Thread-safety for linecache

Author: vfdev-5

Lib/linecache.py

@@ -4,6 +4,7 @@
 is not found, it will look down the module search path for a file by
 that name.
 """
+import threading
 
 __all__ = ["getline", "clearcache", "checkcache", "lazycache"]
 
@@ -12,6 +13,7 @@
 # or a tuple (size, mtime, lines, fullname) once loaded.
 cache = {}
 _interactive_cache = {}
+mutex = threading.Lock()
 
 
 def clearcache():
@@ -33,10 +35,9 @@ 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 +57,9 @@ 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 +84,8 @@ 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
@@ -125,8 +121,9 @@ 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:
+    with mutex:
+        entry = cache.get(filename, None)
+        if entry is not None and len(entry) != 1:
             cache.pop(filename, None)
     if _source_unavailable(filename):
         return []
@@ -156,13 +153,14 @@ 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.
@@ -211,11 +209,9 @@ 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
     if not filename or (filename.startswith('<') and filename.endswith('>')):
         return False
     # Try for a __loader__, if available
@@ -245,4 +241,5 @@ 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