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

kumaraditya303 · web-flow · commit 9a6b60af409d · 2025-07-24T17:58:46.000Z
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
@@ -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
@@ -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;
 }

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+Fix data races while de-instrumenting bytecode of code objects running concurrently in threads.`
Original file line number	Diff line number	Diff line change
`@@ -1190,9 +1190,10 @@ call_instrumentation_vector(`
`1190`	`1190`	`break;`
`1191`	`1191`	`}`
`1192`	`1192`	`else {`
`1193`		`- LOCK_CODE(code);`
	`1193`	`+ PyInterpreterState *interp = tstate->interp;`
	`1194`	`+ _PyEval_StopTheWorld(interp);`
`1194`	`1195`	`remove_tools(code, offset, event, 1 << tool);`
`1195`		`- UNLOCK_CODE();`
	`1196`	`+ _PyEval_StartTheWorld(interp);`
`1196`	`1197`	`}`
`1197`	`1198`	`}`
`1198`	`1199`	`}`
`@@ -1381,9 +1382,10 @@ _Py_call_instrumentation_line(PyThreadState tstate, _PyInterpreterFrame frame,`
`1381`	`1382`	`}`
`1382`	`1383`	`else {`
`1383`	`1384`	`/* DISABLE */`
`1384`		`- LOCK_CODE(code);`
	`1385`	`+ PyInterpreterState *interp = tstate->interp;`
	`1386`	`+ _PyEval_StopTheWorld(interp);`
`1385`	`1387`	`remove_line_tools(code, i, 1 << tool);`
`1386`		`- UNLOCK_CODE();`
	`1388`	`+ _PyEval_StartTheWorld(interp);`
`1387`	`1389`	`}`
`1388`	`1390`	`} while (tools);`
`1389`	`1391`	`Py_DECREF(line_obj);`
`@@ -1438,9 +1440,10 @@ _Py_call_instrumentation_instruction(PyThreadState tstate, _PyInterpreterFrame`
`1438`	`1440`	`}`
`1439`	`1441`	`else {`
`1440`	`1442`	`/* DISABLE */`
`1441`		`- LOCK_CODE(code);`
	`1443`	`+ PyInterpreterState *interp = tstate->interp;`
	`1444`	`+ _PyEval_StopTheWorld(interp);`
`1442`	`1445`	`remove_per_instruction_tools(code, offset, 1 << tool);`
`1443`		`- UNLOCK_CODE();`
	`1446`	`+ _PyEval_StartTheWorld(interp);`
`1444`	`1447`	`}`
`1445`	`1448`	`}`
`1446`	`1449`	`Py_DECREF(offset_obj);`
`@@ -2995,9 +2998,10 @@ branch_handler_vectorcall(`
`2995`	`2998`	`// Orphaned NOT_TAKEN -- Jump removed by the compiler`
`2996`	`2999`	`return res;`
`2997`	`3000`	`}`
`2998`		`- LOCK_CODE(code);`
	`3001`	`+ PyInterpreterState *interp = _PyInterpreterState_GET();`
	`3002`	`+ _PyEval_StopTheWorld(interp);`
`2999`	`3003`	`remove_tools(code, offset, other_event, 1 << self->tool_id);`
`3000`		`- UNLOCK_CODE();`
	`3004`	`+ _PyEval_StartTheWorld(interp);`
`3001`	`3005`	`}`
`3002`	`3006`	`return res;`
`3003`	`3007`	`}`