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/*
* A type which wraps a semaphore
*
* semaphore.c
*
* Copyright (c) 2006-2008, R Oudkerk
* Licensed to PSF under a Contributor Agreement.
*/
#include "multiprocessing.h"
enum { RECURSIVE_MUTEX, SEMAPHORE };
typedef struct {
PyObject_HEAD
SEM_HANDLE handle;
unsigned long last_tid;
int count;
int maxvalue;
int kind;
char *name;
} SemLockObject;
#define ISMINE(o) (o->count > 0 && PyThread_get_thread_ident() == o->last_tid)
#ifdef MS_WINDOWS
/*
* Windows definitions
*/
#define SEM_FAILED NULL
#define SEM_CLEAR_ERROR() SetLastError(0)
#define SEM_GET_LAST_ERROR() GetLastError()
#define SEM_CREATE(name, val, max) CreateSemaphore(NULL, val, max, NULL)
#define SEM_CLOSE(sem) (CloseHandle(sem) ? 0 : -1)
#define SEM_GETVALUE(sem, pval) _GetSemaphoreValue(sem, pval)
#define SEM_UNLINK(name) 0
static int
_GetSemaphoreValue(HANDLE handle, long *value)
{
long previous;
switch (WaitForSingleObjectEx(handle, 0, FALSE)) {
case WAIT_OBJECT_0:
if (!ReleaseSemaphore(handle, 1, &previous))
return MP_STANDARD_ERROR;
*value = previous + 1;
return 0;
case WAIT_TIMEOUT:
*value = 0;
return 0;
default:
return MP_STANDARD_ERROR;
}
}
static PyObject *
semlock_acquire(SemLockObject *self, PyObject *args, PyObject *kwds)
{
int blocking = 1;
double timeout;
PyObject *timeout_obj = Py_None;
DWORD res, full_msecs, nhandles;
HANDLE handles[2], sigint_event;
static char *kwlist[] = {"block", "timeout", NULL};
if (!PyArg_ParseTupleAndKeywords(args, kwds, "|iO", kwlist,
&blocking, &timeout_obj))
return NULL;
/* calculate timeout */
if (!blocking) {
full_msecs = 0;
} else if (timeout_obj == Py_None) {
full_msecs = INFINITE;
} else {
timeout = PyFloat_AsDouble(timeout_obj);
if (PyErr_Occurred())
return NULL;
timeout *= 1000.0; /* convert to millisecs */
if (timeout < 0.0) {
timeout = 0.0;
} else if (timeout >= 0.5 * INFINITE) { /* 25 days */
PyErr_SetString(PyExc_OverflowError,
"timeout is too large");
return NULL;
}
full_msecs = (DWORD)(timeout + 0.5);
}
/* check whether we already own the lock */
if (self->kind == RECURSIVE_MUTEX && ISMINE(self)) {
++self->count;
Py_RETURN_TRUE;
}
/* check whether we can acquire without releasing the GIL and blocking */
if (WaitForSingleObjectEx(self->handle, 0, FALSE) == WAIT_OBJECT_0) {
self->last_tid = GetCurrentThreadId();
++self->count;
Py_RETURN_TRUE;
}
/* prepare list of handles */
nhandles = 0;
handles[nhandles++] = self->handle;
if (_PyOS_IsMainThread()) {
sigint_event = _PyOS_SigintEvent();
assert(sigint_event != NULL);
handles[nhandles++] = sigint_event;
}
else {
sigint_event = NULL;
}
/* do the wait */
Py_BEGIN_ALLOW_THREADS
if (sigint_event != NULL)
ResetEvent(sigint_event);
res = WaitForMultipleObjectsEx(nhandles, handles, FALSE, full_msecs, FALSE);
Py_END_ALLOW_THREADS
/* handle result */
switch (res) {
case WAIT_TIMEOUT:
Py_RETURN_FALSE;
case WAIT_OBJECT_0 + 0:
self->last_tid = GetCurrentThreadId();
++self->count;
Py_RETURN_TRUE;
case WAIT_OBJECT_0 + 1:
errno = EINTR;
return PyErr_SetFromErrno(PyExc_OSError);
case WAIT_FAILED:
return PyErr_SetFromWindowsErr(0);
