[Python-checkins] [3.6] bpo-30808: Use _Py_atomic API for concurrency-sensitive signal state (GH-2417) (#3007)
Antoine Pitrou
webhook-mailer at python.org
Sun Aug 6 13:32:42 EDT 2017
https://github.com/python/cpython/commit/57e836cb41656ac23042886db6b5985c036a7ce2
commit: 57e836cb41656ac23042886db6b5985c036a7ce2
branch: 3.6
author: Antoine Pitrou <pitrou at free.fr>
committer: GitHub <noreply at github.com>
date: 2017-08-06T19:32:39+02:00
summary:
[3.6] bpo-30808: Use _Py_atomic API for concurrency-sensitive signal state (GH-2417) (#3007)
* 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
(cherry picked from commit 2c8a5e4c968217f9672340e520942c4ed788d8de)
files:
A Misc/NEWS.d/next/Core and Builtins/2017-07-17-12-12-59.bpo-30808.bA3zOv.rst
M Modules/signalmodule.c
diff --git a/Misc/NEWS.d/next/Core and Builtins/2017-07-17-12-12-59.bpo-30808.bA3zOv.rst b/Misc/NEWS.d/next/Core and Builtins/2017-07-17-12-12-59.bpo-30808.bA3zOv.rst
new file mode 100644
index 00000000000..8adbbe7dc3a
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2017-07-17-12-12-59.bpo-30808.bA3zOv.rst
@@ -0,0 +1 @@
+Use _Py_atomic API for concurrency-sensitive signal state.
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index 30990f89c3e..0e6099fd361 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -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)
@@ -1264,11 +1266,11 @@ 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)
@@ -1492,7 +1494,7 @@ 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)
@@ -1513,7 +1515,7 @@ PyErr_CheckSignals(void)
int i;
PyObject *f;
- if (!is_tripped)
+ if (!_Py_atomic_load(&is_tripped))
return 0;
#ifdef WITH_THREAD
@@ -1535,16 +1537,16 @@ 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,
@@ -1552,7 +1554,7 @@ PyErr_CheckSignals(void)
Py_DECREF(arglist);
}
if (!result) {
- is_tripped = 1;
+ _Py_atomic_store(&is_tripped, 1);
return -1;
}
@@ -1591,12 +1593,12 @@ 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;
@@ -1606,11 +1608,11 @@ 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);
}
}
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