pythongh-144763: Don't detach the GIL in tracemalloc (python#144779)

tracemalloc no longer detaches the GIL to acquire its internal lock.

Co-authored-by: Kumar Aditya <kumaraditya@python.org>
(cherry picked from commit 83f4fff)

Author: vstinner

Misc/NEWS.d/next/Library/2026-02-13-11-14-18.gh-issue-144763.cDwnEE.rst

@@ -0,0 +1,2 @@
+Fix a race condition in :mod:`tracemalloc`: it no longer detaches the attached
+thread state to acquire its internal lock. Patch by Victor Stinner.

Python/tracemalloc.c

@@ -224,13 +224,20 @@ tracemalloc_get_frame(_PyInterpreterFrame *pyframe, frame_t *frame)
     assert(PyStackRef_CodeCheck(pyframe->f_executable));
     frame->filename = &_Py_STR(anon_unknown);
 
-    int lineno = PyUnstable_InterpreterFrame_GetLine(pyframe);
+    int lineno = -1;
+    PyCodeObject *code = _PyFrame_GetCode(pyframe);
+    // PyUnstable_InterpreterFrame_GetLine() cannot but used, since it uses
+    // a critical section which can trigger a deadlock.
+    int lasti = _PyFrame_SafeGetLasti(pyframe);
+    if (lasti >= 0) {
+        lineno = _PyCode_SafeAddr2Line(code, lasti);
+    }
     if (lineno < 0) {
         lineno = 0;
     }
     frame->lineno = (unsigned int)lineno;
 
-    PyObject *filename = filename = _PyFrame_GetCode(pyframe)->co_filename;
+    PyObject *filename = code->co_filename;
     if (filename == NULL) {
 #ifdef TRACE_DEBUG
         tracemalloc_error("failed to get the filename of the code object");
@@ -853,7 +860,8 @@ _PyTraceMalloc_Stop(void)
     TABLES_LOCK();
 
     if (!tracemalloc_config.tracing) {
-        goto done;
+        TABLES_UNLOCK();
+        return;
     }
 
     /* stop tracing Python memory allocations */
@@ -870,10 +878,12 @@ _PyTraceMalloc_Stop(void)
     raw_free(tracemalloc_traceback);
     tracemalloc_traceback = NULL;
 
-    (void)PyRefTracer_SetTracer(NULL, NULL);
-
-done:
     TABLES_UNLOCK();
+
+    // Call it after TABLES_UNLOCK() since it calls _PyEval_StopTheWorldAll()
+    // which would lead to a deadlock with TABLES_LOCK() which doesn't detach
+    // the thread state.
+    (void)PyRefTracer_SetTracer(NULL, NULL);
 }