default:
PyErr_Format(PyExc_RuntimeError, "WaitForSingleObject() or "
"WaitForMultipleObjects() gave unrecognized "
"value %u", res);
return NULL;
}
}
static PyObject *
semlock_release(SemLockObject *self, PyObject *args)
{
if (self->kind == RECURSIVE_MUTEX) {
if (!ISMINE(self)) {
PyErr_SetString(PyExc_AssertionError, "attempt to "
"release recursive lock not owned "
"by thread");
return NULL;
}
if (self->count > 1) {
--self->count;
Py_RETURN_NONE;
}
assert(self->count == 1);
}
if (!ReleaseSemaphore(self->handle, 1, NULL)) {
if (GetLastError() == ERROR_TOO_MANY_POSTS) {
PyErr_SetString(PyExc_ValueError, "semaphore or lock "
"released too many times");
return NULL;
} else {
return PyErr_SetFromWindowsErr(0);
}
}
--self->count;
Py_RETURN_NONE;
}
#else /* !MS_WINDOWS */
/*
* Unix definitions
*/
#define SEM_CLEAR_ERROR()
#define SEM_GET_LAST_ERROR() 0
#define SEM_CREATE(name, val, max) sem_open(name, O_CREAT | O_EXCL, 0600, val)
#define SEM_CLOSE(sem) sem_close(sem)
#define SEM_GETVALUE(sem, pval) sem_getvalue(sem, pval)
#define SEM_UNLINK(name) sem_unlink(name)
/* OS X 10.4 defines SEM_FAILED as -1 instead of (sem_t *)-1; this gives
compiler warnings, and (potentially) undefined behaviour. */
#ifdef __APPLE__
# undef SEM_FAILED
# define SEM_FAILED ((sem_t *)-1)
#endif
#ifndef HAVE_SEM_UNLINK
# define sem_unlink(name) 0
#endif
#ifndef HAVE_SEM_TIMEDWAIT
# define sem_timedwait(sem,deadline) sem_timedwait_save(sem,deadline,_save)
static int
sem_timedwait_save(sem_t *sem, struct timespec *deadline, PyThreadState *_save)
{
int res;
unsigned long delay, difference;
struct timeval now, tvdeadline, tvdelay;
errno = 0;
tvdeadline.tv_sec = deadline->tv_sec;
tvdeadline.tv_usec = deadline->tv_nsec / 1000;
for (delay = 0 ; ; delay += 1000) {
/* poll */
if (sem_trywait(sem) == 0)
return 0;
else if (errno != EAGAIN)
return MP_STANDARD_ERROR;
/* get current time */
if (gettimeofday(&now, NULL) < 0)
return MP_STANDARD_ERROR;
/* check for timeout */
if (tvdeadline.tv_sec < now.tv_sec ||
(tvdeadline.tv_sec == now.tv_sec &&
tvdeadline.tv_usec <= now.tv_usec)) {
errno = ETIMEDOUT;
return MP_STANDARD_ERROR;
}
/* calculate how much time is left */
difference = (tvdeadline.tv_sec - now.tv_sec) * 1000000 +
(tvdeadline.tv_usec - now.tv_usec);
/* check delay not too long -- maximum is 20 msecs */
if (delay > 20000)
delay = 20000;
if (delay > difference)
delay = difference;
/* sleep */
tvdelay.tv_sec = delay / 1000000;
tvdelay.tv_usec = delay % 1000000;
if (select(0, NULL, NULL, NULL, &tvdelay) < 0)
return MP_STANDARD_ERROR;
/* check for signals */
Py_BLOCK_THREADS
res = PyErr_CheckSignals();
Py_UNBLOCK_THREADS
if (res) {
errno = EINTR;
return MP_EXCEPTION_HAS_BEEN_SET;
}
}
}
#endif /* !HAVE_SEM_TIMEDWAIT */
static PyObject *
semlock_acquire(SemLockObject *self, PyObject *args, PyObject *kwds)
{
int blocking = 1, res, err = 0;
double timeout;
PyObject *timeout_obj = Py_None;
struct timespec deadline = {0};
struct timeval now;
long sec, nsec;
static char *kwlist[] = {"block", "timeout", NULL};
if (!PyArg_ParseTupleAndKeywords(args, kwds, "|iO", kwlist,
