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

#include "Python.h"

/* --------------------------------------------------------------------------

CAUTION

Always use malloc() and free() directly in this file.  A number of these

functions are advertised as safe to call when the GIL isn't held, and in

a debug build Python redirects (e.g.) PyMem_NEW (etc) to Python's debugging

obmalloc functions.  Those aren't thread-safe (they rely on the GIL to avoid

the expense of doing their own locking).

-------------------------------------------------------------------------- */

#ifdef HAVE_DLOPEN

#ifdef HAVE_DLFCN_H

#include <dlfcn.h>

#endif

#ifndef RTLD_LAZY

#define RTLD_LAZY 1

#endif

#endif

#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)

#ifdef __cplusplus

extern "C" {

#endif

/* The single PyInterpreterState used by this process'

   GILState implementation

*/

static PyInterpreterState *autoInterpreterState = NULL;

static int autoTLSkey = 0;

#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;

#ifdef WITH_THREAD

static void _PyGILState_NoteThreadState(PyThreadState* tstate);

#endif

PyInterpreterState *

PyInterpreterState_New(void)

{

	PyInterpreterState *interp = (PyInterpreterState *)

				     malloc(sizeof(PyInterpreterState));

	if (interp != NULL) {

		HEAD_INIT();

#ifdef WITH_THREAD

		if (head_mutex == NULL)

			Py_FatalError("Can't initialize threads for interpreter");

#endif

		interp->modules = NULL;

		interp->modules_reloading = 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

#ifdef WITH_TSC

		interp->tscdump = 0;

#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();

	Py_CLEAR(interp->codec_search_path);

	Py_CLEAR(interp->codec_search_cache);

	Py_CLEAR(interp->codec_error_registry);

	Py_CLEAR(interp->modules);

	Py_CLEAR(interp->modules_reloading);

	Py_CLEAR(interp->sysdict);

	Py_CLEAR(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();

	free(interp);

}

/* Default implementation for _PyThreadState_GetFrame */

static struct _frame *

threadstate_getframe(PyThreadState *self)

{

	return self->frame;

}

PyThreadState *

PyThreadState_New(PyInterpreterState *interp)

{

	PyThreadState *tstate = (PyThreadState *)malloc(sizeof(PyThreadState));

	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->async_exc = NULL;

#ifdef WITH_THREAD

		tstate->thread_id = PyThread_get_thread_ident();

#else

		tstate->thread_id = 0;

#endif

		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;

#ifdef WITH_THREAD

		_PyGILState_NoteThreadState(tstate);

#endif

		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");

	Py_CLEAR(tstate->frame);

	Py_CLEAR(tstate->dict);

	Py_CLEAR(tstate->async_exc);

	Py_CLEAR(tstate->curexc_type);

	Py_CLEAR(tstate->curexc_value);

	Py_CLEAR(tstate->curexc_traceback);

	Py_CLEAR(tstate->exc_type);

	Py_CLEAR(tstate->exc_value);

	Py_CLEAR(tstate->exc_traceback);

	tstate->c_profilefunc = NULL;

	tstate->c_tracefunc = NULL;

	Py_CLEAR(tstate->c_profileobj);

	Py_CLEAR(tstate->c_traceobj);

}

/* Common code for PyThreadState_Delete() and PyThreadState_DeleteCurrent() */

static void

tstate_delete_common(PyThreadState *tstate)

{

	PyInterpreterState *interp;

	PyThreadState **p;

	PyThreadState *prev_p = NULL;

	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;

		/* Sanity check.  These states should never happen but if

		 * they do we must abort.  Otherwise we'll end up spinning in

		 * in a tight loop with the lock held.  A similar check is done

		 * in thread.c find_key().  */

		if (*p == prev_p)

			Py_FatalError(

				"PyThreadState_Delete: small circular list(!)"

                                " and tstate not found.");

		prev_p = *p;

		if ((*p)->next == interp->tstate_head)

			Py_FatalError(

				"PyThreadState_Delete: circular list(!) and"

                                " tstate not found.");

	}

	*p = tstate->next;

	HEAD_UNLOCK();

	free(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

	if (autoTLSkey && PyThread_get_key_value(autoTLSkey) == tstate)

		PyThread_delete_key_value(autoTLSkey);

#endif /* WITH_THREAD */

}

#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);

	if (autoTLSkey && PyThread_get_key_value(autoTLSkey) == tstate)

		PyThread_delete_key_value(autoTLSkey);

	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 *newts)

{

	PyThreadState *oldts = _PyThreadState_Current;

	_PyThreadState_Current = newts;

	/* 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 (newts) {

		/* This can be called from PyEval_RestoreThread(). Similar

		   to it, we need to ensure errno doesn't change.

