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gh-117657: Fix small issues with instrumentation and TSAN #118064

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merged 1 commit into from
Apr 30, 2024
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gh-117657: Fix small issues with instrumentation and TSAN #118064

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11 changes: 9 additions & 2 deletions Include/internal/pycore_pyatomic_ft_wrappers.h
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,10 @@ extern "C" {
_Py_atomic_load_uint8(&value)
#define FT_ATOMIC_STORE_UINT8(value, new_value) \
_Py_atomic_store_uint8(&value, new_value)
#define FT_ATOMIC_LOAD_UINT8_RELAXED(value) \
_Py_atomic_load_uint8_relaxed(&value)
#define FT_ATOMIC_LOAD_UINT16_RELAXED(value) \
_Py_atomic_load_uint16_relaxed(&value)
#define FT_ATOMIC_STORE_PTR_RELAXED(value, new_value) \
_Py_atomic_store_ptr_relaxed(&value, new_value)
#define FT_ATOMIC_STORE_PTR_RELEASE(value, new_value) \
Expand All @@ -49,7 +53,8 @@ extern "C" {
_Py_atomic_store_ssize_relaxed(&value, new_value)
#define FT_ATOMIC_STORE_UINT8_RELAXED(value, new_value) \
_Py_atomic_store_uint8_relaxed(&value, new_value)

#define FT_ATOMIC_STORE_UINT16_RELAXED(value, new_value) \
_Py_atomic_store_uint16_relaxed(&value, new_value)
#else
#define FT_ATOMIC_LOAD_PTR(value) value
#define FT_ATOMIC_STORE_PTR(value, new_value) value = new_value
Expand All @@ -62,12 +67,14 @@ extern "C" {
#define FT_ATOMIC_LOAD_PTR_RELAXED(value) value
#define FT_ATOMIC_LOAD_UINT8(value) value
#define FT_ATOMIC_STORE_UINT8(value, new_value) value = new_value
#define FT_ATOMIC_LOAD_UINT8_RELAXED(value) value
#define FT_ATOMIC_LOAD_UINT16_RELAXED(value) value
#define FT_ATOMIC_STORE_PTR_RELAXED(value, new_value) value = new_value
#define FT_ATOMIC_STORE_PTR_RELEASE(value, new_value) value = new_value
#define FT_ATOMIC_STORE_UINTPTR_RELEASE(value, new_value) value = new_value
#define FT_ATOMIC_STORE_SSIZE_RELAXED(value, new_value) value = new_value
#define FT_ATOMIC_STORE_UINT8_RELAXED(value, new_value) value = new_value

#define FT_ATOMIC_STORE_UINT16_RELAXED(value, new_value) value = new_value
#endif

#ifdef __cplusplus
Expand Down
8 changes: 5 additions & 3 deletions Objects/genobject.c
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Expand Up @@ -11,6 +11,7 @@
#include "pycore_modsupport.h" // _PyArg_CheckPositional()
#include "pycore_object.h" // _PyObject_GC_UNTRACK()
#include "pycore_opcode_utils.h" // RESUME_AFTER_YIELD_FROM
#include "pycore_pyatomic_ft_wrappers.h" // FT_ATOMIC_*
#include "pycore_pyerrors.h" // _PyErr_ClearExcState()
#include "pycore_pystate.h" // _PyThreadState_GET()

Expand Down Expand Up @@ -329,10 +330,11 @@ gen_close_iter(PyObject *yf)
static inline bool
is_resume(_Py_CODEUNIT *instr)
{
uint8_t code = FT_ATOMIC_LOAD_UINT8_RELAXED(instr->op.code);
return (
instr->op.code == RESUME ||
instr->op.code == RESUME_CHECK ||
instr->op.code == INSTRUMENTED_RESUME
code == RESUME ||
code == RESUME_CHECK ||
code == INSTRUMENTED_RESUME
);
}

Expand Down
4 changes: 2 additions & 2 deletions Python/bytecodes.c
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Expand Up @@ -20,7 +20,7 @@
#include "pycore_object.h" // _PyObject_GC_TRACK()
#include "pycore_opcode_metadata.h" // uop names
#include "pycore_opcode_utils.h" // MAKE_FUNCTION_*
#include "pycore_pyatomic_ft_wrappers.h" // FT_ATOMIC_LOAD_PTR_ACQUIRE
#include "pycore_pyatomic_ft_wrappers.h" // FT_ATOMIC_*
#include "pycore_pyerrors.h" // _PyErr_GetRaisedException()
#include "pycore_pystate.h" // _PyInterpreterState_GET()
#include "pycore_range.h" // _PyRangeIterObject
Expand Down Expand Up @@ -163,7 +163,7 @@ dummy_func(
if ((oparg & RESUME_OPARG_LOCATION_MASK) < RESUME_AFTER_YIELD_FROM) {
CHECK_EVAL_BREAKER();
}
this_instr->op.code = RESUME_CHECK;
FT_ATOMIC_STORE_UINT8_RELAXED(this_instr->op.code, RESUME_CHECK);
}
}

