gh-116738: Add critical section to dbm/gdbm context manager

[yoney]

Add Py_{BEGIN,END}_CRITICAL_SECTION() to the context managers in the dbm and gdbm modules for the free threading build. Other methods are already covered.

This could be a problem in a rare corner case if a thread outlives the context manager's scope. I created a local test, and TSAN identifies the issue.

deftest_context_manager(self): defworker(db): db.close() withos_helper.temp_dir() astmpdirname: withgdbm.open(f"{tmpdirname}/gdbm_filename", "c") asdb: t1=threading.Thread(target=worker, args=(db,)) t1.start() t1.join()

WARNING: ThreadSanitizer: data race (pid=1672837) Read of size 8 at 0x7f9fdb330e48 by thread T1: #0 _gdbm_gdbm_close_impl /home/alper/workspace/tsan/./Modules/_gdbmmodule.c:413:15 (_gdbm.cpython-315td-x86_64-linux-gnu.so+0x2ce1) (BuildId: 42fff9900c3973fef01c9a778b42049ab0110b9f) #1 _gdbm_gdbm_close /home/alper/workspace/tsan/./Modules/clinic/_gdbmmodule.c.h:100:20 (_gdbm.cpython-315td-x86_64-linux-gnu.so+0x2ce1) #2 method_vectorcall_NOARGS /home/alper/workspace/tsan/Objects/descrobject.c:448:24 (python+0x5c662b) (BuildId: 89128bd333556519224b9af239856b3fcb80f8ab) ... Previous write of size 8 at 0x7f9fdb330e48 by main thread: #0 _gdbm_gdbm_close_impl /home/alper/workspace/tsan/./Modules/_gdbmmodule.c:416:18 (_gdbm.cpython-315td-x86_64-linux-gnu.so+0x4944) (BuildId: 42fff9900c3973fef01c9a778b42049ab0110b9f) #1 gdbm__exit__ /home/alper/workspace/tsan/./Modules/_gdbmmodule.c:693:12 (_gdbm.cpython-315td-x86_64-linux-gnu.so+0x4944) #2 method_vectorcall_VARARGS /home/alper/workspace/tsan/Objects/descrobject.c:325:24 (python+0x5c5ef9) (BuildId: 89128bd333556519224b9af239856b3fcb80f8ab) ... SUMMARY: ThreadSanitizer: data race /home/alper/workspace/tsan/./Modules/_gdbmmodule.c:413:15 in _gdbm_gdbm_close_impl ================== 

cc: @mpage@colesbury

• Issue: Audit all built-in modules for thread safety #116738

[serhiy-storchaka]

LGTM. 👍

[colesbury]

LGTM as well.

FYI, you can also use Argument Clinic for __enter__ and __exit__ functions now if you prefer Argument Clinic boilerplate to Py_BEGIN_CRITICAL_SECTION boilerplate.

[miss-islington-app]

Thanks @yoney for the PR, and @colesbury for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-140459 is a backport of this pull request to the 3.14 branch.