https://github.com/python/cpython/commit/ee4fe00a8f72ea84a421bb626d7c78335c5c9ea1
commit: ee4fe00a8f72ea84a421bb626d7c78335c5c9ea1
branch: main
author: Donghee Na <[email protected]>
committer: corona10 <[email protected]>
date: 2026-08-13T00:12:39Z
summary:
gh-129752: Don't update adaptive counters when TLBC=0 in free-threading.
(gh-155497)
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2026-08-11-01-45-24.gh-issue-129752.Zo3OUx.rst
M Include/internal/pycore_backoff.h
M Lib/test/test_thread_local_bytecode.py
M Python/ceval_macros.h
diff --git a/Include/internal/pycore_backoff.h
b/Include/internal/pycore_backoff.h
index 38dd82f6fc8a140..9d1912cc28921c3 100644
--- a/Include/internal/pycore_backoff.h
+++ b/Include/internal/pycore_backoff.h
@@ -108,6 +108,12 @@ backoff_counter_triggers(_Py_BackoffCounter counter)
return counter.value_and_backoff < UNREACHABLE_BACKOFF;
}
+static inline bool
+backoff_counter_is_unreachable(_Py_BackoffCounter counter)
+{
+ return (counter.value_and_backoff & BACKOFF_MASK) == UNREACHABLE_BACKOFF;
+}
+
static inline _Py_BackoffCounter
trigger_backoff_counter(void)
{
diff --git a/Lib/test/test_thread_local_bytecode.py
b/Lib/test/test_thread_local_bytecode.py
index 6a1ae4064b5daf1..6f76f1bc33561fb 100644
--- a/Lib/test/test_thread_local_bytecode.py
+++ b/Lib/test/test_thread_local_bytecode.py
@@ -108,7 +108,6 @@ def f(a, b, q=None):
""")
assert_python_ok("-X", "tlbc=1", "-c", code)
- @support.skip_if_sanitizer("gh-129752: data race on adaptive counter",
thread=True)
def test_no_copies_if_tlbc_disabled(self):
code = textwrap.dedent("""
import queue
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2026-08-11-01-45-24.gh-issue-129752.Zo3OUx.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2026-08-11-01-45-24.gh-issue-129752.Zo3OUx.rst
new file mode 100644
index 000000000000000..aad13dc0adef34f
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2026-08-11-01-45-24.gh-issue-129752.Zo3OUx.rst
@@ -0,0 +1,2 @@
+Don't update adaptive counters in the free-threaded build when thread-local
+bytecode is disabled (``-X tlbc=0``). Patch by Donghee Na.
diff --git a/Python/ceval_macros.h b/Python/ceval_macros.h
index f19adfa0cfcfc15..36921e35533433d 100644
--- a/Python/ceval_macros.h
+++ b/Python/ceval_macros.h
@@ -354,6 +354,25 @@ static void dtrace_function_return(_PyInterpreterFrame *);
#define ADAPTIVE_COUNTER_TRIGGERS(COUNTER) \
backoff_counter_triggers(forge_backoff_counter((COUNTER)))
+#ifdef Py_GIL_DISABLED
+/* Counters are unreachable when thread-local bytecode is disabled,
+ * so there is no need to update them. */
+#define ADVANCE_ADAPTIVE_COUNTER(COUNTER) \
+ do { \
+ _Py_BackoffCounter cnt = (COUNTER); \
+ if (!backoff_counter_is_unreachable(cnt)) { \
+ (COUNTER) = advance_backoff_counter(cnt); \
+ } \
+ } while (0);
+
+#define PAUSE_ADAPTIVE_COUNTER(COUNTER) \
+ do { \
+ _Py_BackoffCounter cnt = (COUNTER); \
+ if (!backoff_counter_is_unreachable(cnt)) { \
+ (COUNTER) = pause_backoff_counter(cnt); \
+ } \
+ } while (0);
+#else
#define ADVANCE_ADAPTIVE_COUNTER(COUNTER) \
do { \
(COUNTER) = advance_backoff_counter((COUNTER)); \
@@ -363,6 +382,7 @@ static void dtrace_function_return(_PyInterpreterFrame *);
do { \
(COUNTER) = pause_backoff_counter((COUNTER)); \
} while (0);
+#endif
#ifdef ENABLE_SPECIALIZATION
/* Multiple threads may execute these concurrently if thread-local bytecode is
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