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2 changes: 1 addition & 1 deletion Python/ceval.c
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@
#include "pycore_opcode_metadata.h" // EXTRA_CASES
#include "pycore_optimizer.h" // _PyUOpExecutor_Type
#include "pycore_opcode_utils.h" // MAKE_FUNCTION_*
#include "pycore_pyatomic_ft_wrappers.h" // FT_ATOMIC_LOAD_PTR_ACQUIRE
#include "pycore_pyatomic_ft_wrappers.h" // FT_ATOMIC_*
#include "pycore_pyerrors.h" // _PyErr_GetRaisedException()
#include "pycore_pystate.h" // _PyInterpreterState_GET()
#include "pycore_range.h" // _PyRangeIterObject
Expand Down
2 changes: 1 addition & 1 deletion Python/ceval_macros.h
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Expand Up @@ -150,7 +150,7 @@ GETITEM(PyObject *v, Py_ssize_t i) {
/* The integer overflow is checked by an assertion below. */
#define INSTR_OFFSET() ((int)(next_instr - _PyCode_CODE(_PyFrame_GetCode(frame))))
#define NEXTOPARG() do { \
_Py_CODEUNIT word = *next_instr; \
_Py_CODEUNIT word = {.cache = FT_ATOMIC_LOAD_UINT16_RELAXED(*(uint16_t*)next_instr)}; \
opcode = word.op.code; \
oparg = word.op.arg; \
} while (0)
Expand Down
2 changes: 1 addition & 1 deletion Python/generated_cases.c.h
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9 changes: 6 additions & 3 deletions Python/instrumentation.c
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Expand Up @@ -625,9 +625,10 @@ de_instrument(PyCodeObject *code, int i, int event)
return;
}
CHECK(_PyOpcode_Deopt[deinstrumented] == deinstrumented);
*opcode_ptr = deinstrumented;
FT_ATOMIC_STORE_UINT8_RELAXED(*opcode_ptr, deinstrumented);
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@mpage mpage Apr 19, 2024 •
edited
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Is relaxed strong enough? Do any consumers need to see the updates that are sequenced-before this store? Same comment applies to the below instances of using relaxed stores to update bytecode.

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In the deinstrumented case if we race and still see the instrumented opcode the data will still be there. In the instrumented case I think we do need some more synchronization around the tooling metadata, if we see the instrumented opcode before seeing the writes to the data that'll be bad.

I had originally had synchronizeds reads/writes around that in d8ea6bb#diff-adaefb7da847260ef7aff6e66007bc83f5b226c5389a23e1c9ea622c3b02c419 but the thought was that the synchronization around _PyFrame_GetCode(frame)->_co_instrumentation_version would be sufficient (which is in the latest version of #116775).

But that doesn't actually seem to be good enough - there's still some rare TSAN failures around the instrumentation data. But my plan is to push the synchronization there instead of on the opcode because I don't think we want to do acquire loads on the byte code which would be required to make a release write here meaningful.

if (_PyOpcode_Caches[deinstrumented]) {
instr[1].counter = adaptive_counter_warmup();
FT_ATOMIC_STORE_UINT16_RELAXED(instr[1].counter.as_counter,
adaptive_counter_warmup().as_counter);
}
}

Expand Down Expand Up @@ -702,8 +703,10 @@ instrument(PyCodeObject *code, int i)
int deopt = _PyOpcode_Deopt[opcode];
int instrumented = INSTRUMENTED_OPCODES[deopt];
assert(instrumented);
*opcode_ptr = instrumented;
FT_ATOMIC_STORE_UINT8_RELAXED(*opcode_ptr, instrumented);
if (_PyOpcode_Caches[deopt]) {
FT_ATOMIC_STORE_UINT16_RELAXED(instr[1].counter.as_counter,
adaptive_counter_warmup().as_counter);
instr[1].counter = adaptive_counter_warmup();
}
}
Expand Down
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