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bpo-35724: Explicitly require the main interpreter for signal-handling. #11530

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Merged
ericsnowcurrently merged 5 commits into from
Feb 23, 2019
Merged

bpo-35724: Explicitly require the main interpreter for signal-handling. #11530

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e9810a7
Factor out _PyErr_CheckSignals().
ericsnowcurrently Jan 11, 2019
a1c89ac
Factor out is_main().
ericsnowcurrently Jan 11, 2019
c21d282
Also check if is main interpreter.
ericsnowcurrently Jan 11, 2019
f18e34d
Add a NEWS entry.
ericsnowcurrently Jan 11, 2019
c5742f2
Make a function static.
ericsnowcurrently Feb 23, 2019
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1 change: 1 addition & 0 deletions Include/cpython/pyerrors.h
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Original file line number Diff line number Diff line change
Expand Up @@ -133,6 +133,7 @@ PyAPI_FUNC(PyObject *) _PyErr_TrySetFromCause(
/* In signalmodule.c */

int PySignal_SetWakeupFd(int fd);
PyAPI_FUNC(int) _PyErr_CheckSignals(void);

/* Support for adding program text to SyntaxErrors */

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2019-01-11-14-46-08.bpo-35724.Wv79MG.rst
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@@ -0,0 +1,2 @@
Signal-handling is now guaranteed to happen relative to the main
interpreter.
36 changes: 28 additions & 8 deletions Modules/signalmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -99,6 +99,7 @@ class sigset_t_converter(CConverter):
#include "pythread.h"
static unsigned long main_thread;
static pid_t main_pid;
static PyInterpreterState *main_interp;

static volatile struct {
_Py_atomic_int tripped;
Expand Down Expand Up @@ -185,6 +186,13 @@ itimer_retval(struct itimerval *iv)
}
#endif

static int
is_main(void)
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{
return PyThread_get_thread_ident() == main_thread &&
_PyInterpreterState_Get() == main_interp;
}

static PyObject *
signal_default_int_handler(PyObject *self, PyObject *args)
{
Expand Down Expand Up @@ -464,7 +472,7 @@ signal_signal_impl(PyObject *module, int signalnum, PyObject *handler)
return NULL;
}
#endif
if (PyThread_get_thread_ident() != main_thread) {
if (!is_main()) {
PyErr_SetString(PyExc_ValueError,
"signal only works in main thread");
return NULL;
Expand All @@ -486,7 +494,7 @@ signal_signal_impl(PyObject *module, int signalnum, PyObject *handler)
else
func = signal_handler;
/* Check for pending signals before changing signal handler */
if (PyErr_CheckSignals()) {
if (_PyErr_CheckSignals()) {
return NULL;
}
if (PyOS_setsig(signalnum, func) == SIG_ERR) {
Expand Down Expand Up @@ -681,7 +689,7 @@ signal_set_wakeup_fd(PyObject *self, PyObject *args, PyObject *kwds)
return NULL;
#endif

if (PyThread_get_thread_ident() != main_thread) {
if (!is_main()) {
PyErr_SetString(PyExc_ValueError,
"set_wakeup_fd only works in main thread");
return NULL;
Expand Down Expand Up @@ -1314,6 +1322,7 @@ PyInit__signal(void)

main_thread = PyThread_get_thread_ident();
main_pid = getpid();
main_interp = _PyInterpreterState_Get();

/* Create the module and add the functions */
m = PyModule_Create(&signalmodule);
Expand Down Expand Up @@ -1606,16 +1615,25 @@ finisignal(void)
/* Declared in pyerrors.h */
int
PyErr_CheckSignals(void)
{
if (!is_main()) {
return 0;
}

return _PyErr_CheckSignals();
}


/* Declared in cpython/pyerrors.h */
int
_PyErr_CheckSignals(void)
{
int i;
PyObject *f;

if (!_Py_atomic_load(&is_tripped))
return 0;

if (PyThread_get_thread_ident() != main_thread)
return 0;

/*
* The is_tripped variable is meant to speed up the calls to
* PyErr_CheckSignals (both directly or via pending calls) when no
Expand Down Expand Up @@ -1687,8 +1705,9 @@ int
PyOS_InterruptOccurred(void)
{
if (_Py_atomic_load_relaxed(&Handlers[SIGINT].tripped)) {
if (PyThread_get_thread_ident() != main_thread)
if (!is_main()) {
return 0;
}
_Py_atomic_store_relaxed(&Handlers[SIGINT].tripped, 0);
return 1;
}
Expand Down Expand Up @@ -1716,12 +1735,13 @@ _PySignal_AfterFork(void)
_clear_pending_signals();
main_thread = PyThread_get_thread_ident();
main_pid = getpid();
main_interp = _PyInterpreterState_Get();
}

int
_PyOS_IsMainThread(void)
{
return PyThread_get_thread_ident() == main_thread;
return is_main();
}

#ifdef MS_WINDOWS
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9 changes: 8 additions & 1 deletion Python/ceval.c
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Expand Up @@ -379,9 +379,16 @@ handle_signals(void)
{
return 0;
}
/*
* Ensure that the thread isn't currently running some other
* interpreter.
*/
if (_PyInterpreterState_GET_UNSAFE() != _PyRuntime.interpreters.main) {
return 0;
}

UNSIGNAL_PENDING_SIGNALS();
if (PyErr_CheckSignals() < 0) {
if (_PyErr_CheckSignals() < 0) {
SIGNAL_PENDING_SIGNALS(); /* We're not done yet */
return -1;
}
Expand Down