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cpython/Modules/_multiprocessing/semaphore.c

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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"
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h> // gettimeofday()
#endif
#ifdef HAVE_MP_SEMAPHORE
// These match the values in Lib/multiprocessing/synchronize.py
enum { RECURSIVE_MUTEX, SEMAPHORE };
typedef struct {
PyObject_HEAD
SEM_HANDLE handle;
unsigned long last_tid;
int count;
int maxvalue;
int kind;
char *name;
} SemLockObject;
/*[python input]
class SEM_HANDLE_converter(CConverter):
type = "SEM_HANDLE"
format_unit = '"F_SEM_HANDLE"'
[python start generated code]*/
/*[python end generated code: output=da39a3ee5e6b4b0d input=3e0ad43e482d8716]*/
/*[clinic input]
module _multiprocessing
class _multiprocessing.SemLock "SemLockObject *" "&_PyMp_SemLockType"
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=935fb41b7d032599]*/
#include "clinic/semaphore.c.h"
#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;
}
}
/*[clinic input]
@critical_section
_multiprocessing.SemLock.acquire
block as blocking: bool = True
timeout as timeout_obj: object = None
Acquire the semaphore/lock.
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock_acquire_impl(SemLockObject *self, int blocking,
PyObject *timeout_obj)
/*[clinic end generated code: output=f9998f0b6b0b0872 input=079ca779975f3ad6]*/
{
double timeout;
DWORD res, full_msecs, nhandles;
HANDLE handles[2], sigint_event;
/* 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;
}
}
/*[clinic input]
@critical_section
_multiprocessing.SemLock.release
Release the semaphore/lock.
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock_release_impl(SemLockObject *self)
/*[clinic end generated code: output=b22f53ba96b0d1db input=9bd62d3645e7a531]*/
{
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 */
/*[clinic input]
@critical_section
_multiprocessing.SemLock.acquire
block as blocking: bool = True
timeout as timeout_obj: object = None
Acquire the semaphore/lock.
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock_acquire_impl(SemLockObject *self, int blocking,
PyObject *timeout_obj)
/*[clinic end generated code: output=f9998f0b6b0b0872 input=079ca779975f3ad6]*/
{
int res, err = 0;
struct timespec deadline = {0};
if (self->kind == RECURSIVE_MUTEX && ISMINE(self)) {
++self->count;
Py_RETURN_TRUE;
}
int use_deadline = (timeout_obj != Py_None);
if (use_deadline) {
double timeout = PyFloat_AsDouble(timeout_obj);
if (PyErr_Occurred()) {
return NULL;
}
if (timeout < 0.0) {
timeout = 0.0;
}
struct timeval now;
if (gettimeofday(&now, NULL) < 0) {
PyErr_SetFromErrno(PyExc_OSError);
return NULL;
}
long sec = (long) timeout;
long 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 (!use_deadline) {
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;
}
/*[clinic input]
@critical_section
_multiprocessing.SemLock.release
Release the semaphore/lock.
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock_release_impl(SemLockObject *self)
/*[clinic end generated code: output=b22f53ba96b0d1db input=9bd62d3645e7a531]*/
{
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 = (SemLockObject *)type->tp_alloc(type, 0);
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;
}
/*[clinic input]
@classmethod
_multiprocessing.SemLock.__new__
kind: int
value: int
maxvalue: int
name: str
unlink: bool
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock_impl(PyTypeObject *type, int kind, int value,
int maxvalue, const char *name, int unlink)
/*[clinic end generated code: output=30727e38f5f7577a input=fdaeb69814471c5b]*/
{
SEM_HANDLE handle = SEM_FAILED;
PyObject *result;
char *name_copy = 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 (!PyErr_Occurred()) {
_PyMp_SetError(NULL, MP_STANDARD_ERROR);
}
if (handle != SEM_FAILED)
SEM_CLOSE(handle);
PyMem_Free(name_copy);
return NULL;
}
/*[clinic input]
@classmethod
_multiprocessing.SemLock._rebuild
handle: SEM_HANDLE
kind: int
maxvalue: int
name: str(accept={str, NoneType})
/
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock__rebuild_impl(PyTypeObject *type, SEM_HANDLE handle,
int kind, int maxvalue,
const char *name)
/*[clinic end generated code: output=2aaee14f063f3bd9 input=f7040492ac6d9962]*/
{
char *name_copy = 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) {
PyErr_SetFromErrno(PyExc_OSError);
PyMem_Free(name_copy);
return NULL;
}
}
#endif
return newsemlockobject(type, handle, kind, maxvalue, name_copy);
}
static void
semlock_dealloc(SemLockObject* self)
{
PyTypeObject *tp = Py_TYPE(self);
PyObject_GC_UnTrack(self);
if (self->handle != SEM_FAILED)
SEM_CLOSE(self->handle);
PyMem_Free(self->name);
tp->tp_free(self);
Py_DECREF(tp);
}
/*[clinic input]
@critical_section
_multiprocessing.SemLock._count
Num of `acquire()`s minus num of `release()`s for this process.
