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gh-117657: Fix data races when writing / reading ob_gc_bits #118292

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Merged
merged 4 commits into from
May 8, 2024
Merged

gh-117657: Fix data races when writing / reading ob_gc_bits #118292

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b9ffd58
Fix data races when writing / reading `ob_gc_bits`
mpage Apr 25, 2024
ae8e5b8
Fix comment and remove suppressions
mpage Apr 25, 2024
f2475b8
Merge branch 'main' into gh-117657-tsan-gc-bits
mpage May 6, 2024
3f354eb
Use new locking discipline
mpage May 6, 2024
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Use new locking discipline
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@mpage
mpage committed May 6, 2024
commit 3f354ebabb8507ad9f179dc288e012947cd62c39
15 changes: 0 additions & 15 deletions 15 Include/cpython/pyatomic.h
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Original file line number Diff line number Diff line change
Expand Up @@ -250,14 +250,6 @@ static inline uintptr_t
_Py_atomic_and_uintptr(uintptr_t *obj, uintptr_t value);


// --- _Py_atomic_and_relaxed ------------------------------------------------
// Performs `*obj &= value` atomically and returns the previous value of `*obj`
// (relaxed consistency).

static inline uint8_t
_Py_atomic_and_uint8_relaxed(uint8_t *obj, uint8_t value);


// --- _Py_atomic_or ---------------------------------------------------------
// Performs `*obj |= value` atomically and returns the previous value of `*obj`.

Expand All @@ -277,13 +269,6 @@ static inline uintptr_t
_Py_atomic_or_uintptr(uintptr_t *obj, uintptr_t value);


// --- _Py_atomic_or_relaxed -------------------------------------------------
// Performs `*obj |= value` atomically and returns the previous value of `*obj`
// (relaxed consistency).

static inline uint8_t
_Py_atomic_or_uint8_relaxed(uint8_t *obj, uint8_t value);

// --- _Py_atomic_load -------------------------------------------------------
// Atomically loads `*obj` (sequential consistency)

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16 changes: 0 additions & 16 deletions 16 Include/cpython/pyatomic_gcc.h
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Expand Up @@ -218,13 +218,6 @@ _Py_atomic_and_uintptr(uintptr_t *obj, uintptr_t value)
{ return __atomic_fetch_and(obj, value, __ATOMIC_SEQ_CST); }


// --- _Py_atomic_and_relaxed ------------------------------------------------

static inline uint8_t
_Py_atomic_and_uint8_relaxed(uint8_t *obj, uint8_t value)
{ return __atomic_fetch_and(obj, value, __ATOMIC_RELAXED); }


// --- _Py_atomic_or ---------------------------------------------------------

static inline uint8_t
Expand All @@ -248,15 +241,6 @@ _Py_atomic_or_uintptr(uintptr_t *obj, uintptr_t value)
{ return __atomic_fetch_or(obj, value, __ATOMIC_SEQ_CST); }


// --- _Py_atomic_or_relaxed -------------------------------------------------

static inline uint8_t
_Py_atomic_or_uint8_relaxed(uint8_t *obj, uint8_t value)
{
return __atomic_fetch_or(obj, value, __ATOMIC_RELAXED);
}


// --- _Py_atomic_load -------------------------------------------------------

static inline int
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21 changes: 1 addition & 20 deletions 21 Include/cpython/pyatomic_msc.h
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Expand Up @@ -450,16 +450,6 @@ _Py_atomic_and_uintptr(uintptr_t *obj, uintptr_t value)
}


// --- _Py_atomic_and_relaxed ------------------------------------------------

static inline uint8_t
_Py_atomic_and_uint8_relaxed(uint8_t *obj, uint8_t value)
{
_Py_atomic_ASSERT_ARG_TYPE(char);
return (uint8_t)_InterlockedAnd8NoFence((volatile char *)obj, (char)value);
}


// --- _Py_atomic_or ---------------------------------------------------------

static inline uint8_t
Expand Down Expand Up @@ -500,6 +490,7 @@ _Py_atomic_or_uint64(uint64_t *obj, uint64_t value)
#endif
}


static inline uintptr_t
_Py_atomic_or_uintptr(uintptr_t *obj, uintptr_t value)
{
Expand All @@ -515,16 +506,6 @@ _Py_atomic_or_uintptr(uintptr_t *obj, uintptr_t value)
}


