gh-114940: Use fine-grained mutex protection for PyInterpreterState.threads

Include/internal/pycore_interp.h

@@ -139,6 +139,8 @@ struct _is {
            or the size specified by the THREAD_STACK_SIZE macro. */
         /* Used in Python/thread.c. */
         size_t stacksize;
+        /* The mutex lock of the current executing thread. */
+        PyMutex mutex;
     } threads;
 
     /* Reference to the _PyRuntime global variable. This field exists

Include/internal/pycore_pystate.h

@@ -263,6 +263,11 @@ extern int _PyOS_InterruptOccurred(PyThreadState *tstate);
 #define HEAD_UNLOCK(runtime) \
     PyMutex_Unlock(&(runtime)->interpreters.mutex)
 
+#define INTERP_THREAD_LOCK(interpstate) \
+    PyMutex_LockFlags(&(interpstate)->threads.mutex, _Py_LOCK_DONT_DETACH)
+#define INTERP_THREAD_UNLOCK(interpstate) \
+    PyMutex_Unlock(&(interpstate)->threads.mutex)
+
 // Get the configuration of the current interpreter.
 // The caller must hold the GIL.
 // Export for test_peg_generator.

Python/ceval.c

@@ -2341,20 +2341,19 @@ void
 PyEval_SetProfileAllThreads(Py_tracefunc func, PyObject *arg)
 {
     PyThreadState *this_tstate = _PyThreadState_GET();
-    PyInterpreterState* interp = this_tstate->interp;
+    PyInterpreterState *interp = this_tstate->interp;
 
-    _PyRuntimeState *runtime = &_PyRuntime;
-    HEAD_LOCK(runtime);
+    INTERP_THREAD_LOCK(interp);
     PyThreadState* ts = PyInterpreterState_ThreadHead(interp);
-    HEAD_UNLOCK(runtime);
+    INTERP_THREAD_UNLOCK(interp);
 
     while (ts) {
         if (_PyEval_SetProfile(ts, func, arg) < 0) {
             PyErr_FormatUnraisable("Exception ignored in PyEval_SetProfileAllThreads");
         }
-        HEAD_LOCK(runtime);
+        INTERP_THREAD_LOCK(interp);
         ts = PyThreadState_Next(ts);
-        HEAD_UNLOCK(runtime);
+        INTERP_THREAD_UNLOCK(interp);
     }
 }
 
@@ -2372,20 +2371,19 @@ void
 PyEval_SetTraceAllThreads(Py_tracefunc func, PyObject *arg)
 {
     PyThreadState *this_tstate = _PyThreadState_GET();
-    PyInterpreterState* interp = this_tstate->interp;
+    PyInterpreterState *interp = this_tstate->interp;
 
-    _PyRuntimeState *runtime = &_PyRuntime;
-    HEAD_LOCK(runtime);
+    INTERP_THREAD_LOCK(interp);
     PyThreadState* ts = PyInterpreterState_ThreadHead(interp);
-    HEAD_UNLOCK(runtime);
+    INTERP_THREAD_UNLOCK(interp);
 
     while (ts) {
         if (_PyEval_SetTrace(ts, func, arg) < 0) {
             PyErr_FormatUnraisable("Exception ignored in PyEval_SetTraceAllThreads");
         }
-        HEAD_LOCK(runtime);
+        INTERP_THREAD_LOCK(interp);
         ts = PyThreadState_Next(ts);
-        HEAD_UNLOCK(runtime);
+        INTERP_THREAD_UNLOCK(interp);
     }
 }