		*/

		int err = errno;

		PyThreadState *check = PyGILState_GetThisThreadState();

		if (check && check->interp == newts->interp && check != newts)

			Py_FatalError("Invalid thread state for this thread");

		errno = err;

	}

#endif

	return oldts;

}

/* 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;

}

/* Asynchronously raise an exception in a thread.

   Requested by Just van Rossum and Alex Martelli.

   To prevent naive misuse, you must write your own extension

   to call this, or use ctypes.  Must be called with the GIL held.

   Returns the number of tstates modified (normally 1, but 0 if `id` didn't

   match any known thread id).  Can be called with exc=NULL to clear an

   existing async exception.  This raises no exceptions. */

int

PyThreadState_SetAsyncExc(long id, PyObject *exc) {

	PyThreadState *tstate = PyThreadState_GET();

	PyInterpreterState *interp = tstate->interp;

	PyThreadState *p;

	/* Although the GIL is held, a few C API functions can be called

	 * without the GIL held, and in particular some that create and

	 * destroy thread and interpreter states.  Those can mutate the

	 * list of thread states we're traversing, so to prevent that we lock

	 * head_mutex for the duration.

	 */

	HEAD_LOCK();

	for (p = interp->tstate_head; p != NULL; p = p->next) {

		if (p->thread_id == id) {

			/* Tricky:  we need to decref the current value

			 * (if any) in p->async_exc, but that can in turn

			 * allow arbitrary Python code to run, including

			 * perhaps calls to this function.  To prevent

			 * deadlock, we need to release head_mutex before

			 * the decref.

			 */

			PyObject *old_exc = p->async_exc;

			Py_XINCREF(exc);

			p->async_exc = exc;

			HEAD_UNLOCK();

			Py_XDECREF(old_exc);

			return 1;

		}

	}

	HEAD_UNLOCK();

	return 0;

}

/* 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;

}

/* The implementation of sys._current_frames().  This is intended to be

   called with the GIL held, as it will be when called via

   sys._current_frames().  It's possible it would work fine even without

   the GIL held, but haven't thought enough about that.

*/

PyObject *

_PyThread_CurrentFrames(void)

{

	PyObject *result;

	PyInterpreterState *i;

	result = PyDict_New();

	if (result == NULL)

		return NULL;

	/* for i in all interpreters:

	 *     for t in all of i's thread states:

	 *          if t's frame isn't NULL, map t's id to its frame

	 * Because these lists can mutute even when the GIL is held, we

	 * need to grab head_mutex for the duration.

	 */

	HEAD_LOCK();

	for (i = interp_head; i != NULL; i = i->next) {

		PyThreadState *t;

		for (t = i->tstate_head; t != NULL; t = t->next) {

			PyObject *id;

			int stat;

			struct _frame *frame = t->frame;

			if (frame == NULL)

				continue;

			id = PyInt_FromLong(t->thread_id);

			if (id == NULL)

				goto Fail;

			stat = PyDict_SetItem(result, id, (PyObject *)frame);

			Py_DECREF(id);

			if (stat < 0)

				goto Fail;

		}

	}

	HEAD_UNLOCK();

	return result;

 Fail:

 	HEAD_UNLOCK();

 	Py_DECREF(result);

 	return NULL;

}

/* 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;

}

/* Internal initialization/finalization functions called by

   Py_Initialize/Py_Finalize

*/

void

_PyGILState_Init(PyInterpreterState *i, PyThreadState *t)

{

	assert(i && t); /* must init with valid states */

	autoTLSkey = PyThread_create_key();

	autoInterpreterState = i;

	assert(PyThread_get_key_value(autoTLSkey) == NULL);

	assert(t->gilstate_counter == 0);

	_PyGILState_NoteThreadState(t);

}

void

_PyGILState_Fini(void)

{

	PyThread_delete_key(autoTLSkey);

	autoTLSkey = 0;

	autoInterpreterState = NULL;

}

/* When a thread state is created for a thread by some mechanism other than

   PyGILState_Ensure, it's important that the GILState machinery knows about

   it so it doesn't try to create another thread state for the thread (this is

   a better fix for SF bug #1010677 than the first one attempted).

*/

static void