cpython/Python/pystate.c

/* Thread and interpreter state structures and their interfaces */

#include "Python.h"

#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;


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->checkinterval = 10;
		interp->tstate_head = NULL;

		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->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);
}


PyThreadState *
PyThreadState_New(PyInterpreterState *interp)
{
	PyThreadState *tstate = PyMem_NEW(PyThreadState, 1);

	if (tstate != NULL) {
		tstate->interp = interp;

		tstate->frame = NULL;
		tstate->recursion_depth = 0;
		tstate->ticker = 0;
		tstate->tracing = 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->sys_profilefunc = NULL;
		tstate->sys_tracefunc = 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,
		  "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);

	ZAP(tstate->sys_profilefunc);
	ZAP(tstate->sys_tracefunc);
}


/* 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;

	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 been raised (most
   likely MemoryError) and the caller should pass on the exception. */

PyObject *
PyThreadState_GetDict(void)
{
	if (_PyThreadState_Current == NULL)
		Py_FatalError("PyThreadState_GetDict: no current thread");

	if (_PyThreadState_Current->dict == NULL)
		_PyThreadState_Current->dict = PyDict_New();
	return _PyThreadState_Current->dict;
}