python · maurycy · Jun 13, 2026 · Jun 13, 2026
diff --git a/Misc/NEWS.d/next/Library/2026-06-13-11-57-48.gh-issue-151436.UEDowO.rst b/Misc/NEWS.d/next/Library/2026-06-13-11-57-48.gh-issue-151436.UEDowO.rst
@@ -0,0 +1,4 @@
+Fix skewed stack trackes in the Tachyon profiler when caching is enabled and
+when generators and coroutines are profiled, by updating
+``tstate->last_profiled_frame`` at every frame-removal site. The issue resulted
+in total erasure of some callers. Patch by Maurycy Pawłowski-Wieroński.
diff --git a/Modules/_testinternalcapi/test_cases.c.h b/Modules/_testinternalcapi/test_cases.c.h
@@ -681,6 +681,9 @@ _gen_throw(PyGenObject *gen, int close_on_genexit,
                'yield from' or awaiting on with 'await'. */
             ret = _gen_throw((PyGenObject *)yf, close_on_genexit,
                              typ, val, tb);
+            if (tstate->last_profiled_frame == frame) {
+                tstate->last_profiled_frame = prev;
+            }
             tstate->current_frame = prev;
             frame->previous = NULL;
         }
@@ -701,6 +704,9 @@ _gen_throw(PyGenObject *gen, int close_on_genexit,
             frame->previous = prev;
             tstate->current_frame = frame;
             ret = PyObject_CallFunctionObjArgs(meth, typ, val, tb, NULL);
+            if (tstate->last_profiled_frame == frame) {
+                tstate->last_profiled_frame = prev;
+            }
             tstate->current_frame = prev;
             frame->previous = NULL;
             Py_DECREF(meth);

@@ -1860,6 +1860,9 @@ dummy_func(
             gen->gi_exc_state.previous_item = NULL;
             _Py_LeaveRecursiveCallPy(tstate);
             _PyInterpreterFrame *gen_frame = frame;
+            if (tstate->last_profiled_frame == gen_frame) {
+                tstate->last_profiled_frame = gen_frame->previous;
+            }
             frame = tstate->current_frame = frame->previous;
             gen_frame->previous = NULL;
             ((_PyThreadStateImpl *)tstate)->generator_return_kind = GENERATOR_YIELD;
@@ -5874,6 +5877,9 @@ dummy_func(
             gen_frame->owner = FRAME_OWNED_BY_GENERATOR;
             _Py_LeaveRecursiveCallPy(tstate);
             _PyInterpreterFrame *prev = frame->previous;
+            if (tstate->last_profiled_frame == frame) {
+                tstate->last_profiled_frame = prev;
+            }
             _PyThreadState_PopFrame(tstate, frame);
             frame = tstate->current_frame = prev;
             LOAD_IP(frame->return_offset);

@@ -2006,6 +2006,9 @@ _PyEvalFramePushAndInit(PyThreadState *tstate, _PyStackRef func,
     _PyFrame_Initialize(tstate, frame, func, locals, code, 0, previous);
     if (initialize_locals(tstate, func_obj, frame->localsplus, args, argcount, kwnames)) {
         assert(frame->owner == FRAME_OWNED_BY_THREAD);
+        if (tstate->last_profiled_frame == frame) {
+            tstate->last_profiled_frame = tstate->current_frame;
+        }
         clear_thread_frame(tstate, frame);
         return NULL;
     }

diff --git a/Python/executor_cases.c.h b/Python/executor_cases.c.h
diff --git a/Python/generated_cases.c.h b/Python/generated_cases.c.h