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bpo-43785: Improve BZ2File performance by removing RLock (GH-25299) 

Remove `RLock` from `BZ2File`. It makes `BZ2File` to thread unsafe, but
gzip and lzma don't use it too.

Co-authored-by: Gregory P. Smith <greg@krypto.org>
This commit is contained in:
Inada Naoki 2021-04-12 14:46:53 +09:00 committed by GitHub
parent 553ee2781a
commit cc2ffcdfd7
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 48 additions and 59 deletions
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103
Lib/bz2.py
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@ -13,7 +13,6 @@ from builtins import open as _builtin_open
import io
import os
import _compression
from threading import RLock
from _bz2 import BZ2Compressor, BZ2Decompressor
@ -53,9 +52,6 @@ class BZ2File(_compression.BaseStream):
If mode is 'r', the input file may be the concatenation of
multiple compressed streams.
"""
# This lock must be recursive, so that BufferedIOBase's
# writelines() does not deadlock.
self._lock = RLock()
self._fp = None
self._closefp = False
self._mode = _MODE_CLOSED
@ -104,24 +100,23 @@ class BZ2File(_compression.BaseStream):
May be called more than once without error. Once the file is
closed, any other operation on it will raise a ValueError.
"""
with self._lock:
if self._mode == _MODE_CLOSED:
return
if self._mode == _MODE_CLOSED:
return
try:
if self._mode == _MODE_READ:
self._buffer.close()
elif self._mode == _MODE_WRITE:
self._fp.write(self._compressor.flush())
self._compressor = None
finally:
try:
if self._mode == _MODE_READ:
self._buffer.close()
elif self._mode == _MODE_WRITE:
self._fp.write(self._compressor.flush())
self._compressor = None
if self._closefp:
self._fp.close()
finally:
try:
if self._closefp:
self._fp.close()
finally:
self._fp = None
self._closefp = False
self._mode = _MODE_CLOSED
self._buffer = None
self._fp = None
self._closefp = False
self._mode = _MODE_CLOSED
self._buffer = None
@property
def closed(self):
@ -153,12 +148,11 @@ class BZ2File(_compression.BaseStream):
Always returns at least one byte of data, unless at EOF.
The exact number of bytes returned is unspecified.
"""
with self._lock:
self._check_can_read()
# Relies on the undocumented fact that BufferedReader.peek()
# always returns at least one byte (except at EOF), independent
# of the value of n
return self._buffer.peek(n)
self._check_can_read()
# Relies on the undocumented fact that BufferedReader.peek()
# always returns at least one byte (except at EOF), independent
# of the value of n
return self._buffer.peek(n)
def read(self, size=-1):
"""Read up to size uncompressed bytes from the file.
@ -166,9 +160,8 @@ class BZ2File(_compression.BaseStream):
If size is negative or omitted, read until EOF is reached.
Returns b'' if the file is already at EOF.
"""
with self._lock:
self._check_can_read()
return self._buffer.read(size)
self._check_can_read()
return self._buffer.read(size)
def read1(self, size=-1):
"""Read up to size uncompressed bytes, while trying to avoid
@ -177,20 +170,18 @@ class BZ2File(_compression.BaseStream):
Returns b'' if the file is at EOF.
"""
with self._lock:
self._check_can_read()
if size < 0:
size = io.DEFAULT_BUFFER_SIZE
return self._buffer.read1(size)
self._check_can_read()
if size < 0:
size = io.DEFAULT_BUFFER_SIZE
return self._buffer.read1(size)
def readinto(self, b):
"""Read bytes into b.
Returns the number of bytes read (0 for EOF).
"""
with self._lock:
self._check_can_read()
return self._buffer.readinto(b)
self._check_can_read()
return self._buffer.readinto(b)
def readline(self, size=-1):
"""Read a line of uncompressed bytes from the file.
@ -203,9 +194,8 @@ class BZ2File(_compression.BaseStream):
if not hasattr(size, "__index__"):
raise TypeError("Integer argument expected")
size = size.__index__()
with self._lock:
self._check_can_read()
return self._buffer.readline(size)
self._check_can_read()
return self._buffer.readline(size)
def readlines(self, size=-1):
"""Read a list of lines of uncompressed bytes from the file.
@ -218,9 +208,8 @@ class BZ2File(_compression.BaseStream):
if not hasattr(size, "__index__"):
raise TypeError("Integer argument expected")
size = size.__index__()
with self._lock:
self._check_can_read()
return self._buffer.readlines(size)
self._check_can_read()
return self._buffer.readlines(size)
def write(self, data):
"""Write a byte string to the file.
@ -229,12 +218,11 @@ class BZ2File(_compression.BaseStream):
always len(data). Note that due to buffering, the file on disk
may not reflect the data written until close() is called.
"""
with self._lock:
self._check_can_write()
compressed = self._compressor.compress(data)
self._fp.write(compressed)
self._pos += len(data)
return len(data)
self._check_can_write()
compressed = self._compressor.compress(data)
self._fp.write(compressed)
self._pos += len(data)
return len(data)
def writelines(self, seq):
"""Write a sequence of byte strings to the file.
@ -244,8 +232,7 @@ class BZ2File(_compression.BaseStream):
Line separators are not added between the written byte strings.
"""
with self._lock:
return _compression.BaseStream.writelines(self, seq)
return _compression.BaseStream.writelines(self, seq)
def seek(self, offset, whence=io.SEEK_SET):
"""Change the file position.
@ -262,17 +249,15 @@ class BZ2File(_compression.BaseStream):
Note that seeking is emulated, so depending on the parameters,
this operation may be extremely slow.
"""
with self._lock:
self._check_can_seek()
return self._buffer.seek(offset, whence)
self._check_can_seek()
return self._buffer.seek(offset, whence)
def tell(self):
"""Return the current file position."""
with self._lock:
self._check_not_closed()
if self._mode == _MODE_READ:
return self._buffer.tell()
return self._pos
self._check_not_closed()
if self._mode == _MODE_READ:
return self._buffer.tell()
return self._pos
def open(filename, mode="rb", compresslevel=9,

4
Misc/NEWS.d/next/Library/2021-04-09-14-51-58.bpo-43785.1mM5xE.rst Normal file
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@ -0,0 +1,4 @@
Improve ``bz2.BZ2File`` performance by removing the RLock from BZ2File.
This makes BZ2File thread unsafe in the face of multiple simultaneous
readers or writers, just like its equivalent classes in :mod:`gzip` and
:mod:`lzma` have always been. Patch by Inada Naoki.