&blocking, &timeout_obj))
return NULL;
if (self->kind == RECURSIVE_MUTEX && ISMINE(self)) {
++self->count;
Py_RETURN_TRUE;
}
if (timeout_obj != Py_None) {
timeout = PyFloat_AsDouble(timeout_obj);
if (PyErr_Occurred())
return NULL;
if (timeout < 0.0)
timeout = 0.0;
if (gettimeofday(&now, NULL) < 0) {
PyErr_SetFromErrno(PyExc_OSError);
return NULL;
}
sec = (long) timeout;
nsec = (long) (1e9 * (timeout - sec) + 0.5);
deadline.tv_sec = now.tv_sec + sec;
deadline.tv_nsec = now.tv_usec * 1000 + nsec;
deadline.tv_sec += (deadline.tv_nsec / 1000000000);
deadline.tv_nsec %= 1000000000;
}
/* Check whether we can acquire without releasing the GIL and blocking */
do {
res = sem_trywait(self->handle);
err = errno;
} while (res < 0 && errno == EINTR && !PyErr_CheckSignals());
errno = err;
if (res < 0 && errno == EAGAIN && blocking) {
/* Couldn't acquire immediately, need to block */
do {
Py_BEGIN_ALLOW_THREADS
if (timeout_obj == Py_None) {
res = sem_wait(self->handle);
}
else {
res = sem_timedwait(self->handle, &deadline);
}
Py_END_ALLOW_THREADS
err = errno;
if (res == MP_EXCEPTION_HAS_BEEN_SET)
break;
} while (res < 0 && errno == EINTR && !PyErr_CheckSignals());
}
if (res < 0) {
errno = err;
if (errno == EAGAIN || errno == ETIMEDOUT)
Py_RETURN_FALSE;
else if (errno == EINTR)
return NULL;
else
return PyErr_SetFromErrno(PyExc_OSError);
}
++self->count;
self->last_tid = PyThread_get_thread_ident();
Py_RETURN_TRUE;
}
static PyObject *
semlock_release(SemLockObject *self, PyObject *args)
{
if (self->kind == RECURSIVE_MUTEX) {
if (!ISMINE(self)) {
PyErr_SetString(PyExc_AssertionError, "attempt to "
"release recursive lock not owned "
"by thread");
return NULL;
}
if (self->count > 1) {
--self->count;
Py_RETURN_NONE;
}
assert(self->count == 1);
} else {
#ifdef HAVE_BROKEN_SEM_GETVALUE
/* We will only check properly the maxvalue == 1 case */
if (self->maxvalue == 1) {
/* make sure that already locked */
if (sem_trywait(self->handle) < 0) {
if (errno != EAGAIN) {
PyErr_SetFromErrno(PyExc_OSError);
return NULL;
}
/* it is already locked as expected */
} else {
/* it was not locked so undo wait and raise */
if (sem_post(self->handle) < 0) {
PyErr_SetFromErrno(PyExc_OSError);
return NULL;
}
PyErr_SetString(PyExc_ValueError, "semaphore "
"or lock released too many "
"times");
return NULL;
}
}
#else
int sval;
/* This check is not an absolute guarantee that the semaphore
does not rise above maxvalue. */
if (sem_getvalue(self->handle, &sval) < 0) {
return PyErr_SetFromErrno(PyExc_OSError);
} else if (sval >= self->maxvalue) {
PyErr_SetString(PyExc_ValueError, "semaphore or lock "
"released too many times");
return NULL;
}
#endif
}
if (sem_post(self->handle) < 0)
return PyErr_SetFromErrno(PyExc_OSError);
--self->count;
Py_RETURN_NONE;
}
#endif /* !MS_WINDOWS */
/*
* All platforms
*/
static PyObject *
newsemlockobject(PyTypeObject *type, SEM_HANDLE handle, int kind, int maxvalue,
char *name)
{
SemLockObject *self;
self = PyObject_New(SemLockObject, type);
if (!self)
return NULL;
self->handle = handle;
self->kind = kind;
self->count = 0;
self->last_tid = 0;