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock__count_impl(SemLockObject *self)
/*[clinic end generated code: output=5ba8213900e517bb input=9fa6e0b321b16935]*/
{
return PyLong_FromLong((long)self->count);
}
/*[clinic input]
_multiprocessing.SemLock._is_mine
Whether the lock is owned by this thread.
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock__is_mine_impl(SemLockObject *self)
/*[clinic end generated code: output=92dc98863f4303be input=a96664cb2f0093ba]*/
{
/* only makes sense for a lock */
return PyBool_FromLong(ISMINE(self));
}
/*[clinic input]
_multiprocessing.SemLock._get_value
Get the value of the semaphore.
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock__get_value_impl(SemLockObject *self)
/*[clinic end generated code: output=64bc1b89bda05e36 input=cb10f9a769836203]*/
{
#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
}
/*[clinic input]
_multiprocessing.SemLock._is_zero
Return whether semaphore has value zero.
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock__is_zero_impl(SemLockObject *self)
/*[clinic end generated code: output=815d4c878c806ed7 input=294a446418d31347]*/
{
#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
}
/*[clinic input]
_multiprocessing.SemLock._after_fork
Rezero the net acquisition count after fork().
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock__after_fork_impl(SemLockObject *self)
/*[clinic end generated code: output=718bb27914c6a6c1 input=190991008a76621e]*/
{
self->count = 0;
Py_RETURN_NONE;
}
/*[clinic input]
@critical_section
_multiprocessing.SemLock.__enter__
Enter the semaphore/lock.
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock___enter___impl(SemLockObject *self)
/*[clinic end generated code: output=beeb2f07c858511f input=d35c9860992ee790]*/
{
return _multiprocessing_SemLock_acquire_impl(self, 1, Py_None);
}
/*[clinic input]
@critical_section
_multiprocessing.SemLock.__exit__
exc_type: object = None
exc_value: object = None
exc_tb: object = None
/
Exit the semaphore/lock.
[clinic start generated code]*/
static PyObject *
_multiprocessing_SemLock___exit___impl(SemLockObject *self,
PyObject *exc_type,
PyObject *exc_value, PyObject *exc_tb)
/*[clinic end generated code: output=3b37c1a9f8b91a03 input=1610c8cc3e0e337e]*/
{
return _multiprocessing_SemLock_release_impl(self);
}
static int
semlock_traverse(SemLockObject *s, visitproc visit, void *arg)
{
Py_VISIT(Py_TYPE(s));
return 0;
}
/*
* Semaphore methods
*/
static PyMethodDef semlock_methods[] = {
_MULTIPROCESSING_SEMLOCK_ACQUIRE_METHODDEF
_MULTIPROCESSING_SEMLOCK_RELEASE_METHODDEF
_MULTIPROCESSING_SEMLOCK___ENTER___METHODDEF
_MULTIPROCESSING_SEMLOCK___EXIT___METHODDEF
_MULTIPROCESSING_SEMLOCK__COUNT_METHODDEF
_MULTIPROCESSING_SEMLOCK__IS_MINE_METHODDEF
_MULTIPROCESSING_SEMLOCK__GET_VALUE_METHODDEF
_MULTIPROCESSING_SEMLOCK__IS_ZERO_METHODDEF
_MULTIPROCESSING_SEMLOCK__REBUILD_METHODDEF
_MULTIPROCESSING_SEMLOCK__AFTER_FORK_METHODDEF
{NULL}
};
/*
* Member table
*/
static PyMemberDef semlock_members[] = {
{"handle", T_SEM_HANDLE, offsetof(SemLockObject, handle), Py_READONLY,
""},
{"kind", Py_T_INT, offsetof(SemLockObject, kind), Py_READONLY,
""},
{"maxvalue", Py_T_INT, offsetof(SemLockObject, maxvalue), Py_READONLY,
""},
{"name", Py_T_STRING, offsetof(SemLockObject, name), Py_READONLY,
""},
{NULL}
};
/*
* Semaphore type
*/
static PyType_Slot _PyMp_SemLockType_slots[] = {
{Py_tp_dealloc, semlock_dealloc},
{Py_tp_getattro, PyObject_GenericGetAttr},
{Py_tp_setattro, PyObject_GenericSetAttr},
{Py_tp_methods, semlock_methods},
{Py_tp_members, semlock_members},
{Py_tp_alloc, PyType_GenericAlloc},
{Py_tp_new, _multiprocessing_SemLock},
{Py_tp_traverse, semlock_traverse},
{Py_tp_free, PyObject_GC_Del},
{Py_tp_doc, (void *)PyDoc_STR("Semaphore/Mutex type")},
{0, 0},
};
PyType_Spec _PyMp_SemLockType_spec = {
.name = "_multiprocessing.SemLock",
.basicsize = sizeof(SemLockObject),
.flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE),
.slots = _PyMp_SemLockType_slots,
};
/*
* Function to unlink semaphore names
*/
PyObject *
_PyMp_sem_unlink(const char *name)
{
if (SEM_UNLINK(name) < 0) {
_PyMp_SetError(NULL, MP_STANDARD_ERROR);
return NULL;
}
Py_RETURN_NONE;
}
#endif // HAVE_MP_SEMAPHORE
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