diff -r 02b8a061203a Lib/io.py
--- a/Lib/io.py	Thu Aug 14 17:56:07 2008 +0200
+++ b/Lib/io.py	Thu Aug 14 21:20:29 2008 +0200
@@ -63,6 +63,7 @@ import codecs
 import codecs
 import _fileio
 import warnings
+import threading
 
 # open() uses st_blksize whenever we can
 DEFAULT_BUFFER_SIZE = 8 * 1024 # bytes
@@ -1022,43 +1023,51 @@ class BufferedWriter(_BufferedIOMixin):
 if max_buffer_size is None
 else max_buffer_size)
 self._write_buf = bytearray()
+ self._write_lock = threading.Lock()
 
 def write(self, b):
 if self.closed:
 raise ValueError("write to closed file")
 if isinstance(b, unicode):
 raise TypeError("can't write unicode to binary stream")
- # XXX we can implement some more tricks to try and avoid partial writes
- if len(self._write_buf)> self.buffer_size:
- # We're full, so let's pre-flush the buffer
- try:
- self.flush()
- except BlockingIOError as e:
- # We can't accept anything else.
- # XXX Why not just let the exception pass through?
- raise BlockingIOError(e.errno, e.strerror, 0)
- before = len(self._write_buf)
- self._write_buf.extend(b)
- written = len(self._write_buf) - before
- if len(self._write_buf)> self.buffer_size:
- try:
- self.flush()
- except BlockingIOError as e:
- if (len(self._write_buf)> self.max_buffer_size):
- # We've hit max_buffer_size. We have to accept a partial
- # write and cut back our buffer.
- overage = len(self._write_buf) - self.max_buffer_size
- self._write_buf = self._write_buf[:self.max_buffer_size]
- raise BlockingIOError(e.errno, e.strerror, overage)
- return written
+ with self._write_lock:
+ # XXX we can implement some more tricks to try and avoid
+ # partial writes
+ if len(self._write_buf)> self.buffer_size:
+ # We're full, so let's pre-flush the buffer
+ try:
+ self._flush_unlocked()
+ except BlockingIOError as e:
+ # We can't accept anything else.
+ # XXX Why not just let the exception pass through?
+ raise BlockingIOError(e.errno, e.strerror, 0)
+ before = len(self._write_buf)
+ self._write_buf.extend(b)
+ written = len(self._write_buf) - before
+ if len(self._write_buf)> self.buffer_size:
+ try:
+ self._flush_unlocked()
+ except BlockingIOError as e:
+ if len(self._write_buf)> self.max_buffer_size:
+ # We've hit max_buffer_size. We have to accept a
+ # partial write and cut back our buffer.
+ overage = len(self._write_buf) - self.max_buffer_size
+ self._write_buf = self._write_buf[:self.max_buffer_size]
+ raise BlockingIOError(e.errno, e.strerror, overage)
+ return written
 
 def truncate(self, pos=None):
- self.flush()
- if pos is None:
- pos = self.raw.tell()
- return self.raw.truncate(pos)
+ with self._write_lock:
+ self._flush_unlocked()
+ if pos is None:
+ pos = self.raw.tell()
+ return self.raw.truncate(pos)
 
 def flush(self):
+ with self._write_lock:
+ self._flush_unlocked()
+ 
+ def _flush_unlocked(self):
 if self.closed:
 raise ValueError("flush of closed file")
 written = 0
@@ -1077,8 +1086,9 @@ class BufferedWriter(_BufferedIOMixin):
 return self.raw.tell() + len(self._write_buf)
 
 def seek(self, pos, whence=0):
- self.flush()
- return self.raw.seek(pos, whence)
+ with self._write_lock:
+ self._flush_unlocked()
+ return self.raw.seek(pos, whence)
 
 
 class BufferedRWPair(BufferedIOBase):
diff -r 02b8a061203a Lib/test/test_io.py
--- a/Lib/test/test_io.py	Thu Aug 14 17:56:07 2008 +0200
+++ b/Lib/test/test_io.py	Thu Aug 14 21:20:29 2008 +0200
@@ -6,6 +6,7 @@ import sys
 import sys
 import time
 import array
+import threading
 import unittest
 from itertools import chain
 from test import test_support
@@ -445,6 +446,38 @@ class BufferedWriterTest(unittest.TestCa
 bufio.flush()
 
 self.assertEquals(b"abc", writer._write_stack[0])
+
+ def testThreads(self):
+ # BufferedWriter should not raise exceptions or crash
+ # when called from multiple threads.
+ try:
+ # We use a real file object because it allows us to
+ # exercise situations where the GIL is released before
+ # writing the buffer to the raw streams. This is in addition
+ # to concurrency issues due to switching threads in the middle
+ # of Python code.
+ with io.open(test_support.TESTFN, "wb", buffering=0) as raw:
+ bufio = io.BufferedWriter(raw, 8)
+ errors = []
+ def f():
+ try:
+ # Write enough bytes to flush the buffer
+ s = b"a" * 19
+ for i in range(50):
+ bufio.write(s)
+ except Exception as e:
+ errors.append(e)
+ raise
+ threads = [threading.Thread(target=f) for x in range(20)]
+ for t in threads:
+ t.start()
+ time.sleep(0.02) # yield
+ for t in threads:
+ t.join()
+ self.assertFalse(errors,
+ "the following exceptions were caught: %r" % errors)
+ finally:
+ test_support.unlink(test_support.TESTFN)
 
 
 class BufferedRWPairTest(unittest.TestCase):
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