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gh-112075: Iterating a dict shouldn't require locks by DinoV · Pull Request #115108 · python/cpython · GitHub
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gh-112075: Iterating a dict shouldn't require locks #115108

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Merged
DinoV merged 7 commits into from
Feb 22, 2024
Merged

gh-112075: Iterating a dict shouldn't require locks #115108

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afddb70
Thread safe lock-free iteration
DinoV Feb 1, 2024
39bc495
Don't use atomics for iteratio and allow multiple threads to race on …
DinoV Feb 16, 2024
902ce67
Fixup ifdef/ifndef
DinoV Feb 16, 2024
0ba2f5d
Use has_unique_reference
DinoV Feb 16, 2024
042cf26
Less atomics
DinoV Feb 21, 2024
a079a6d
Fix style issues
DinoV Feb 21, 2024
a1d7718
acquire_key_value returns -1 and 0
DinoV Feb 22, 2024
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Use has_unique_reference
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@DinoV
DinoV committed Feb 22, 2024
commit 0ba2f5d439f693ee2dd8085de9e6eaef649e10e7
28 changes: 13 additions & 15 deletions Objects/dictobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5428,13 +5428,23 @@ dictiter_iternext_threadsafe(PyDictObject *d, PyObject *self,

#endif

static bool
has_unique_reference(PyObject *op)
{
#ifdef Py_GIL_DISABLED
return (_Py_IsOwnedByCurrentThread(op) &&
op->ob_ref_local == 1 &&
_Py_atomic_load_ssize_relaxed(&op->ob_ref_shared) == 0);
#else
return Py_REFCNT(op) == 1;
#endif
}

static bool
acquire_iter_result(PyObject *result)
{
#ifdef Py_GIL_DISABLED
if (_Py_IsOwnedByCurrentThread(result) &&
result->ob_ref_local == 1 &&
_Py_atomic_load_ssize_relaxed(&result->ob_ref_shared) == 0) {
if (has_unique_reference(result)) {
#else
if (Py_REFCNT(result) == 1) {
#endif
Expand Down Expand Up @@ -6647,18 +6657,6 @@ _PyObject_MakeDictFromInstanceAttributes(PyObject *obj, PyDictValues *values)
return make_dict_from_instance_attributes(interp, keys, values);
}

static bool
has_unique_reference(PyObject *op)
{
#ifdef Py_GIL_DISABLED
return (_Py_IsOwnedByCurrentThread(op) &&
op->ob_ref_local == 1 &&
_Py_atomic_load_ssize_relaxed(&op->ob_ref_shared) == 0);
#else
return Py_REFCNT(op) == 1;
#endif
}

// Return true if the dict was dematerialized, false otherwise.
bool
_PyObject_MakeInstanceAttributesFromDict(PyObject *obj, PyDictOrValues *dorv)
Expand Down