ferror(f->f_fp)) {
 			PyErr_SetFromErrno(PyExc_IOError);
@@ -2008,6 +2088,7 @@ file_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 		Py_INCREF(Py_None);
 		((PyFileObject *)self)->f_encoding = Py_None;
 		((PyFileObject *)self)->weakreflist = NULL;
+		((PyFileObject *)self)->unlocked_count = 0;
 	}
 	return self;
 }
@@ -2195,12 +2276,12 @@ PyFile_WriteObject(PyObject *v, PyObject *f, int flags)
 		return -1;
 	}
 	else if (PyFile_Check(f)) {
-		FILE *fp = PyFile_AsFile(f);
+		PyFileObject *fobj = (PyFileObject *) f;
 #ifdef Py_USING_UNICODE
-		PyObject *enc = ((PyFileObject*)f)->f_encoding;
+		PyObject *enc = fobj->f_encoding;
 		int result;
 #endif
-		if (fp == NULL) {
+		if (fobj->f_fp == NULL) {
 			err_closed();
 			return -1;
 		}
@@ -2215,11 +2296,11 @@ PyFile_WriteObject(PyObject *v, PyObject *f, int flags)
 			value = v;
 			Py_INCREF(value);
 		}
-		result = PyObject_Print(value, fp, flags);
+		result = file_PyObject_Print(value, fobj, flags);
 		Py_DECREF(value);
 		return result;
 #else
-		return PyObject_Print(v, fp, flags);
+		return file_PyObject_Print(v, fobj, flags);
 #endif
 	}
 	writer = PyObject_GetAttrString(f, "write");
@@ -2257,6 +2338,7 @@ PyFile_WriteObject(PyObject *v, PyObject *f, int flags)
 int
 PyFile_WriteString(const char *s, PyObject *f)
 {
+
 	if (f == NULL) {
 		/* Should be caused by a pre-existing error */
 		if (!PyErr_Occurred())
@@ -2265,14 +2347,15 @@ PyFile_WriteString(const char *s, PyObject *f)
 		return -1;
 	}
 	else if (PyFile_Check(f)) {
+		PyFileObject *fobj = (PyFileObject *) f;
 		FILE *fp = PyFile_AsFile(f);
 		if (fp == NULL) {
 			err_closed();
 			return -1;
 		}
-		Py_BEGIN_ALLOW_THREADS
+		FILE_BEGIN_ALLOW_THREADS(fobj)
 		fputs(s, fp);
-		Py_END_ALLOW_THREADS
+		FILE_END_ALLOW_THREADS(fobj)
 		return 0;
 	}
 	else if (!PyErr_Occurred()) {