cpython/Python/pystate.c

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/* Thread and interpreter state structures and their interfaces */
#include "Python.h"
#ifdef HAVE_DLOPEN
#ifdef HAVE_DLFCN_H
#include <dlfcn.h>
#endif
#ifndef RTLD_LAZY
#define RTLD_LAZY 1
#endif
#endif
#define ZAP(x) { \
PyObject *tmp = (PyObject *)(x); \
(x) = NULL; \
Py_XDECREF(tmp); \
}
#ifdef WITH_THREAD
#include "pythread.h"
static PyThread_type_lock head_mutex = NULL; /* Protects interp->tstate_head */
#define HEAD_INIT() (void)(head_mutex || (head_mutex = PyThread_allocate_lock()))
#define HEAD_LOCK() PyThread_acquire_lock(head_mutex, WAIT_LOCK)
#define HEAD_UNLOCK() PyThread_release_lock(head_mutex)
#else
#define HEAD_INIT() /* Nothing */
#define HEAD_LOCK() /* Nothing */
#define HEAD_UNLOCK() /* Nothing */
#endif
static PyInterpreterState *interp_head = NULL;
PyThreadState *_PyThreadState_Current = NULL;
PyThreadFrameGetter _PyThreadState_GetFrame = NULL;
PyInterpreterState *
PyInterpreterState_New(void)
{
PyInterpreterState *interp = PyMem_NEW(PyInterpreterState, 1);
if (interp != NULL) {
HEAD_INIT();
interp->modules = NULL;
interp->sysdict = NULL;
interp->builtins = NULL;
interp->tstate_head = NULL;
interp->codec_search_path = NULL;
interp->codec_search_cache = NULL;
interp->codec_error_registry = NULL;
#ifdef HAVE_DLOPEN
#ifdef RTLD_NOW
interp->dlopenflags = RTLD_NOW;
#else
interp->dlopenflags = RTLD_LAZY;
#endif
#endif
HEAD_LOCK();
interp->next = interp_head;
interp_head = interp;
HEAD_UNLOCK();
}
return interp;
}
void
PyInterpreterState_Clear(PyInterpreterState *interp)
{
PyThreadState *p;
HEAD_LOCK();
for (p = interp->tstate_head; p != NULL; p = p->next)
PyThreadState_Clear(p);
HEAD_UNLOCK();
ZAP(interp->codec_search_path);
ZAP(interp->codec_search_cache);
ZAP(interp->codec_error_registry);
ZAP(interp->modules);
ZAP(interp->sysdict);
ZAP(interp->builtins);
}
static void
zapthreads(PyInterpreterState *interp)
{
PyThreadState *p;
/* No need to lock the mutex here because this should only happen
when the threads are all really dead (XXX famous last words). */
while ((p = interp->tstate_head) != NULL) {
PyThreadState_Delete(p);
}
}
void
PyInterpreterState_Delete(PyInterpreterState *interp)
{
PyInterpreterState **p;
zapthreads(interp);
HEAD_LOCK();
for (p = &interp_head; ; p = &(*p)->next) {
if (*p == NULL)
Py_FatalError(
"PyInterpreterState_Delete: invalid interp");
if (*p == interp)
break;
}
if (interp->tstate_head != NULL)
Py_FatalError("PyInterpreterState_Delete: remaining threads");
*p = interp->next;
HEAD_UNLOCK();
PyMem_DEL(interp);
}
/* Default implementation for _PyThreadState_GetFrame */
static struct _frame *
threadstate_getframe(PyThreadState *self)
{
return self->frame;
}
PyThreadState *
PyThreadState_New(PyInterpreterState *interp)
{
PyThreadState *tstate = PyMem_NEW(PyThreadState, 1);
if (_PyThreadState_GetFrame == NULL)
_PyThreadState_GetFrame = threadstate_getframe;
if (tstate != NULL) {
tstate->interp = interp;
tstate->frame = NULL;
tstate->recursion_depth = 0;
tstate->tracing = 0;
tstate->use_tracing = 0;
tstate->tick_counter = 0;
tstate->gilstate_counter = 0;
tstate->dict = NULL;
tstate->curexc_type = NULL;
tstate->curexc_value = NULL;
tstate->curexc_traceback = NULL;
tstate->exc_type = NULL;
tstate->exc_value = NULL;
tstate->exc_traceback = NULL;
tstate->c_profilefunc = NULL;
tstate->c_tracefunc = NULL;
tstate->c_profileobj = NULL;
tstate->c_traceobj = NULL;
HEAD_LOCK();
tstate->next = interp->tstate_head;
interp->tstate_head = tstate;
