[Python-checkins] r74581 - in python/trunk: Lib/test/test_io.py Misc/NEWS Modules/_io/textio.c

Sat Aug 29 20:14:40 CEST 2009

Author: amaury.forgeotdarc
Date: Sat Aug 29 20:14:40 2009
New Revision: 74581
Log:
#6750: TextIOWrapped could duplicate output when several threads write to it.
this affect text files opened with io.open(), and the print() function of py3k
Modified:
 python/trunk/Lib/test/test_io.py
 python/trunk/Misc/NEWS
 python/trunk/Modules/_io/textio.c
Modified: python/trunk/Lib/test/test_io.py
==============================================================================

--- python/trunk/Lib/test/test_io.py	(original)
+++ python/trunk/Lib/test/test_io.py	Sat Aug 29 20:14:40 2009
@@ -2061,6 +2061,27 @@
 self.assertEqual(f.errors, "replace")
 
 
+ def test_threads_write(self):
+ # Issue6750: concurrent writes could duplicate data
+ event = threading.Event()
+ with self.open(support.TESTFN, "w", buffering=1) as f:
+ def run(n):
+ text = "Thread%03d\n" % n
+ event.wait()
+ f.write(text)
+ threads = [threading.Thread(target=lambda n=x: run(n))
+ for x in range(20)]
+ for t in threads:
+ t.start()
+ time.sleep(0.02)
+ event.set()
+ for t in threads:
+ t.join()
+ with self.open(support.TESTFN) as f:
+ content = f.read()
+ for n in range(20):
+ self.assertEquals(content.count("Thread%03d\n" % n), 1)
+
 class CTextIOWrapperTest(TextIOWrapperTest):
 
 def test_initialization(self):
Modified: python/trunk/Misc/NEWS
==============================================================================
--- python/trunk/Misc/NEWS	(original)
+++ python/trunk/Misc/NEWS	Sat Aug 29 20:14:40 2009
@@ -12,6 +12,9 @@
 Core and Builtins
 -----------------
 
+- Issue #6750: A text file opened with io.open() could duplicate its output
+ when writing from multiple threads at the same time.
+
 - Issue #6704: Improve the col_offset in AST for "for" statements with
 a target of tuple unpacking.
 
Modified: python/trunk/Modules/_io/textio.c
==============================================================================
--- python/trunk/Modules/_io/textio.c	(original)
+++ python/trunk/Modules/_io/textio.c	Sat Aug 29 20:14:40 2009
@@ -1189,11 +1189,18 @@
 static int
 _textiowrapper_writeflush(textio *self)
 {
- PyObject *b, *ret;
+ PyObject *pending, *b, *ret;
 
 if (self->pending_bytes == NULL)
 return 0;
- b = _PyBytes_Join(_PyIO_empty_bytes, self->pending_bytes);
+
+ pending = self->pending_bytes;
+ Py_INCREF(pending);
+ self->pending_bytes_count = 0;
+ Py_CLEAR(self->pending_bytes);
+
+ b = _PyBytes_Join(_PyIO_empty_bytes, pending);
+ Py_DECREF(pending);
 if (b == NULL)
 return -1;
 ret = PyObject_CallMethodObjArgs(self->buffer,
@@ -1202,8 +1209,6 @@
 if (ret == NULL)
 return -1;
 Py_DECREF(ret);
- Py_CLEAR(self->pending_bytes);
- self->pending_bytes_count = 0;
 return 0;
 }
 
