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bpo-30808: Use _Py_atomic API for concurrency-sensitive signal state (#2417)

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* Improve signal delivery

Avoid using Py_AddPendingCall from signal handler, to avoid calling signal-unsafe functions.

* Remove unused function

* Improve comments

* Use _Py_atomic API for concurrency-sensitive signal state

* Add blurb
This commit is contained in:
Antoine Pitrou 2017-07-17 12:25:19 +02:00 committed by GitHub
parent 68d663cf85
commit 2c8a5e4c96
2 changed files with 21 additions and 18 deletions
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1
Misc/NEWS.d/next/Core and Builtins/2017-07-17-12-12-59.bpo-30808.bA3zOv.rst Normal file
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@ -0,0 +1 @@
Use _Py_atomic API for concurrency-sensitive signal state.

38
Modules/signalmodule.c
View file

@ -93,7 +93,7 @@ static pid_t main_pid;
#endif
static volatile struct {
sig_atomic_t tripped;
_Py_atomic_int tripped;
PyObject *func;
} Handlers[NSIG];
@ -113,7 +113,7 @@ static volatile sig_atomic_t wakeup_fd = -1;
#endif
/* Speed up sigcheck() when none tripped */
static volatile sig_atomic_t is_tripped = 0;
static _Py_atomic_int is_tripped;
static PyObject *DefaultHandler;
static PyObject *IgnoreHandler;
@ -240,11 +240,13 @@ trip_signal(int sig_num)
int fd;
Py_ssize_t rc;
Handlers[sig_num].tripped = 1;
_Py_atomic_store_relaxed(&Handlers[sig_num].tripped, 1);
/* Set is_tripped after setting .tripped, as it gets
cleared in PyErr_CheckSignals() before .tripped. */
is_tripped = 1;
_Py_atomic_store(&is_tripped, 1);
/* Notify ceval.c */
_PyEval_SignalReceived();
/* And then write to the wakeup fd *after* setting all the globals and
@ -465,7 +467,7 @@ signal_signal_impl(PyObject *module, int signalnum, PyObject *handler)
return NULL;
}
old_handler = Handlers[signalnum].func;
Handlers[signalnum].tripped = 0;
_Py_atomic_store_relaxed(&Handlers[signalnum].tripped, 0);
Py_INCREF(handler);
Handlers[signalnum].func = handler;
if (old_handler != NULL)
@ -1269,11 +1271,11 @@ PyInit__signal(void)
goto finally;
Py_INCREF(IntHandler);
Handlers[0].tripped = 0;
_Py_atomic_store_relaxed(&Handlers[0].tripped, 0);
for (i = 1; i < NSIG; i++) {
void (*t)(int);
t = PyOS_getsig(i);
Handlers[i].tripped = 0;
_Py_atomic_store_relaxed(&Handlers[i].tripped, 0);
if (t == SIG_DFL)
Handlers[i].func = DefaultHandler;
else if (t == SIG_IGN)
@ -1497,7 +1499,7 @@ finisignal(void)
for (i = 1; i < NSIG; i++) {
func = Handlers[i].func;
Handlers[i].tripped = 0;
_Py_atomic_store_relaxed(&Handlers[i].tripped, 0);
Handlers[i].func = NULL;
if (i != SIGINT && func != NULL && func != Py_None &&
func != DefaultHandler && func != IgnoreHandler)
@ -1518,7 +1520,7 @@ PyErr_CheckSignals(void)
int i;
PyObject *f;
if (!is_tripped)
if (!_Py_atomic_load(&is_tripped))
return 0;
#ifdef WITH_THREAD
@ -1540,16 +1542,16 @@ PyErr_CheckSignals(void)
* we receive a signal i after we zero is_tripped and before we
* check Handlers[i].tripped.
*/
is_tripped = 0;
_Py_atomic_store(&is_tripped, 0);
if (!(f = (PyObject *)PyEval_GetFrame()))
f = Py_None;
for (i = 1; i < NSIG; i++) {
if (Handlers[i].tripped) {
if (_Py_atomic_load_relaxed(&Handlers[i].tripped)) {
PyObject *result = NULL;
PyObject *arglist = Py_BuildValue("(iO)", i, f);
Handlers[i].tripped = 0;
_Py_atomic_store_relaxed(&Handlers[i].tripped, 0);
if (arglist) {
result = PyEval_CallObject(Handlers[i].func,
@ -1557,7 +1559,7 @@ PyErr_CheckSignals(void)
Py_DECREF(arglist);
}
if (!result) {
is_tripped = 1;
_Py_atomic_store(&is_tripped, 1);
return -1;
}
@ -1596,12 +1598,12 @@ PyOS_FiniInterrupts(void)
int
PyOS_InterruptOccurred(void)
{
if (Handlers[SIGINT].tripped) {
if (_Py_atomic_load_relaxed(&Handlers[SIGINT].tripped)) {
#ifdef WITH_THREAD
if (PyThread_get_thread_ident() != main_thread)
return 0;
#endif
Handlers[SIGINT].tripped = 0;
_Py_atomic_store_relaxed(&Handlers[SIGINT].tripped, 0);
return 1;
}
return 0;
@ -1611,11 +1613,11 @@ static void
_clear_pending_signals(void)
{
int i;
if (!is_tripped)
if (!_Py_atomic_load(&is_tripped))
return;
is_tripped = 0;
_Py_atomic_store(&is_tripped, 0);
for (i = 1; i < NSIG; ++i) {
Handlers[i].tripped = 0;
_Py_atomic_store_relaxed(&Handlers[i].tripped, 0);
}
}