HEAD_UNLOCK();
}
return tstate;
}
void
PyThreadState_Clear(PyThreadState *tstate)
{
if (Py_VerboseFlag && tstate->frame != NULL)
fprintf(stderr,
1997-08-20 23:28:19 -03:00
"PyThreadState_Clear: warning: thread still has a frame\n");
ZAP(tstate->frame);
ZAP(tstate->dict);
ZAP(tstate->curexc_type);
ZAP(tstate->curexc_value);
ZAP(tstate->curexc_traceback);
ZAP(tstate->exc_type);
ZAP(tstate->exc_value);
ZAP(tstate->exc_traceback);
tstate->c_profilefunc = NULL;
tstate->c_tracefunc = NULL;
ZAP(tstate->c_profileobj);
ZAP(tstate->c_traceobj);
}
/* Common code for PyThreadState_Delete() and PyThreadState_DeleteCurrent() */
static void
tstate_delete_common(PyThreadState *tstate)
{
PyInterpreterState *interp;
PyThreadState **p;
if (tstate == NULL)
Py_FatalError("PyThreadState_Delete: NULL tstate");
interp = tstate->interp;
if (interp == NULL)
Py_FatalError("PyThreadState_Delete: NULL interp");
HEAD_LOCK();
for (p = &interp->tstate_head; ; p = &(*p)->next) {
if (*p == NULL)
Py_FatalError(
"PyThreadState_Delete: invalid tstate");
if (*p == tstate)
break;
}
*p = tstate->next;
HEAD_UNLOCK();
PyMem_DEL(tstate);
}
void
PyThreadState_Delete(PyThreadState *tstate)
{
if (tstate == _PyThreadState_Current)
Py_FatalError("PyThreadState_Delete: tstate is still current");
tstate_delete_common(tstate);
}
#ifdef WITH_THREAD
void
PyThreadState_DeleteCurrent()
{
PyThreadState *tstate = _PyThreadState_Current;
if (tstate == NULL)
Py_FatalError(
"PyThreadState_DeleteCurrent: no current tstate");
_PyThreadState_Current = NULL;
tstate_delete_common(tstate);
PyEval_ReleaseLock();
}
#endif /* WITH_THREAD */
PyThreadState *
PyThreadState_Get(void)
{
if (_PyThreadState_Current == NULL)
Py_FatalError("PyThreadState_Get: no current thread");
return _PyThreadState_Current;
}
PyThreadState *
PyThreadState_Swap(PyThreadState *new)
{
PyThreadState *old = _PyThreadState_Current;
_PyThreadState_Current = new;
/* It should not be possible for more than one thread state
to be used for a thread. Check this the best we can in debug
builds.
*/
#if defined(Py_DEBUG) && defined(WITH_THREAD)
if (new) {
PyThreadState *check = PyGILState_GetThisThreadState();
if (check && check != new)
Py_FatalError("Invalid thread state for this thread");
}
#endif
return old;
}
/* An extension mechanism to store arbitrary additional per-thread state.
PyThreadState_GetDict() returns a dictionary that can be used to hold such
state; the caller should pick a unique key and store its state there. If
PyThreadState_GetDict() returns NULL, an exception has *not* been raised
and the caller should assume no per-thread state is available. */
PyObject *
PyThreadState_GetDict(void)
{
if (_PyThreadState_Current == NULL)
return NULL;
if (_PyThreadState_Current->dict == NULL) {
PyObject *d;
_PyThreadState_Current->dict = d = PyDict_New();
if (d == NULL)
PyErr_Clear();
}
return _PyThreadState_Current->dict;
}
/* Routines for advanced debuggers, requested by David Beazley.
Don't use unless you know what you are doing! */
PyInterpreterState *
PyInterpreterState_Head(void)
{
return interp_head;
}
PyInterpreterState *
PyInterpreterState_Next(PyInterpreterState *interp) {
return interp->next;
}
PyThreadState *
PyInterpreterState_ThreadHead(PyInterpreterState *interp) {
return interp->tstate_head;
}
PyThreadState *
PyThreadState_Next(PyThreadState *tstate) {
return tstate->next;
}
/* Python "auto thread state" API. */
#ifdef WITH_THREAD
/* Keep this as a static, as it is not reliable! It can only
ever be compared to the state for the *current* thread.