// --- _Py_atomic_or_relaxed -------------------------------------------------

static inline uint8_t
_Py_atomic_or_uint8_relaxed(uint8_t *obj, uint8_t value)
{
_Py_atomic_ASSERT_ARG_TYPE(char);
return (uint8_t)_InterlockedOr8NoFence((volatile char *)obj, (char)value);
}


// --- _Py_atomic_load -------------------------------------------------------

static inline uint8_t
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20 changes: 0 additions & 20 deletions 20 Include/cpython/pyatomic_std.h
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Expand Up @@ -366,16 +366,6 @@ _Py_atomic_and_uintptr(uintptr_t *obj, uintptr_t value)
}


// --- _Py_atomic_and_relaxed ------------------------------------------------

static inline uint8_t
_Py_atomic_and_uint8_relaxed(uint8_t *obj, uint8_t value)
{
_Py_USING_STD;
return atomic_fetch_and_explicit((_Atomic(uint8_t)*)obj, value, memory_order_relaxed);
}


// --- _Py_atomic_or ---------------------------------------------------------

static inline uint8_t
Expand Down Expand Up @@ -414,16 +404,6 @@ _Py_atomic_or_uintptr(uintptr_t *obj, uintptr_t value)
}


// --- _Py_atomic_or_relaxed -------------------------------------------------

static inline uint8_t
_Py_atomic_or_uint8_relaxed(uint8_t *obj, uint8_t value)
{
_Py_USING_STD;
return atomic_fetch_or_explicit((_Atomic(uint8_t)*)obj, value, memory_order_relaxed);
}


// --- _Py_atomic_load -------------------------------------------------------

static inline int
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20 changes: 15 additions & 5 deletions 20 Include/internal/pycore_gc.h
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Expand Up @@ -37,7 +37,15 @@ static inline PyObject* _Py_FROM_GC(PyGC_Head *gc) {
}


/* Bit flags for ob_gc_bits (in Py_GIL_DISABLED builds) */
/* Bit flags for ob_gc_bits (in Py_GIL_DISABLED builds)
*
* Setting the bits requires a relaxed store. The per-object lock must also be
* held, except when the object is only visible to a single thread (e.g. during
* object initialization or destruction).
*
* Reading the bits requires using a relaxed load, but does not require holding
* the per-object lock.
*/
#ifdef Py_GIL_DISABLED
# define _PyGC_BITS_TRACKED (1) // Tracked by the GC
# define _PyGC_BITS_FINALIZED (2) // tp_finalize was called
Expand All @@ -51,9 +59,10 @@ static inline PyObject* _Py_FROM_GC(PyGC_Head *gc) {
#ifdef Py_GIL_DISABLED

static inline void
_PyObject_SET_GC_BITS(PyObject *op, uint8_t bits)
_PyObject_SET_GC_BITS(PyObject *op, uint8_t new_bits)
{
_Py_atomic_or_uint8_relaxed(&op->ob_gc_bits, bits);
uint8_t bits = _Py_atomic_load_uint8_relaxed(&op->ob_gc_bits);
_Py_atomic_store_uint8_relaxed(&op->ob_gc_bits, bits | new_bits);
}

static inline int
Expand All @@ -63,9 +72,10 @@ _PyObject_HAS_GC_BITS(PyObject *op, uint8_t bits)
}

static inline void
_PyObject_CLEAR_GC_BITS(PyObject *op, uint8_t bits)
_PyObject_CLEAR_GC_BITS(PyObject *op, uint8_t bits_to_clear)
{
_Py_atomic_and_uint8_relaxed(&op->ob_gc_bits, ~bits);
uint8_t bits = _Py_atomic_load_uint8_relaxed(&op->ob_gc_bits);
_Py_atomic_store_uint8_relaxed(&op->ob_gc_bits, bits & ~bits_to_clear);
}

#endif
Expand Down
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