https://github.com/python/cpython/commit/8054184f9f32c7ba561e6e23b358074824e4928d
commit: 8054184f9f32c7ba561e6e23b358074824e4928d
branch: main
author: vfdev <vfde...@gmail.com>
committer: kumaraditya303 <kumaradi...@python.org>
date: 2025-05-09T12:15:16+05:30
summary:
gh-133253: making linecache thread-safe (#133305)
Co-authored-by: Sam Gross <colesb...@gmail.com>
files:
A Misc/NEWS.d/next/Library/2025-05-05-10-41-41.gh-issue-133253.J5-xDD.rst
M Lib/linecache.py
M Lib/test/test_linecache.py
diff --git a/Lib/linecache.py b/Lib/linecache.py
index 87d7d6fda657e4..ef73d1aa99774a 100644
--- a/Lib/linecache.py
+++ b/Lib/linecache.py
@@ -33,10 +33,9 @@ def getlines(filename, module_globals=None):
"""Get the lines for a Python source file from the cache.
Update the cache if it doesn't contain an entry for this file already."""
- if filename in cache:
- entry = cache[filename]
- if len(entry) != 1:
- return cache[filename][2]
+ entry = cache.get(filename, None)
+ if entry is not None and len(entry) != 1:
+ return entry[2]
try:
return updatecache(filename, module_globals)
@@ -56,10 +55,9 @@ def _make_key(code):
def _getlines_from_code(code):
code_id = _make_key(code)
- if code_id in _interactive_cache:
- entry = _interactive_cache[code_id]
- if len(entry) != 1:
- return _interactive_cache[code_id][2]
+ entry = _interactive_cache.get(code_id, None)
+ if entry is not None and len(entry) != 1:
+ return entry[2]
return []
@@ -84,12 +82,8 @@ def checkcache(filename=None):
filenames = [filename]
for filename in filenames:
- try:
- entry = cache[filename]
- except KeyError:
- continue
-
- if len(entry) == 1:
+ entry = cache.get(filename, None)
+ if entry is None or len(entry) == 1:
# lazy cache entry, leave it lazy.
continue
size, mtime, lines, fullname = entry
@@ -125,9 +119,7 @@ def updatecache(filename, module_globals=None):
# These import can fail if the interpreter is shutting down
return []
- if filename in cache:
- if len(cache[filename]) != 1:
- cache.pop(filename, None)
+ entry = cache.pop(filename, None)
if _source_unavailable(filename):
return []
@@ -146,9 +138,12 @@ def updatecache(filename, module_globals=None):
# Realise a lazy loader based lookup if there is one
# otherwise try to lookup right now.
- if lazycache(filename, module_globals):
+ lazy_entry = entry if entry is not None and len(entry) == 1 else None
+ if lazy_entry is None:
+ lazy_entry = _make_lazycache_entry(filename, module_globals)
+ if lazy_entry is not None:
try:
- data = cache[filename][0]()
+ data = lazy_entry[0]()
except (ImportError, OSError):
pass
else:
@@ -156,13 +151,14 @@ def updatecache(filename, module_globals=None):
# No luck, the PEP302 loader cannot find the source
# for this module.
return []
- cache[filename] = (
+ entry = (
len(data),
None,
[line + '\n' for line in data.splitlines()],
fullname
)
- return cache[filename][2]
+ cache[filename] = entry
+ return entry[2]
# Try looking through the module search path, which is only useful
# when handling a relative filename.
@@ -211,13 +207,20 @@ def lazycache(filename, module_globals):
get_source method must be found, the filename must be a cacheable
filename, and the filename must not be already cached.
"""
- if filename in cache:
- if len(cache[filename]) == 1:
- return True
- else:
- return False
+ entry = cache.get(filename, None)
+ if entry is not None:
+ return len(entry) == 1
+
+ lazy_entry = _make_lazycache_entry(filename, module_globals)
+ if lazy_entry is not None:
+ cache[filename] = lazy_entry
+ return True
+ return False
+
+
+def _make_lazycache_entry(filename, module_globals):
if not filename or (filename.startswith('<') and filename.endswith('>')):
- return False
+ return None
# Try for a __loader__, if available
if module_globals and '__name__' in module_globals:
spec = module_globals.get('__spec__')
@@ -230,9 +233,10 @@ def lazycache(filename, module_globals):
if name and get_source:
def get_lines(name=name, *args, **kwargs):
return get_source(name, *args, **kwargs)
- cache[filename] = (get_lines,)
- return True
- return False
+ return (get_lines,)
+ return None
+
+
def _register_code(code, string, name):
entry = (len(string),
@@ -245,4 +249,5 @@ def _register_code(code, string, name):
for const in code.co_consts:
if isinstance(const, type(code)):
stack.append(const)
- _interactive_cache[_make_key(code)] = entry
+ key = _make_key(code)
+ _interactive_cache[key] = entry
diff --git a/Lib/test/test_linecache.py b/Lib/test/test_linecache.py
index e4aa41ebb43762..02f65338428c8f 100644
--- a/Lib/test/test_linecache.py
+++ b/Lib/test/test_linecache.py
@@ -4,10 +4,12 @@
import unittest
import os.path
import tempfile
+import threading
import tokenize
from importlib.machinery import ModuleSpec
from test import support
from test.support import os_helper
+from test.support import threading_helper
from test.support.script_helper import assert_python_ok
@@ -374,5 +376,40 @@ def test_checkcache_with_no_parameter(self):
self.assertIn(self.unchanged_file, linecache.cache)
+class MultiThreadingTest(unittest.TestCase):
+ @threading_helper.reap_threads
+ @threading_helper.requires_working_threading()
+ def test_read_write_safety(self):
+
+ with tempfile.TemporaryDirectory() as tmpdirname:
+ filenames = []
+ for i in range(10):
+ name = os.path.join(tmpdirname, f"test_{i}.py")
+ with open(name, "w") as h:
+ h.write("import time\n")
+ h.write("import system\n")
+ filenames.append(name)
+
+ def linecache_get_line(b):
+ b.wait()
+ for _ in range(100):
+ for name in filenames:
+ linecache.getline(name, 1)
+
+ def check(funcs):
+ barrier = threading.Barrier(len(funcs))
+ threads = []
+
+ for func in funcs:
+ thread = threading.Thread(target=func, args=(barrier,))
+
+ threads.append(thread)
+
+ with threading_helper.start_threads(threads):
+ pass
+
+ check([linecache_get_line] * 20)
+
+
if __name__ == "__main__":
unittest.main()
diff --git
a/Misc/NEWS.d/next/Library/2025-05-05-10-41-41.gh-issue-133253.J5-xDD.rst
b/Misc/NEWS.d/next/Library/2025-05-05-10-41-41.gh-issue-133253.J5-xDD.rst
new file mode 100644
index 00000000000000..7009ca258bcabd
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-05-05-10-41-41.gh-issue-133253.J5-xDD.rst
@@ -0,0 +1 @@
+Fix thread-safety issues in :mod:`linecache`.
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