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Use the faulthandler module's infrastructure to write a GIL-less

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memory watchdog for timely stats collection.
This commit is contained in:
Antoine Pitrou 2011-10-04 11:51:23 +02:00
parent 031487eb3b
commit 75e78b6c77
2 changed files with 249 additions and 43 deletions
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183
Modules/faulthandler.c
View file

@ -13,6 +13,7 @@
#ifdef WITH_THREAD
# define FAULTHANDLER_LATER
# define FAULTHANDLER_WATCHDOG
#endif
#ifndef MS_WINDOWS
@ -65,6 +66,20 @@ static struct {
} thread;
#endif
#ifdef FAULTHANDLER_WATCHDOG
static struct {
int rfd;
int wfd;
PY_TIMEOUT_T period_us; /* period in microseconds */
/* The main thread always holds this lock. It is only released when
faulthandler_watchdog() is interrupted before this thread exits, or at
Python exit. */
PyThread_type_lock cancel_event;
/* released by child thread when joined */
PyThread_type_lock running;
} watchdog;
#endif
#ifdef FAULTHANDLER_USER
typedef struct {
int enabled;
@ -587,6 +602,138 @@ faulthandler_cancel_dump_tracebacks_later_py(PyObject *self)
}
#endif /* FAULTHANDLER_LATER */
#ifdef FAULTHANDLER_WATCHDOG
static void
file_watchdog(void *unused)
{
PyLockStatus st;
PY_TIMEOUT_T timeout;
const int MAXDATA = 1024;
char buf1[MAXDATA], buf2[MAXDATA];
char *data = buf1, *old_data = buf2;
Py_ssize_t data_len, old_data_len = -1;
#if defined(HAVE_PTHREAD_SIGMASK) && !defined(HAVE_BROKEN_PTHREAD_SIGMASK)
sigset_t set;
/* we don't want to receive any signal */
sigfillset(&set);
pthread_sigmask(SIG_SETMASK, &set, NULL);
#endif
/* On first pass, feed file contents immediately */
timeout = 0;
do {
st = PyThread_acquire_lock_timed(watchdog.cancel_event,
timeout, 0);
timeout = watchdog.period_us;
if (st == PY_LOCK_ACQUIRED) {
PyThread_release_lock(watchdog.cancel_event);
break;
}
/* Timeout => read and write data */
assert(st == PY_LOCK_FAILURE);
if (lseek(watchdog.rfd, 0, SEEK_SET) < 0) {
break;
}
data_len = read(watchdog.rfd, data, MAXDATA);
if (data_len < 0) {
break;
}
if (data_len != old_data_len || memcmp(data, old_data, data_len)) {
char *tdata;
Py_ssize_t tlen;
/* Contents changed, feed them to wfd */
long x = (long) data_len;
/* We can't do anything if the consumer is too slow, just bail out */
if (write(watchdog.wfd, (void *) &x, sizeof(x)) < sizeof(x))
break;
if (write(watchdog.wfd, data, data_len) < data_len)
break;
tdata = data;
data = old_data;
old_data = tdata;
tlen = data_len;
data_len = old_data_len;
old_data_len = tlen;
}
} while (1);
close(watchdog.rfd);
close(watchdog.wfd);
/* The only way out */
PyThread_release_lock(watchdog.running);
}
static void
cancel_file_watchdog(void)
{
/* Notify cancellation */
PyThread_release_lock(watchdog.cancel_event);
/* Wait for thread to join */
PyThread_acquire_lock(watchdog.running, 1);
PyThread_release_lock(watchdog.running);
/* The main thread should always hold the cancel_event lock */
PyThread_acquire_lock(watchdog.cancel_event, 1);
}
static PyObject*
faulthandler_file_watchdog(PyObject *self,
PyObject *args, PyObject *kwargs)
{
static char *kwlist[] = {"rfd", "wfd", "period", NULL};
double period;
PY_TIMEOUT_T period_us;
int rfd, wfd;
if (!PyArg_ParseTupleAndKeywords(args, kwargs,
"iid:_file_watchdog", kwlist,
&rfd, &wfd, &period))
return NULL;
if ((period * 1e6) >= (double) PY_TIMEOUT_MAX) {
PyErr_SetString(PyExc_OverflowError, "period value is too large");
return NULL;
}
period_us = (PY_TIMEOUT_T)(period * 1e6);
if (period_us <= 0) {
PyErr_SetString(PyExc_ValueError, "period must be greater than 0");
return NULL;
}
/* Cancel previous thread, if running */
cancel_file_watchdog();
watchdog.rfd = rfd;
watchdog.wfd = wfd;
watchdog.period_us = period_us;
/* Arm these locks to serve as events when released */
PyThread_acquire_lock(watchdog.running, 1);
if (PyThread_start_new_thread(file_watchdog, NULL) == -1) {
PyThread_release_lock(watchdog.running);
PyErr_SetString(PyExc_RuntimeError,
"unable to start file watchdog thread");
return NULL;
}
Py_RETURN_NONE;
}
static PyObject*
faulthandler_cancel_file_watchdog(PyObject *self)
{
cancel_file_watchdog();
Py_RETURN_NONE;
}
#endif /* FAULTHANDLER_WATCHDOG */
#ifdef FAULTHANDLER_USER
static int
faulthandler_register(int signum, int chain, _Py_sighandler_t *p_previous)
@ -973,6 +1120,18 @@ static PyMethodDef module_methods[] = {
"to dump_tracebacks_later().")},
#endif
#ifdef FAULTHANDLER_WATCHDOG
{"_file_watchdog",
(PyCFunction)faulthandler_file_watchdog, METH_VARARGS|METH_KEYWORDS,
PyDoc_STR("_file_watchdog(rfd, wfd, period):\n"
"feed the contents of 'rfd' to 'wfd', if changed,\n"
"every 'period seconds'.")},
{"_cancel_file_watchdog",
(PyCFunction)faulthandler_cancel_file_watchdog, METH_NOARGS,
PyDoc_STR("_cancel_file_watchdog():\ncancel the previous call "
"to _file_watchdog().")},
#endif
#ifdef FAULTHANDLER_USER
{"register",
(PyCFunction)faulthandler_register_py, METH_VARARGS|METH_KEYWORDS,
@ -1097,6 +1256,16 @@ int _PyFaulthandler_Init(void)
}
PyThread_acquire_lock(thread.cancel_event, 1);
#endif
#ifdef FAULTHANDLER_WATCHDOG
watchdog.cancel_event = PyThread_allocate_lock();
watchdog.running = PyThread_allocate_lock();
if (!watchdog.cancel_event || !watchdog.running) {
PyErr_SetString(PyExc_RuntimeError,
"could not allocate locks for faulthandler");
return -1;
}
PyThread_acquire_lock(watchdog.cancel_event, 1);
#endif
return faulthandler_env_options();
}
@ -1121,6 +1290,20 @@ void _PyFaulthandler_Fini(void)
}
#endif
#ifdef FAULTHANDLER_WATCHDOG
/* file watchdog */
cancel_file_watchdog();
if (watchdog.cancel_event) {
PyThread_release_lock(watchdog.cancel_event);
PyThread_free_lock(watchdog.cancel_event);
watchdog.cancel_event = NULL;
}
if (watchdog.running) {
PyThread_free_lock(watchdog.running);
watchdog.running = NULL;
}
#endif
#ifdef FAULTHANDLER_USER
/* user */
if (user_signals != NULL) {