self->maxvalue = maxvalue;
self->name = name;
return (PyObject*)self;
}
static PyObject *
semlock_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
SEM_HANDLE handle = SEM_FAILED;
int kind, maxvalue, value, unlink;
PyObject *result;
char *name, *name_copy = NULL;
static char *kwlist[] = {"kind", "value", "maxvalue", "name", "unlink",
NULL};
if (!PyArg_ParseTupleAndKeywords(args, kwds, "iiisi", kwlist,
&kind, &value, &maxvalue, &name, &unlink))
return NULL;
if (kind != RECURSIVE_MUTEX && kind != SEMAPHORE) {
PyErr_SetString(PyExc_ValueError, "unrecognized kind");
return NULL;
}
if (!unlink) {
name_copy = PyMem_Malloc(strlen(name) + 1);
if (name_copy == NULL) {
return PyErr_NoMemory();
}
strcpy(name_copy, name);
}
SEM_CLEAR_ERROR();
handle = SEM_CREATE(name, value, maxvalue);
/* On Windows we should fail if GetLastError()==ERROR_ALREADY_EXISTS */
if (handle == SEM_FAILED || SEM_GET_LAST_ERROR() != 0)
goto failure;
if (unlink && SEM_UNLINK(name) < 0)
goto failure;
result = newsemlockobject(type, handle, kind, maxvalue, name_copy);
if (!result)
goto failure;
return result;
failure:
if (handle != SEM_FAILED)
SEM_CLOSE(handle);
PyMem_Free(name_copy);
if (!PyErr_Occurred()) {
_PyMp_SetError(NULL, MP_STANDARD_ERROR);
}
return NULL;
}
static PyObject *
semlock_rebuild(PyTypeObject *type, PyObject *args)
{
SEM_HANDLE handle;
int kind, maxvalue;
char *name, *name_copy = NULL;
if (!PyArg_ParseTuple(args, F_SEM_HANDLE "iiz",
&handle, &kind, &maxvalue, &name))
return NULL;
if (name != NULL) {
name_copy = PyMem_Malloc(strlen(name) + 1);
if (name_copy == NULL)
return PyErr_NoMemory();
strcpy(name_copy, name);
}
#ifndef MS_WINDOWS
if (name != NULL) {
handle = sem_open(name, 0);
if (handle == SEM_FAILED) {
PyMem_Free(name_copy);
return PyErr_SetFromErrno(PyExc_OSError);
}
}
#endif
return newsemlockobject(type, handle, kind, maxvalue, name_copy);
}
static void
semlock_dealloc(SemLockObject* self)
{
if (self->handle != SEM_FAILED)
SEM_CLOSE(self->handle);
PyMem_Free(self->name);
PyObject_Del(self);
}
static PyObject *
semlock_count(SemLockObject *self, PyObject *Py_UNUSED(ignored))
{
return PyLong_FromLong((long)self->count);
}
static PyObject *
semlock_ismine(SemLockObject *self, PyObject *Py_UNUSED(ignored))
{
/* only makes sense for a lock */
return PyBool_FromLong(ISMINE(self));
}
static PyObject *
semlock_getvalue(SemLockObject *self, PyObject *Py_UNUSED(ignored))
{
#ifdef HAVE_BROKEN_SEM_GETVALUE
PyErr_SetNone(PyExc_NotImplementedError);
return NULL;
#else
int sval;
if (SEM_GETVALUE(self->handle, &sval) < 0)
return _PyMp_SetError(NULL, MP_STANDARD_ERROR);
/* some posix implementations use negative numbers to indicate
the number of waiting threads */
if (sval < 0)
sval = 0;
return PyLong_FromLong((long)sval);
#endif
}
static PyObject *
semlock_iszero(SemLockObject *self, PyObject *Py_UNUSED(ignored))
{
#ifdef HAVE_BROKEN_SEM_GETVALUE
if (sem_trywait(self->handle) < 0) {
if (errno == EAGAIN)
Py_RETURN_TRUE;
return _PyMp_SetError(NULL, MP_STANDARD_ERROR);
} else {
if (sem_post(self->handle) < 0)
return _PyMp_SetError(NULL, MP_STANDARD_ERROR);
