8000 gh-98257: Make _PyEval_SetTrace() reentrant by vstinner · Pull Request #98258 · python/cpython · GitHub
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gh-98257: Make _PyEval_SetTrace() reentrant #98258

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Merged
merged 2 commits into from
Oct 19, 2022
Merged

gh-98257: Make _PyEval_SetTrace() reentrant #98258

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62bca63
gh-98257: Make _PyEval_SetTrace() reentrant
vstinner Oct 14, 2022
0568430
Update test_sys_settrace and test_sys_setprofile
vstinner Oct 14, 2022
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gh-98257: Make _PyEval_SetTrace() reentrant 
Make sys.setprofile() and sys.settrace() functions reentrant.  They
can no long fail with: RuntimeError("Cannot install a trace function
while another trace function is being installed").

Make _PyEval_SetTrace() and _PyEval_SetProfile() functions reentrant,
rather than detecting and rejecting reentrant calls. Only delete the
reference to function arguments once the new function is fully set,
when a reentrant call is safe. Call also _PySys_Audit() earlier.
  • Loading branch information
@vstinner
vstinner committed Oct 14, 2022
commit 62bca632e2d97c6c87fd28530f8b7cd4863bdf60
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2022-10-14-12-29-05.gh-issue-98257.aMSMs2.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Make :func:`sys.setprofile` and :func:`sys.settrace` functions reentrant. They
can no long fail with: ``RuntimeError("Cannot install a trace function while
another trace function is being installed")``. Patch by Victor Stinner.
57 changes: 13 additions & 44 deletions Python/ceval.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6343,38 +6343,23 @@ _PyEval_SetProfile(PyThreadState *tstate, Py_tracefunc func, PyObject *arg)
/* The caller must hold the GIL */
assert(PyGILState_Check());

static int reentrant = 0;
if (reentrant) {
_PyErr_SetString(tstate, PyExc_RuntimeError, "Cannot install a profile function "
"while another profile function is being installed");
reentrant = 0;
return -1;
}
reentrant = 1;

/* Call _PySys_Audit() in the context of the current thread state,
even if tstate is not the current thread state. */
PyThreadState *current_tstate = _PyThreadState_GET();
if (_PySys_Audit(current_tstate, "sys.setprofile", NULL) < 0) {
reentrant = 0;
return -1;
}

PyObject *profileobj = tstate->c_profileobj;

tstate->c_profilefunc = NULL;
tstate->c_profileobj = NULL;
/* Must make sure that tracing is not ignored if 'profileobj' is freed */
_PyThreadState_UpdateTracingState(tstate);
Py_XDECREF(profileobj);

Py_XINCREF(arg);
tstate->c_profileobj = arg;
tstate->c_profilefunc = func;

PyObject *old_profileobj = tstate->c_profileobj;
tstate->c_profileobj = Py_XNewRef(arg);
/* Flag that tracing or profiling is turned on */
_PyThreadState_UpdateTracingState(tstate);
reentrant = 0;

// gh-98257: Only call Py_XDECREF() once the new profile function is fully
// set, so it's safe to call sys.setprofile() again (reentrant call).
Py_XDECREF(old_profileobj);

return 0;
}

Expand Down Expand Up @@ -6416,39 +6401,23 @@ _PyEval_SetTrace(PyThreadState *tstate, Py_tracefunc func, PyObject *arg)
/* The caller must hold the GIL */
assert(PyGILState_Check());

static int reentrant = 0;

if (reentrant) {
_PyErr_SetString(tstate, PyExc_RuntimeError, "Cannot install a trace function "
"while another trace function is being installed");
reentrant = 0;
return -1;
}
reentrant = 1;

/* Call _PySys_Audit() in the context of the current thread state,
even if tstate is not the current thread state. */
PyThreadState *current_tstate = _PyThreadState_GET();
if (_PySys_Audit(current_tstate, "sys.settrace", NULL) < 0) {
reentrant = 0;
return -1;
}

PyObject *traceobj = tstate->c_traceobj;

tstate->c_tracefunc = NULL;
tstate->c_traceobj = NULL;
/* Must make sure that profiling is not ignored if 'traceobj' is freed */
_PyThreadState_UpdateTracingState(tstate);
Py_XINCREF(arg);
Py_XDECREF(traceobj);
tstate->c_traceobj = arg;
tstate->c_tracefunc = func;

PyObject *old_traceobj = tstate->c_traceobj;
tstate->c_traceobj = Py_XNewRef(arg);
/* Flag that tracing or profiling is turned on */
_PyThreadState_UpdateTracingState(tstate);

reentrant = 0;
// gh-98257: Only call Py_XDECREF() once the new trace function is fully
// set, so it's safe to call sys.settrace() again (reentrant call).
Py_XDECREF(old_traceobj);

return 0;
}

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