data race on hashing of datetime objects

[kumaraditya303]

Currently hashes of datetime objects are computed lazily as such it causes tsan warning as it is stored non-atomically.

TSAN race:

WARNING: ThreadSanitizer: data race (pid=58514)
  Read of size 8 at 0x0001104978a0 by thread T18094:
    #0 datetime_hash _datetimemodule.c:6603 (python.exe:arm64+0x1003b3cbc)
    #1 PyObject_Hash object.c (python.exe:arm64+0x10012b4d8)
    #2 setitem_take2_lock_held dictobject.c:2661 (python.exe:arm64+0x1000fb300)
    #3 _PyDict_FromItems dictobject.c:2255 (python.exe:arm64+0x1000f9b54)
    #4 _PyEval_EvalFrameDefault generated_cases.c.h:1272 (python.exe:arm64+0x10027634c)
    #5 _PyEval_Vector ceval.c:1989 (python.exe:arm64+0x10026ad88)
    #6 _PyFunction_Vectorcall call.c (python.exe:arm64+0x10007fcec)
    #7 method_vectorcall classobject.c:65 (python.exe:arm64+0x100084190)
    #8 _PyObject_Call call.c:348 (python.exe:arm64+0x10007f8b0)
    #9 PyObject_Call call.c:373 (python.exe:arm64+0x10007f9d8)
    #10 _PyEval_EvalFrameDefault generated_cases.c.h:2616 (python.exe:arm64+0x10027bf64)
    #11 _PyEval_Vector ceval.c:1989 (python.exe:arm64+0x10026ad88)
    #12 _PyFunction_Vectorcall call.c (python.exe:arm64+0x10007fcec)
    #13 method_vectorcall classobject.c:73 (python.exe:arm64+0x10008422c)
    #14 context_run context.c:728 (python.exe:arm64+0x1002b53dc)
    #15 _PyEval_EvalFrameDefault generated_cases.c.h:3710 (python.exe:arm64+0x10027ffbc)
    #16 _PyEval_Vector ceval.c:1989 (python.exe:arm64+0x10026ad88)
    #17 _PyFunction_Vectorcall call.c (python.exe:arm64+0x10007fcec)
    #18 method_vectorcall classobject.c:73 (python.exe:arm64+0x10008422c)
    #19 _PyObject_Call call.c:348 (python.exe:arm64+0x10007f964)
    #20 PyObject_Call call.c:373 (python.exe:arm64+0x10007f9d8)
    #21 thread_run _threadmodule.c:387 (python.exe:arm64+0x10041b338)
    #22 pythread_wrapper thread_pthread.h:234 (python.exe:arm64+0x100358824)

  Previous write of size 8 at 0x0001104978a0 by thread T18096:
    #0 datetime_hash _datetimemodule.c:6629 (python.exe:arm64+0x1003b3f88)
    #1 PyObject_Hash object.c (python.exe:arm64+0x10012b4d8)
    #2 setitem_take2_lock_held dictobject.c:2661 (python.exe:arm64+0x1000fb300)
    #3 _PyDict_FromItems dictobject.c:2255 (python.exe:arm64+0x1000f9b54)
    #4 _PyEval_EvalFrameDefault generated_cases.c.h:1272 (python.exe:arm64+0x10027634c)
    #5 _PyEval_Vector ceval.c:1989 (python.exe:arm64+0x10026ad88)
    #6 _PyFunction_Vectorcall call.c (python.exe:arm64+0x10007fcec)
    #7 method_vectorcall classobject.c:65 (python.exe:arm64+0x100084190)
    #8 _PyObject_Call call.c:348 (python.exe:arm64+0x10007f8b0)
    #9 PyObject_Call call.c:373 (python.exe:arm64+0x10007f9d8)
    #10 _PyEval_EvalFrameDefault generated_cases.c.h:2616 (python.exe:arm64+0x10027bf64)
    #11 _PyEval_Vector ceval.c:1989 (python.exe:arm64+0x10026ad88)
    #12 _PyFunction_Vectorcall call.c (python.exe:arm64+0x10007fcec)
    #13 method_vectorcall classobject.c:73 (python.exe:arm64+0x10008422c)
    #14 context_run context.c:728 (python.exe:arm64+0x1002b53dc)
    #15 _PyEval_EvalFrameDefault generated_cases.c.h:3710 (python.exe:arm64+0x10027ffbc)
    #16 _PyEval_Vector ceval.c:1989 (python.exe:arm64+0x10026ad88)
    #17 _PyFunction_Vectorcall call.c (python.exe:arm64+0x10007fcec)
    #18 method_vectorcall classobject.c:73 (python.exe:arm64+0x10008422c)
    #19 _PyObject_Call call.c:348 (python.exe:arm64+0x10007f964)
    #20 PyObject_Call call.c:373 (python.exe:arm64+0x10007f9d8)
    #21 thread_run _threadmodule.c:387 (python.exe:arm64+0x10041b338)
    #22 pythread_wrapper thread_pthread.h:234 (python.exe:arm64+0x100358824)

Linked PRs

• gh-139774: use relaxed atomics for datetime hashes #139775
• [3.14] gh-139774: use relaxed atomics for datetime hashes (GH-139775) #139780