Py_RETURN_FALSE;
}
#else
int sval;
if (SEM_GETVALUE(self->handle, &sval) < 0)
return _PyMp_SetError(NULL, MP_STANDARD_ERROR);
return PyBool_FromLong((long)sval == 0);
#endif
}
static PyObject *
semlock_afterfork(SemLockObject *self, PyObject *Py_UNUSED(ignored))
{
self->count = 0;
Py_RETURN_NONE;
}
/*
* Semaphore methods
*/
static PyMethodDef semlock_methods[] = {
{"acquire", (PyCFunction)(void(*)(void))semlock_acquire, METH_VARARGS | METH_KEYWORDS,
"acquire the semaphore/lock"},
{"release", (PyCFunction)semlock_release, METH_NOARGS,
"release the semaphore/lock"},
{"__enter__", (PyCFunction)(void(*)(void))semlock_acquire, METH_VARARGS | METH_KEYWORDS,
"enter the semaphore/lock"},
{"__exit__", (PyCFunction)semlock_release, METH_VARARGS,
"exit the semaphore/lock"},
{"_count", (PyCFunction)semlock_count, METH_NOARGS,
"num of `acquire()`s minus num of `release()`s for this process"},
{"_is_mine", (PyCFunction)semlock_ismine, METH_NOARGS,
"whether the lock is owned by this thread"},
{"_get_value", (PyCFunction)semlock_getvalue, METH_NOARGS,
"get the value of the semaphore"},
{"_is_zero", (PyCFunction)semlock_iszero, METH_NOARGS,
"returns whether semaphore has value zero"},
{"_rebuild", (PyCFunction)semlock_rebuild, METH_VARARGS | METH_CLASS,
""},
{"_after_fork", (PyCFunction)semlock_afterfork, METH_NOARGS,
"rezero the net acquisition count after fork()"},
{NULL}
};
/*
* Member table
*/
static PyMemberDef semlock_members[] = {
{"handle", T_SEM_HANDLE, offsetof(SemLockObject, handle), READONLY,
""},
{"kind", T_INT, offsetof(SemLockObject, kind), READONLY,
""},
{"maxvalue", T_INT, offsetof(SemLockObject, maxvalue), READONLY,
""},
{"name", T_STRING, offsetof(SemLockObject, name), READONLY,
""},
{NULL}
};
/*
* Semaphore type
*/
PyTypeObject _PyMp_SemLockType = {
PyVarObject_HEAD_INIT(NULL, 0)
/* tp_name */ "_multiprocessing.SemLock",
/* tp_basicsize */ sizeof(SemLockObject),
/* tp_itemsize */ 0,
/* tp_dealloc */ (destructor)semlock_dealloc,
/* tp_vectorcall_offset */ 0,
/* tp_getattr */ 0,
/* tp_setattr */ 0,
/* tp_as_async */ 0,
/* tp_repr */ 0,
/* tp_as_number */ 0,
/* tp_as_sequence */ 0,
/* tp_as_mapping */ 0,
/* tp_hash */ 0,
/* tp_call */ 0,
/* tp_str */ 0,
/* tp_getattro */ 0,
/* tp_setattro */ 0,
/* tp_as_buffer */ 0,
/* tp_flags */ Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
/* tp_doc */ "Semaphore/Mutex type",
/* tp_traverse */ 0,
/* tp_clear */ 0,
/* tp_richcompare */ 0,
/* tp_weaklistoffset */ 0,
/* tp_iter */ 0,
/* tp_iternext */ 0,
/* tp_methods */ semlock_methods,
/* tp_members */ semlock_members,
/* tp_getset */ 0,
/* tp_base */ 0,
/* tp_dict */ 0,
/* tp_descr_get */ 0,
/* tp_descr_set */ 0,
/* tp_dictoffset */ 0,
/* tp_init */ 0,
/* tp_alloc */ 0,
/* tp_new */ semlock_new,
};
/*
* Function to unlink semaphore names
*/
PyObject *
_PyMp_sem_unlink(PyObject *ignore, PyObject *args)
{
char *name;
if (!PyArg_ParseTuple(args, "s", &name))
return NULL;
if (SEM_UNLINK(name) < 0) {
_PyMp_SetError(NULL, MP_STANDARD_ERROR);
return NULL;
}
Py_RETURN_NONE;
}
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