Cutlery/calibre
1
0
Fork 0
mirror of https://github.com/kovidgoyal/calibre.git synced 2025-07-09 03:04:10 -04:00
Code Issues Packages Projects Releases Wiki Activity

Ensure that updating the vl_book cache is both thread safe and recursion safe.

Browse Source
This commit is contained in:
Charles Haley 2021-05-05 18:59:45 +01:00
parent 0a6010e712
commit 312e44dc3b
1 changed files with 31 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
src/calibre/db/cache.py
View File

@ -15,6 +15,7 @@ import traceback
from collections import MutableSet, Set, defaultdict from collections import MutableSet, Set, defaultdict
from functools import partial, wraps from functools import partial, wraps
from io import BytesIO from io import BytesIO
from threading import Lock
from time import time from time import time
from calibre import as_unicode, isbytestring from calibre import as_unicode, isbytestring
@ -142,7 +143,7 @@ class Cache(object):
self.formatter_template_cache = {} self.formatter_template_cache = {}
self.dirtied_cache = {} self.dirtied_cache = {}
self.vls_for_books_cache = None self.vls_for_books_cache = None
self.vls_for_books_cache_is_loading = False self.vls_cache_lock = Lock()
self.dirtied_sequence = 0 self.dirtied_sequence = 0
self.cover_caches = set() self.cover_caches = set()
self.clear_search_cache_count = 0 self.clear_search_cache_count = 0
@ -252,7 +253,6 @@ class Cache(object):
self.clear_search_cache_count += 1 self.clear_search_cache_count += 1
self._search_api.update_or_clear(self, book_ids) self._search_api.update_or_clear(self, book_ids)
self.vls_for_books_cache = None self.vls_for_books_cache = None
self.vls_for_books_cache_is_loading = False
@read_api @read_api
def last_modified(self): def last_modified(self):
@ -2232,12 +2232,18 @@ class Cache(object):
if self.vls_for_books_cache is None: if self.vls_for_books_cache is None:
# Using a list is slightly faster than a set. # Using a list is slightly faster than a set.
c = defaultdict(list) c = defaultdict(list)
if self.vls_for_books_cache_is_loading: got_lock = False
try:
# use a primitive lock to ensure that only one thread is updating
# the cache and that recursive calls don't do the update. This
# method can recurse via self._search()
got_lock = self.vls_cache_lock.acquire(blocking=False)
if not got_lock:
# We get here if resolving the books in a VL triggers another VL # We get here if resolving the books in a VL triggers another VL
# calculation. This can be 'real' recursion, in which case the # calculation. This can be 'real' recursion, in which case the
# eventual answer will be wrong. It can also be a search using # eventual answer will be wrong. It can also be a search using
# a location of 'all' that causes evaluation of a composite that # a location of 'all' that causes evaluation of a composite that
# references virtual libraries. If the composite isn't used in a # references virtual_libraries(). If the composite isn't used in a
# VL then the eventual answer will be correct because get_metadata # VL then the eventual answer will be correct because get_metadata
# will clear the caches. # will clear the caches.
return c return c
@ -2252,6 +2258,9 @@ class Cache(object):
if book: if book:
c[book].append(_('[Error in Virtual library {0}: {1}]').format(lib, str(e))) c[book].append(_('[Error in Virtual library {0}: {1}]').format(lib, str(e)))
self.vls_for_books_cache = {b:tuple(sorted(libs, key=sort_key)) for b, libs in c.items()} self.vls_for_books_cache = {b:tuple(sorted(libs, key=sort_key)) for b, libs in c.items()}
finally:
if got_lock:
self.vls_cache_lock.release()
if not book_ids: if not book_ids:
book_ids = self._all_book_ids() book_ids = self._all_book_ids()
# book_ids is usually 1 long. The loop will be faster than a comprehension # book_ids is usually 1 long. The loop will be faster than a comprehension