* If not equal, then it doesn't matter that the actual
value may change immediately after comparison, as it can't
possibly change to the current thread's state.
* If equal, then the current thread holds the lock, so the value can't
change until we yield the lock.
*/
static int
PyThreadState_IsCurrent(PyThreadState *tstate)
{
/* Must be the tstate for this thread */
assert(PyGILState_GetThisThreadState()==tstate);
/* On Windows at least, simple reads and writes to 32 bit values
are atomic.
*/
return tstate == _PyThreadState_Current;
}
/* The single PyInterpreterState used by this process'
GILState implementation
*/
static PyInterpreterState *autoInterpreterState = NULL;
static int autoTLSkey = 0;
/* Internal initialization/finalization functions called by
Py_Initialize/Py_Finalize
*/
void _PyGILState_Init(PyInterpreterState *i, PyThreadState *t)
{
assert(i && t); /* must init with a valid states */
autoTLSkey = PyThread_create_key();
autoInterpreterState = i;
/* Now stash the thread state for this thread in TLS */
PyThread_set_key_value(autoTLSkey, (void *)t);
assert(t->gilstate_counter==0); /* must be a new thread state */
t->gilstate_counter = 1;
}
void _PyGILState_Fini(void)
{
PyThread_delete_key(autoTLSkey);
autoTLSkey = 0;
autoInterpreterState = NULL;;
}
/* The public functions */
PyThreadState *PyGILState_GetThisThreadState(void)
{
if (autoInterpreterState==NULL || autoTLSkey==0)
return NULL;
return (PyThreadState *) PyThread_get_key_value(autoTLSkey);
}
PyGILState_STATE PyGILState_Ensure(void)
{
int current;
PyThreadState *tcur;
/* Note that we do not auto-init Python here - apart from
potential races with 2 threads auto-initializing, pep-311
spells out other issues. Embedders are expected to have
called Py_Initialize() and usually PyEval_InitThreads().
*/
assert(autoInterpreterState); /* Py_Initialize() hasn't been called! */
tcur = PyThread_get_key_value(autoTLSkey);
if (tcur==NULL) {
/* Create a new thread state for this thread */
tcur = PyThreadState_New(autoInterpreterState);
if (tcur==NULL)
Py_FatalError("Couldn't create thread-state for new thread");
PyThread_set_key_value(autoTLSkey, (void *)tcur);
current = 0; /* new thread state is never current */
} else
current = PyThreadState_IsCurrent(tcur);
if (!current)
PyEval_RestoreThread(tcur);
/* Update our counter in the thread-state - no need for locks:
- tcur will remain valid as we hold the GIL.
- the counter is safe as we are the only thread "allowed"
to modify this value
*/
tcur->gilstate_counter++;
return current ? PyGILState_LOCKED : PyGILState_UNLOCKED;
}
void PyGILState_Release(PyGILState_STATE oldstate)
{
PyThreadState *tcur = PyThread_get_key_value(autoTLSkey);
if (tcur==NULL)
Py_FatalError("auto-releasing thread-state, "
"but no thread-state for this thread");
/* We must hold the GIL and have our thread state current */
/* XXX - remove the check - the assert should be fine,
but while this is very new (April 2003), the extra check
by release-only users can't hurt.
*/
if (!PyThreadState_IsCurrent(tcur))
Py_FatalError("This thread state must be current when releasing");
assert (PyThreadState_IsCurrent(tcur));
tcur->gilstate_counter -= 1;
assert (tcur->gilstate_counter >= 0); /* illegal counter value */
/* If we are about to destroy this thread-state, we must
clear it while the lock is held, as destructors may run
*/
if (tcur->gilstate_counter==0) {
/* can't have been locked when we created it */
assert(oldstate==PyGILState_UNLOCKED);
PyThreadState_Clear(tcur);
}
/* Release the lock if necessary */
if (oldstate==PyGILState_UNLOCKED)
PyEval_ReleaseThread(tcur);
/* Now complete destruction of the thread if necessary */
if (tcur->gilstate_counter==0) {
/* Delete this thread from our TLS */
PyThread_delete_key_value(autoTLSkey);
/* Delete the thread-state */
PyThreadState_Delete(tcur);
}
}
#endif /* WITH_THREAD */