From: Kumar Aditya <kumaraditya@python.org>
Date: Thu, 24 Jul 2025 17:58:46 +0000 (+0530)
Subject: gh-136870: fix data races in instrumentation of bytecode (#136994)
X-Git-Tag: v3.15.0a1~857
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9a6b60af409d02468b935c569a4f49e88c399c4e;p=thirdparty%2FPython%2Fcpython.git

gh-136870: fix data races in instrumentation of bytecode (#136994)

De-instrumenting code objects modifies the thread local bytecode for all threads as such, holding the critical section on the code object is not sufficient and leads to data races. Now, the de-instrumentation is now performed under a stop the world pause as such no thread races with executing the thread local bytecode while it is being de-instrumented.
---

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-07-24-17-30-58.gh-issue-136870.ncx82J.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-07-24-17-30-58.gh-issue-136870.ncx82J.rst
new file mode 100644
index 000000000000..7552dc69169b
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-07-24-17-30-58.gh-issue-136870.ncx82J.rst
@@ -0,0 +1 @@
+Fix data races while de-instrumenting bytecode of code objects running concurrently in threads.
diff --git a/Python/instrumentation.c b/Python/instrumentation.c
index 44de480cd230..f9913cff402e 100644
--- a/Python/instrumentation.c
+++ b/Python/instrumentation.c
@@ -1190,9 +1190,10 @@ call_instrumentation_vector(
                 break;
             }
             else {
-                LOCK_CODE(code);
+                PyInterpreterState *interp = tstate->interp;
+                _PyEval_StopTheWorld(interp);
                 remove_tools(code, offset, event, 1 << tool);
-                UNLOCK_CODE();
+                _PyEval_StartTheWorld(interp);
             }
         }
     }
@@ -1381,9 +1382,10 @@ _Py_call_instrumentation_line(PyThreadState *tstate, _PyInterpreterFrame* frame,
         }
         else {
             /* DISABLE  */
-            LOCK_CODE(code);
+            PyInterpreterState *interp = tstate->interp;
+            _PyEval_StopTheWorld(interp);
             remove_line_tools(code, i, 1 << tool);
-            UNLOCK_CODE();
+            _PyEval_StartTheWorld(interp);
         }
     } while (tools);
     Py_DECREF(line_obj);
@@ -1438,9 +1440,10 @@ _Py_call_instrumentation_instruction(PyThreadState *tstate, _PyInterpreterFrame*
         }
         else {
             /* DISABLE  */
-            LOCK_CODE(code);
+            PyInterpreterState *interp = tstate->interp;
+            _PyEval_StopTheWorld(interp);
             remove_per_instruction_tools(code, offset, 1 << tool);
-            UNLOCK_CODE();
+            _PyEval_StartTheWorld(interp);
         }
     }
     Py_DECREF(offset_obj);
@@ -2995,9 +2998,10 @@ branch_handler_vectorcall(
             // Orphaned NOT_TAKEN -- Jump removed by the compiler
             return res;
         }
-        LOCK_CODE(code);
+        PyInterpreterState *interp = _PyInterpreterState_GET();
+        _PyEval_StopTheWorld(interp);
         remove_tools(code, offset, other_event, 1 << self->tool_id);
-        UNLOCK_CODE();
+        _PyEval_StartTheWorld(interp);
     }
     return res;
 }